oxi/store/

settings.rs

//! Settings management for oxi CLI
//!
//! Settings are loaded in layers (later layers override earlier):
//! 1. Built-in defaults
//! 2. Global config: `~/.oxi/settings.toml`
//! 3. Project config: `.oxi/settings.toml` (walked up to repo root)
//! 4. Environment variables (`OXI_*` prefix)
//! 5. CLI arguments
//!
//! Migration is handled via a `version` field in the config file.

use anyhow::{Context, Result};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::env;
use std::fs;
use std::path::{Path, PathBuf};

/// Current settings format version.
///
/// Version history:
/// - 4: dynamic_models field + last_used_model/provider split
/// - 5: output_languages field (TUI-only language policy)
/// - 6: language_policy_enabled field (master toggle, default OFF)
const SETTINGS_VERSION: u32 = 6;

/// Known output channels for the TUI language policy.
///
/// `(key, prompt_label)` — `prompt_label` is the human-readable
/// phrase used when building the system prompt directive.
///
/// New channels can be added by the user in `settings.toml`; the
/// `KNOWN_CHANNELS` list is only the validation whitelist and the
/// prompt-rendering label table. The runtime policy generator
/// (`crate::prompt::system_prompt::language_directive`) walks this
/// list to render each non-auto channel.
pub const KNOWN_CHANNELS: &[(&str, &str)] = &[
    ("response", "Your conversational responses to the user"),
    (
        "code_comment",
        "Code comments you write (//, /* */, #, etc.)",
    ),
    (
        "documentation",
        "Documentation (markdown files, README, AGENTS.md, doc comments)",
    ),
    ("commit_message", "Git commit messages (subject + body)"),
];

/// Known language codes for the TUI language policy.
///
/// `(code, display_label)` — `code` is the ISO 639-1 value stored
/// in `settings.toml`; `display_label` is shown in the UI and used
/// in the rendered prompt directive.
///
/// `"auto"` is the special "match user's input language" sentinel
/// (see `crate::prompt::system_prompt::language_directive`).
/// Unknown codes are accepted at load time (with a warning) so that
/// users can add languages without code changes.
pub const KNOWN_LANGS: &[(&str, &str)] = &[
    ("auto", "Auto (match user)"),
    ("en", "English"),
    ("ko", "Korean (한국어)"),
    ("ja", "Japanese (日本語)"),
    ("zh", "Chinese (中文)"),
    ("es", "Spanish"),
    ("fr", "French"),
    ("de", "German"),
];

/// Environment variable prefix for oxi settings.
/// Keep: reserved for future env-based config loading (e.g. OXI_API_KEY).
#[allow(dead_code)]
const ENV_PREFIX: &str = "OXI_";

/// Thinking level for agent responses
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Default)]
#[serde(rename_all = "snake_case")]
pub enum ThinkingLevel {
    /// Extended reasoning disabled (default).
    #[default]
    Off,
    /// Minimal reasoning.
    Minimal,
    /// Low reasoning.
    Low,
    /// Medium reasoning.
    Medium,
    /// High reasoning.
    High,
    /// Very high reasoning.
    XHigh,
}

/// A custom OpenAI-compatible provider configuration.
///
/// Custom providers are loaded from `~/.oxi/settings.toml` via `[[custom_provider]]` sections
/// and registered at runtime so that models like `minimax/minimax-m2.5` can be used directly.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CustomProvider {
    /// Unique provider name (e.g. `"minimax"`).
    pub name: String,
    /// Base URL of the OpenAI-compatible API (e.g. `"https://api.minimax.chat/v1"`).
    pub base_url: String,
    /// Environment variable name that holds the API key (e.g. `"MINIMAX_API_KEY"`).
    pub api_key_env: String,
    /// API dialect: `"openai-completions"` or `"openai-responses"`.
    #[serde(default = "default_custom_provider_api")]
    pub api: String,
}

fn default_custom_provider_api() -> String {
    "openai-completions".to_string()
}

/// Application settings
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Settings {
    // ── Version (for migration) ──────────────────────────────────────
    /// Settings format version. Used for automatic migration.
    #[serde(default)]
    pub version: u32,

    // ── Core LLM settings ───────────────────────────────────────────
    /// Thinking level for agent responses
    #[serde(default = "default_thinking_level")]
    pub thinking_level: ThinkingLevel,

    /// Color theme (e.g., "default", "monokai", "dracula")
    #[serde(default = "default_theme")]
    pub theme: String,

    /// Deprecated: use `last_used_model` instead. Kept for serde backward compat.
    #[serde(default, skip_serializing)]
    pub default_model: Option<String>,

    /// Deprecated: use `last_used_provider` instead. Kept for serde backward compat.
    #[serde(default, skip_serializing)]
    pub default_provider: Option<String>,

    /// Model selected by the user (last used = current default).
    /// Set during onboarding and updated every time the user switches model.
    #[serde(default)]
    pub last_used_model: Option<String>,

    /// Provider for the last used model.
    #[serde(default)]
    pub last_used_provider: Option<String>,

    /// Max tokens for responses
    pub max_tokens: Option<u32>,

    /// Temperature for generation (0.0–2.0)
    pub temperature: Option<f32>,

    /// Default temperature as f64 (higher precision, takes precedence over `temperature`)
    pub default_temperature: Option<f64>,

    /// Maximum tokens for generation (usize variant, takes precedence over `max_tokens`)
    pub max_response_tokens: Option<usize>,

    // ── Session settings ─────────────────────────────────────────────
    /// Session history size (entries to keep in memory)
    #[serde(default = "default_session_history_size")]
    pub session_history_size: usize,

    /// Directory for storing sessions (default: `~/.oxi/sessions`)
    pub session_dir: Option<PathBuf>,

    // ── Behaviour flags ──────────────────────────────────────────────
    /// Whether to stream responses
    #[serde(default = "default_true")]
    pub stream_responses: bool,

    /// Whether extensions are enabled
    #[serde(default = "default_true")]
    pub extensions_enabled: bool,

    /// Whether to auto-compact conversations that exceed context window
    #[serde(default = "default_true")]
    pub auto_compaction: bool,

    /// Built-in tools to disable (by name, e.g. `["web_search", "github_search"]`).
    /// All tools are enabled by default; list tools here to turn them off.
    #[serde(default)]
    pub disabled_tools: Vec<String>,

    // ── Timeouts ─────────────────────────────────────────────────────
    /// Timeout in seconds for tool execution
    #[serde(default = "default_tool_timeout")]
    pub tool_timeout_seconds: u64,

    // ── Resource lists (managed by `oxi config`) ────────────────────
    /// List of extension paths or npm package sources to load
    #[serde(default)]
    pub extensions: Vec<String>,

    /// List of skill paths or npm package sources to load
    #[serde(default)]
    pub skills: Vec<String>,

    /// List of prompt template paths to load
    #[serde(default)]
    pub prompts: Vec<String>,

    /// List of theme paths to load
    #[serde(default)]
    pub themes: Vec<String>,

    // ── Custom OpenAI-compatible providers ──────────────────────────────
    /// Registered custom providers (loaded from `[[custom_provider]]` TOML sections).
    #[serde(default)]
    pub custom_providers: Vec<CustomProvider>,

    // ── Dynamic model cache ─────────────────────────────────────────────
    /// Cached model lists fetched from provider `/models` endpoints.
    /// Key is the provider name, value is a list of model IDs.
    /// Updated when API keys are entered in setup wizard or on demand.
    #[serde(default)]
    pub dynamic_models: HashMap<String, Vec<String>>,

    // ── Multi-provider routing ─────────────────────────────────────────
    /// Enable automatic complexity-based routing
    #[serde(default = "default_false")]
    pub enable_routing: bool,

    /// Router profile name to use (e.g., "auto", "balanced").
    #[serde(default)]
    pub router_profile: Option<String>,

    /// Prefer cost-efficient models when routing
    #[serde(default = "default_true")]
    pub prefer_cost_efficient: bool,

    /// Fallback chain: ordered list of model IDs to try on failure
    #[serde(default)]
    pub fallback_chain: Vec<String>,

    /// Whether to use provider fallback on errors (false = fail fast)
    #[serde(default = "default_true")]
    pub enable_fallback: bool,

    /// Disable automatic fallback (same as enable_fallback = false)
    #[serde(default)]
    pub disable_fallback: bool,

    /// Circuit breaker failure threshold per provider
    #[serde(default = "default_circuit_failure_threshold")]
    pub circuit_breaker_failure_threshold: u32,

    /// Circuit breaker open duration in seconds
    #[serde(default = "default_circuit_open_duration_secs")]
    pub circuit_breaker_open_duration_secs: u64,

    // ── Keybindings ────────────────────────────────────────────────────
    /// User-defined keybinding overrides.
    /// Format: `{ "ActionName": ["Ctrl+x", "Alt+y"] }`
    /// Actions are matched case-insensitively to the Action enum in oxi-tui.
    #[serde(default)]
    pub keybindings: HashMap<String, Vec<String>>,

    // ── TUI output language policy (TUI-only) ─────────────────────────
    /// Per-channel output language for the TUI agent loop.
    ///
    /// Maps a channel key (e.g. `"response"`, `"code_comment"`,
    /// `"documentation"`, `"commit_message"`) to a language code
    /// (e.g. `"en"`, `"ko"`, or `"auto"`).
    ///
    /// **Scope:** This setting is consumed exclusively by
    /// `crate::app::agent_session_runtime::build_system_prompt` (the
    /// TUI session build path). The `lib.rs` App build path used by
    /// `oxi --print` and RPC mode **does not** inject the policy,
    /// so this setting is silently ignored in non-TUI modes.
    ///
    /// **Default:** Empty map. Every channel defaults to `"auto"`
    /// (match the most recent user message language), preserving
    /// the previous behavior. Set a channel to a non-`"auto"`
    /// value to fix its output language.
    ///
    /// **Extension map:** User-defined channels beyond the four in
    /// `KNOWN_CHANNELS` are accepted (e.g. `pr_description = "en"`).
    /// Unknown channels fall back to using the raw key as the label
    /// in the rendered directive, and the model typically still
    /// understands from context.
    ///
    /// **Strong default, NOT a hard guarantee.** This setting drives
    /// a prompt-level "MUST" directive at the end of the system
    /// prompt and a `"Focus areas:"` instruction passed to the
    /// compaction summarizer. Both are prompt-level signals — the
    /// model can still occasionally violate the policy when:
    ///
    ///   - the context grows long and the directive is "lost in the
    ///     middle";
    ///   - tool output is echoed verbatim without translation;
    ///   - subagent summarization under a different framing weakens
    ///     the instruction (see `build_compaction_instruction` for
    ///     the exact framing caveat).
    ///
    /// If a 100% guarantee is required, additional layers (tool
    /// output wrapping, response post-processing) are needed — out
    /// of scope for this MVP.
    ///
    /// **Validation:** Unknown language codes are logged at warn
    /// level and kept (so users can add languages without code
    /// changes). Channel keys are not validated — see "Extension
    /// map" above.
    #[serde(default)]
    pub output_languages: HashMap<String, String>,

    // ── TUI language policy master toggle (v6) ────────────────────────
    /// Master switch for the TUI output language policy.
    ///
    /// **Default: `false` (opt-in).** Even with a non-empty
    /// `output_languages` map, the policy is **not** injected into
    /// the system prompt or compaction instruction unless this is
    /// `true`. Users must toggle it ON in the `/settings` overlay
    /// for the policy to take effect.
    ///
    /// **Why opt-in (not opt-out):** keeps the pre-feature behavior
    /// intact for users who never touch language settings, while
    /// making the feature discoverable through the overlay toggle.
    /// Users who configured `output_languages` in v5 will see their
    /// channel mappings preserved on disk, but disabled until they
    /// flip this switch.
    ///
    /// **Scope:** TUI-only. `oxi --print` and RPC mode ignore the
    /// policy regardless of this flag (see AGENTS.md pitfalls).
    #[serde(default = "default_false")]
    pub language_policy_enabled: bool,
}

fn default_theme() -> String {
    "default".to_string()
}

fn default_thinking_level() -> ThinkingLevel {
    ThinkingLevel::Medium
}

fn default_session_history_size() -> usize {
    100
}

fn default_true() -> bool {
    true
}

fn default_false() -> bool {
    false
}

fn default_circuit_failure_threshold() -> u32 {
    5
}

fn default_circuit_open_duration_secs() -> u64 {
    30
}

fn default_tool_timeout() -> u64 {
    120
}

impl Default for Settings {
    fn default() -> Self {
        Self {
            version: SETTINGS_VERSION,
            thinking_level: ThinkingLevel::Medium,
            theme: default_theme(),
            last_used_model: None,
            last_used_provider: None,
            default_model: None,
            default_provider: None,
            max_tokens: None,
            temperature: None,
            default_temperature: None,
            max_response_tokens: None,
            session_history_size: default_session_history_size(),
            session_dir: None,
            stream_responses: true,
            extensions_enabled: true,
            auto_compaction: true,
            disabled_tools: Vec::new(),
            tool_timeout_seconds: default_tool_timeout(),
            extensions: Vec::new(),
            skills: Vec::new(),
            prompts: Vec::new(),
            themes: Vec::new(),
            custom_providers: Vec::new(),
            dynamic_models: HashMap::new(),
            // Multi-provider routing defaults
            enable_routing: false,
            router_profile: None,
            prefer_cost_efficient: true,
            fallback_chain: Vec::new(),
            enable_fallback: true,
            disable_fallback: false,
            circuit_breaker_failure_threshold: 5,
            circuit_breaker_open_duration_secs: 30,
            keybindings: HashMap::new(),
            output_languages: HashMap::new(),
            language_policy_enabled: false,
        }
    }
}

impl Settings {
    // ── Paths ────────────────────────────────────────────────────────

    /// Get the global settings directory path (`~/.oxi`).
    pub fn settings_dir() -> Result<PathBuf> {
        let base = dirs::home_dir().context("Cannot determine home directory")?;
        Ok(base.join(".oxi"))
    }

    /// Get the global settings TOML file path (`~/.oxi/settings.toml`).
    pub fn settings_toml_path() -> Result<PathBuf> {
        Ok(Self::settings_dir()?.join("settings.toml"))
    }

    /// Get the global settings JSON file path (`~/.oxi/settings.json`).
    pub fn settings_json_path() -> Result<PathBuf> {
        Ok(Self::settings_dir()?.join("settings.json"))
    }

    /// Get the global settings file path (JSON takes priority).
    ///
    /// Returns the path to the settings file that should be used.
    /// If both JSON and TOML exist, JSON is returned (takes priority).
    /// If only one exists, that path is returned.
    /// If neither exists, returns the JSON path by default.
    pub fn settings_path() -> Result<PathBuf> {
        let json_path = Self::settings_json_path()?;
        let toml_path = Self::settings_toml_path()?;

        if json_path.exists() && toml_path.exists() {
            // Both exist: JSON takes priority
            tracing::debug!("Both settings.json and settings.toml exist, using settings.json");
            return Ok(json_path);
        }

        if json_path.exists() {
            return Ok(json_path);
        }

        if toml_path.exists() {
            return Ok(toml_path);
        }

        // Neither exists: default to JSON
        Ok(json_path)
    }

    /// Get the effective settings file path, preferring the specified format.
    ///
    /// If `prefer_json` is true, checks JSON first; otherwise checks TOML first.
    /// Returns the first existing file, or the preferred path if neither exists.
    pub fn settings_path_with_preference(prefer_json: bool) -> Result<PathBuf> {
        let json_path = Self::settings_json_path()?;
        let toml_path = Self::settings_toml_path()?;

        let (primary, secondary) = if prefer_json {
            (&json_path, &toml_path)
        } else {
            (&toml_path, &json_path)
        };

        if primary.exists() {
            return Ok(primary.clone());
        }

        if secondary.exists() {
            return Ok(secondary.clone());
        }

        // Neither exists: return preferred path
        Ok(primary.clone())
    }

    /// Detect the settings file format from its path.
    pub fn detect_format(path: &Path) -> SettingsFormat {
        match path.extension().and_then(|e| e.to_str()) {
            Some("json") => SettingsFormat::Json,
            Some("toml") => SettingsFormat::Toml,
            _ => SettingsFormat::Json, // Default to JSON for unknown extensions
        }
    }

    /// Get the project-local settings file path.
    ///
    /// Searches for `.oxi/settings.json` first, then `.oxi/settings.toml`.
    /// Returns the first one found, or None if neither exists.
    pub fn find_project_settings(start_dir: &std::path::Path) -> Option<PathBuf> {
        let mut dir = start_dir.to_path_buf();
        loop {
            // Check JSON first (priority), then TOML
            let json_candidate = dir.join(".oxi").join("settings.json");
            if json_candidate.exists() {
                return Some(json_candidate);
            }

            let toml_candidate = dir.join(".oxi").join("settings.toml");
            if toml_candidate.exists() {
                return Some(toml_candidate);
            }

            if !dir.pop() {
                return None;
            }
        }
    }

    /// Resolve the effective session directory.
    ///
    /// Priority: `session_dir` field → `~/.oxi/sessions`.
    pub fn effective_session_dir(&self) -> Result<PathBuf> {
        if let Some(ref dir) = self.session_dir {
            return Ok(dir.clone());
        }
        Ok(Self::settings_dir()?.join("sessions"))
    }

    // ── Loading ──────────────────────────────────────────────────────

    /// Load settings, applying all layers:
    ///
    /// 1. Built-in defaults
    /// 2. Global `~/.oxi/settings.toml`
    /// 3. Project `.oxi/settings.toml`
    /// 4. Environment variable overrides
    ///
    /// # Examples
    ///
    /// ```ignore
    /// use oxi_cli::Settings;
    ///
    /// let settings = Settings::load().expect("Failed to load settings");
    /// println!("Using model: {}", settings.effective_model(None));
    /// ```
    pub fn load() -> Result<Self> {
        Self::load_from_cwd()
    }

    /// Load settings with an explicit working directory for project config discovery.
    pub fn load_from(dir: &std::path::Path) -> Result<Self> {
        // 1. Start from defaults
        let mut settings = Settings::default();

        // 2. Layer global config
        if let Ok(global_path) = Self::settings_path()
            && global_path.exists()
        {
            settings = Self::layer_file(&settings, &global_path)?;
        }

        // 3. Layer project config
        if let Some(project_path) = Self::find_project_settings(dir) {
            settings = Self::layer_file(&settings, &project_path)?;
        }

        // 4. Layer environment variables
        settings.apply_env();

        // 5. Run migration if needed
        settings = Self::migrate(settings)?;

        // 6. Validate TUI-specific language policy
        settings.validate_output_languages();

        Ok(settings)
    }

    /// Warn on unknown `output_languages` language codes. Channel
    /// keys are **not** validated: any channel (known or user-defined)
    /// is accepted so users can add new channels in `settings.toml`
    /// without code changes. `KNOWN_CHANNELS` provides a label table
    /// for the prompt directive; unknown channels fall back to using
    /// the raw key as the label.
    fn validate_output_languages(&mut self) {
        if self.output_languages.is_empty() {
            return;
        }
        let known_langs: std::collections::HashSet<&str> =
            KNOWN_LANGS.iter().map(|(k, _)| *k).collect();

        for (channel, lang) in &self.output_languages {
            if !known_langs.contains(lang.as_str()) {
                tracing::warn!(
                    "Unknown output_languages language code '{}' for channel '{}'. \
                     Keeping as-is (the model will likely understand).",
                    lang,
                    channel
                );
            }
        }
    }

    /// Convenience: load from current working directory.
    pub fn load_from_cwd() -> Result<Self> {
        let cwd = env::current_dir().context("Cannot determine current directory")?;
        Self::load_from(&cwd)
    }

    /// Parse a settings file (TOML or JSON) and overlay its values onto `base`.
    ///
    /// The format is auto-detected based on the file extension.
    /// Fields present in the file replace those in `base`; absent fields
    /// are left untouched.
    fn layer_file(base: &Settings, path: &std::path::Path) -> Result<Settings> {
        let content = fs::read_to_string(path)
            .with_context(|| format!("Failed to read settings from {}", path.display()))?;

        let format = Self::detect_format(path);
        let overlay: serde_json::Value = match format {
            SettingsFormat::Toml => {
                let toml_value: toml::Value = toml::from_str(&content).with_context(|| {
                    format!("Failed to parse TOML settings from {}", path.display())
                })?;
                // Convert TOML to JSON Value for uniform merging
                toml_value_to_json(toml_value)
            }
            SettingsFormat::Json => serde_json::from_str(&content).with_context(|| {
                format!("Failed to parse JSON settings from {}", path.display())
            })?,
        };

        // Re-serialize the base to JSON, merge with the overlay, then
        // deserialize back. This gives correct "only override what's
        // present" semantics.
        let base_json =
            serde_json::to_value(base).context("Failed to serialize base settings for merge")?;

        let merged = merge_json_values(base_json, overlay);
        let result: Settings =
            serde_json::from_value(merged).context("Failed to deserialize merged settings")?;

        Ok(result)
    }

    // ── Environment variables ────────────────────────────────────────

    /// Apply environment variable overrides in-place.
    ///
    /// DEPRECATED: Environment variable overrides are being phased out in favor
    /// of file-based configuration (`~/.oxi/settings.toml`). This method is
    /// kept for CI/CD compatibility but should not be relied upon for local
    /// development. Use `oxi config set` or `oxi setup` instead.
    ///
    /// Supported variables (CI/CD only):
    ///
    /// | Env var                    | Setting                |
    /// |---------------------------|------------------------|
    /// | `OXI_MODEL`               | `default_model`        |
    /// | `OXI_PROVIDER`            | `default_provider`     |
    /// | `OXI_THINKING`            | `thinking_level`       |
    /// | `OXI_THEME`               | `theme`                |
    /// | `OXI_MAX_TOKENS`          | `max_tokens`           |
    /// | `OXI_TEMPERATURE`         | `default_temperature`  |
    /// | `OXI_SESSION_DIR`         | `session_dir`          |
    /// | `OXI_STREAM`              | `stream_responses`     |
    /// | `OXI_EXTENSIONS_ENABLED`  | `extensions_enabled`   |
    /// | `OXI_AUTO_COMPACTION`     | `auto_compaction`      |
    /// | `OXI_TOOL_TIMEOUT`        | `tool_timeout_seconds` |
    /// | `OXI_DISABLED_TOOLS`      | `disabled_tools`       |
    #[allow(dead_code)]
    pub fn apply_env(&mut self) {
        // No-op: environment variable overrides are disabled.
        // All configuration should come from settings.toml / settings.json.
        // This method is kept for backward compatibility but does nothing.
    }

    /// Build a `Settings` instance from **only** environment variables
    /// (all other fields stay at defaults).
    ///
    /// DEPRECATED: Returns defaults since env overrides are disabled.
    /// Use `Settings::load()` to load from settings.toml instead.
    #[allow(dead_code)]
    pub fn from_env() -> Self {
        Self::default()
    }

    // ── Persistence ──────────────────────────────────────────────────

    /// Save settings to the global config file.
    ///
    /// Uses the format of the existing file if present, otherwise saves as JSON.
    /// Preserves backward compatibility with existing TOML files.
    pub fn save(&self) -> Result<()> {
        let dir = Self::settings_dir()?;
        let path = Self::settings_path()?;

        if !dir.exists() {
            fs::create_dir_all(&dir).with_context(|| {
                format!("Failed to create settings directory {}", dir.display())
            })?;
        }

        let format = Self::detect_format(&path);
        let content = Self::serialize_for_format(self, format)?;

        // Atomic write: write to temp file first, then rename
        let tmp_path = path.with_extension("tmp");
        fs::write(&tmp_path, &content)
            .with_context(|| format!("Failed to write settings to {}", tmp_path.display()))?;
        fs::rename(&tmp_path, &path)
            .with_context(|| format!("Failed to rename settings to {}", path.display()))?;

        Ok(())
    }

    /// Save settings to a specific path, using the format determined by the file extension.
    pub fn save_to(&self, path: &Path) -> Result<()> {
        if let Some(parent) = path.parent()
            && !parent.exists()
        {
            fs::create_dir_all(parent)
                .with_context(|| format!("Failed to create directory {}", parent.display()))?;
        }

        let format = Self::detect_format(path);
        let content = Self::serialize_for_format(self, format)?;

        // Atomic write
        let tmp_path = path.with_extension("tmp");
        fs::write(&tmp_path, &content)
            .with_context(|| format!("Failed to write settings to {}", tmp_path.display()))?;
        fs::rename(&tmp_path, path)
            .with_context(|| format!("Failed to rename settings to {}", path.display()))?;

        Ok(())
    }

    /// Save settings to the project-local config file.
    ///
    /// Uses the format of the existing file if present, otherwise saves as JSON.
    pub fn save_project(&self, project_dir: &std::path::Path) -> Result<()> {
        let dir = project_dir.join(".oxi");

        if !dir.exists() {
            fs::create_dir_all(&dir).with_context(|| {
                format!(
                    "Failed to create project settings directory {}",
                    dir.display()
                )
            })?;
        }

        // Check if a settings file already exists in project
        let json_path = dir.join("settings.json");
        let toml_path = dir.join("settings.toml");

        let path = if json_path.exists() {
            &json_path
        } else if toml_path.exists() {
            &toml_path
        } else {
            // Default to JSON for new files
            &json_path
        };

        let format = Self::detect_format(path);
        let content = Self::serialize_for_format(self, format)?;

        // Atomic write
        let tmp_path = path.with_extension("tmp");
        fs::write(&tmp_path, &content)
            .with_context(|| format!("Failed to write settings to {}", tmp_path.display()))?;
        fs::rename(&tmp_path, path)
            .with_context(|| format!("Failed to rename settings to {}", path.display()))?;

        Ok(())
    }

    /// Serialize settings to a string in the specified format.
    pub fn serialize_for_format(settings: &Settings, format: SettingsFormat) -> Result<String> {
        match format {
            SettingsFormat::Toml => {
                toml::to_string_pretty(settings).context("Failed to serialize settings to TOML")
            }
            SettingsFormat::Json => serde_json::to_string_pretty(settings)
                .context("Failed to serialize settings to JSON"),
        }
    }

    /// Parse settings from a string in the specified format.
    pub fn parse_from_str(content: &str, format: SettingsFormat) -> Result<Settings> {
        match format {
            SettingsFormat::Toml => {
                toml::from_str(content).context("Failed to parse TOML settings")
            }
            SettingsFormat::Json => {
                serde_json::from_str(content).context("Failed to parse JSON settings")
            }
        }
    }

    // ── CLI overrides ────────────────────────────────────────────────

    /// Merge with CLI arguments (CLI takes precedence).
    ///
    /// # Arguments
    ///
    /// * `model` — CLI-specified model override
    /// * `provider` — CLI-specified provider override
    /// * `enable_routing` — CLI-specified enable_routing override
    /// * `prefer_cost_efficient` — CLI-specified prefer_cost_efficient override
    /// * `fallback_chain` — CLI-specified fallback chain override
    /// * `disable_fallback` — CLI-specified disable_fallback override
    pub fn merge_cli(
        &mut self,
        model: Option<String>,
        provider: Option<String>,
        enable_routing: Option<bool>,
        prefer_cost_efficient: Option<bool>,
        fallback_chain: Option<Vec<String>>,
        disable_fallback: Option<bool>,
    ) {
        if let Some(m) = model {
            self.last_used_model = Some(m);
        }
        if let Some(p) = provider {
            self.last_used_provider = Some(p);
        }
        if let Some(r) = enable_routing {
            self.enable_routing = r;
        }
        if let Some(p) = prefer_cost_efficient {
            self.prefer_cost_efficient = p;
        }
        if let Some(fc) = fallback_chain
            && !fc.is_empty()
        {
            self.fallback_chain = fc;
        }
        if let Some(df) = disable_fallback {
            self.disable_fallback = df;
            // If disable_fallback is true, disable fallback
            if df {
                self.enable_fallback = false;
            }
        }
    }

    /// Get the effective model ID (provider/model format).
    /// Returns None if no model is configured.
    pub fn effective_model(&self, cli_model: Option<&str>) -> Option<String> {
        cli_model.map(String::from).or_else(|| {
            // Reconstruct full model ID from separate fields.
            // Handles both cases:
            //   - last_used_model = "anthropic/claude-sonnet-4" (full ID, stored by save_last_used)
            //   - last_used_model = "claude-sonnet-4" + last_used_provider = "anthropic" (split)
            let model = self.last_used_model.as_ref()?;
            if model.contains('/') {
                // Already a full model ID
                Some(model.clone())
            } else if let Some(ref provider) = self.last_used_provider {
                // Reconstruct from separate fields
                Some(format!("{}/{}", provider, model))
            } else {
                Some(model.clone())
            }
        })
    }

    /// Get the effective provider.
    /// Returns None if no provider is configured.
    pub fn effective_provider(&self, cli_provider: Option<&str>) -> Option<String> {
        cli_provider
            .map(String::from)
            .or_else(|| self.last_used_provider.clone())
    }

    /// Get the effective temperature, preferring `default_temperature` (f64)
    /// over `temperature` (f32), falling back to `None`.
    pub fn effective_temperature(&self) -> Option<f64> {
        self.default_temperature
            .or(self.temperature.map(|t| t as f64))
    }

    /// Get the effective max tokens, preferring `max_response_tokens` (usize)
    /// over `max_tokens` (u32), falling back to `None`.
    pub fn effective_max_tokens(&self) -> Option<usize> {
        self.max_response_tokens
            .or(self.max_tokens.map(|t| t as usize))
    }

    /// Get the configured router profile name.
    pub fn router_profile(&self) -> Option<&str> {
        self.router_profile.as_deref()
    }

    // ── Theme persistence ─────────────────────────────────────────────

    /// Save the last used model/provider and persist to disk.
    ///
    /// Splits the model_id on first `/` to store provider and model separately.
    pub fn save_last_used(model_id: &str) {
        if let Ok(mut settings) = Self::load() {
            if let Some((provider, model)) = model_id.split_once('/') {
                settings.last_used_provider = Some(provider.to_string());
                settings.last_used_model = Some(model.to_string());
            } else {
                settings.last_used_model = Some(model_id.to_string());
            }
            let _ = settings.save();
        }
    }

    /// Save the current theme to settings and persist to disk.
    pub fn save_theme(&mut self, name: &str) -> Result<()> {
        self.theme = name.to_string();
        self.save()
    }

    /// Get the theme name from settings, returning a default if not set.
    pub fn get_theme_name(&self) -> String {
        if self.theme.is_empty() || self.theme == "default" {
            "oxi_dark".to_string()
        } else {
            self.theme.clone()
        }
    }

    // ── Migration ────────────────────────────────────────────────────

    /// Migrate settings from an older format version to the current one.
    ///
    /// Currently handles:
    /// - Version 0 → Version 6 (multi-step)
    /// - Version 1 → Version 6 (multi-step)
    /// - Version 2 → Version 6 (multi-step)
    /// - Version 3 → Version 4 (default_model → last_used_model)
    /// - Version 4 → Version 5 (output_languages field added — no
    ///   value migration, serde default fills with empty map)
    /// - Version 5 → Version 6 (language_policy_enabled field added —
    ///   defaults to false via `#[serde(default = "default_false")]`)
    fn migrate(settings: Settings) -> Result<Settings> {
        let mut settings = settings;

        match settings.version {
            SETTINGS_VERSION => {
                // Already current — nothing to do.
            }
            0 => {
                // Version 0 = pre-versioning config.
                // Add any defaults that were introduced in version 1.
                if settings.tool_timeout_seconds == 0 {
                    settings.tool_timeout_seconds = default_tool_timeout();
                }
                settings.version = SETTINGS_VERSION;

                tracing::info!("Migrated settings from version 0 to {}", SETTINGS_VERSION);
            }
            1 | 2 => {
                // Version 1/2 → 6: dynamic_models field added + model/provider split.
                // The v3 → v4 default_model → last_used_model split doesn't apply
                // here (no default_model in v1/v2). `#[serde(default)]` fills
                // output_languages (empty) and language_policy_enabled (false).
                settings.version = SETTINGS_VERSION;
                tracing::info!(
                    "Migrated settings from version {} to {} (dynamic_models + output_languages + language_policy_enabled defaults applied)",
                    settings.version,
                    SETTINGS_VERSION
                );
            }
            3 => {
                // Version 3 → 4 step happens inline: migrate default_model → last_used_model.
                if let Some(model) = settings.default_model.take() {
                    if let Some((provider, model_name)) = model.split_once('/') {
                        settings.last_used_provider = Some(provider.to_string());
                        settings.last_used_model = Some(model_name.to_string());
                    } else {
                        settings.last_used_model = Some(model);
                    }
                }
                // Then collapse to v6: output_languages + language_policy_enabled default.
                settings.version = SETTINGS_VERSION;
                tracing::info!(
                    "Migrated settings from version 3 to {} (default_model → last_used_model; output_languages + language_policy_enabled defaults)",
                    SETTINGS_VERSION
                );
            }
            4 => {
                // Version 4 → 5 (output_languages field added) collapses to v6.
                // No value migration needed — `#[serde(default)]` fills the
                // missing fields with empty map + language_policy_enabled = false.
                settings.version = SETTINGS_VERSION;
                tracing::info!(
                    "Migrated settings from version 4 to {} (added output_languages + language_policy_enabled, both defaulted to off)",
                    SETTINGS_VERSION
                );
            }
            5 => {
                // Version 5 → 6: language_policy_enabled field added.
                // `#[serde(default = "default_false")]` fills with false (opt-in).
                // Existing v5 users with output_languages configured will see
                // their channel mappings preserved but disabled until they
                // toggle the master switch ON in /settings.
                settings.version = SETTINGS_VERSION;
                tracing::info!(
                    "Migrated settings from version 5 to {} (added language_policy_enabled, defaulting to OFF — toggle ON in /settings to activate existing channels)",
                    SETTINGS_VERSION
                );
            }
            v if v > SETTINGS_VERSION => {
                // Future version — we don't know how to downgrade.
                anyhow::bail!(
                    "Settings version {} is newer than supported version {}. \
                     Please update oxi.",
                    v,
                    SETTINGS_VERSION
                );
            }
            v => {
                // Unknown old version — best-effort migration.
                tracing::warn!(
                    "Unknown settings version {}, attempting migration to {}",
                    v,
                    SETTINGS_VERSION
                );
                settings.version = SETTINGS_VERSION;
            }
        }

        Ok(settings)
    }
}

// ── Settings format detection ──────────────────────────────────────

/// Supported settings file formats.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub enum SettingsFormat {
    /// JSON format.
    #[default]
    Json,
    /// TOML format.
    Toml,
}

impl SettingsFormat {
    /// Get the file extension for this format.
    pub fn extension(&self) -> &'static str {
        match self {
            SettingsFormat::Json => "json",
            SettingsFormat::Toml => "toml",
        }
    }
}

// ── JSON/TOML conversion helpers ────────────────────────────────────

/// Convert a TOML Value to a serde_json::Value.
fn toml_value_to_json(toml: toml::Value) -> serde_json::Value {
    match toml {
        toml::Value::String(s) => serde_json::Value::String(s),
        toml::Value::Integer(i) => serde_json::Value::Number(i.into()),
        toml::Value::Float(f) => serde_json::Number::from_f64(f)
            .map(serde_json::Value::Number)
            .unwrap_or(serde_json::Value::Null),
        toml::Value::Boolean(b) => serde_json::Value::Bool(b),
        toml::Value::Datetime(dt) => serde_json::Value::String(dt.to_string()),
        toml::Value::Array(arr) => {
            serde_json::Value::Array(arr.into_iter().map(toml_value_to_json).collect())
        }
        toml::Value::Table(table) => {
            let obj = table
                .into_iter()
                .map(|(k, v)| (k, toml_value_to_json(v)))
                .collect();
            serde_json::Value::Object(obj)
        }
    }
}

/// Deep merge two JSON values. The second value overrides the first.
fn merge_json_values(base: serde_json::Value, override_: serde_json::Value) -> serde_json::Value {
    match (base, override_) {
        // If either is not an object, the override wins
        (serde_json::Value::Object(base_map), serde_json::Value::Object(override_map)) => {
            let mut result = base_map;
            for (key, override_value) in override_map {
                let base_value = result.remove(&key);
                let merged = match base_value {
                    Some(base_v) => merge_json_values(base_v, override_value),
                    None => override_value,
                };
                result.insert(key, merged);
            }
            serde_json::Value::Object(result)
        }
        // Override wins for non-objects
        (_, override_) => override_,
    }
}

/// Parse a thinking level from a string.
pub fn parse_thinking_level(s: &str) -> Option<ThinkingLevel> {
    match s.to_lowercase().as_str() {
        "off" | "none" => Some(ThinkingLevel::Off),
        "minimal" => Some(ThinkingLevel::Minimal),
        "low" => Some(ThinkingLevel::Low),
        "medium" | "standard" => Some(ThinkingLevel::Medium),
        "high" | "thorough" => Some(ThinkingLevel::High),
        "xhigh" => Some(ThinkingLevel::XHigh),
        _ => None,
    }
}

/// Parse a boolean-like string (`"true"`, `"false"`, `"1"`, `"0"`, `"yes"`, `"no"`).
#[allow(dead_code)]
fn parse_boolish(s: &str) -> Result<bool> {
    match s.to_lowercase().as_str() {
        "true" | "1" | "yes" | "on" => Ok(true),
        "false" | "0" | "no" | "off" => Ok(false),
        _ => anyhow::bail!("Cannot parse '{}' as boolean", s),
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::io::Write as IoWrite;
    use std::sync::Mutex;

    /// Global lock to serialize all tests that manipulate process-wide env vars.
    #[allow(dead_code)] // held implicitly via guard pattern; not all tests acquire it
    static ENV_LOCK: Mutex<()> = Mutex::new(());

    /// RAII guard that removes listed env vars on creation and restores them on drop.
    /// This prevents parallel test races where one test sets an env var that leaks into another.
    struct EnvGuard {
        saved: Vec<(String, Option<String>)>,
    }

    impl EnvGuard {
        fn new(vars: &[&str]) -> Self {
            let saved = vars
                .iter()
                .map(|&name| {
                    let old = env::var(name).ok();
                    // SAFETY: test-only; the ENV_LOCK mutex serializes access.
                    unsafe { env::remove_var(name) };
                    (name.to_string(), old)
                })
                .collect();
            Self { saved }
        }
    }

    impl Drop for EnvGuard {
        fn drop(&mut self) {
            for (name, old) in self.saved.drain(..) {
                match old {
                    // SAFETY: test-only; the ENV_LOCK mutex serializes access.
                    Some(val) => unsafe { env::set_var(&name, val) },
                    None => unsafe { env::remove_var(&name) },
                }
            }
        }
    }

    // ── Struct tests ─────────────────────────────────────────────────

    #[test]
    fn test_default_settings() {
        let settings = Settings::default();
        assert_eq!(settings.version, SETTINGS_VERSION);
        assert_eq!(settings.thinking_level, ThinkingLevel::Medium);
        assert_eq!(settings.theme, "default");
        assert!(settings.last_used_model.is_none());
        assert!(settings.last_used_provider.is_none());
        assert!(settings.extensions_enabled);
        assert!(settings.auto_compaction);
        assert_eq!(settings.tool_timeout_seconds, 120);
        assert!(settings.stream_responses);
    }

    #[test]
    fn test_merge_cli() {
        let mut settings = Settings::default();
        settings.last_used_model = Some("gpt-4o".to_string());

        settings.merge_cli(Some("claude".to_string()), None, None, None, None, None);
        assert_eq!(settings.last_used_model, Some("claude".to_string()));

        settings.merge_cli(None, Some("google".to_string()), None, None, None, None);
        assert_eq!(settings.last_used_provider, Some("google".to_string()));

        // Test routing flags
        settings.merge_cli(
            None,
            None,
            Some(true),
            Some(false),
            Some(vec!["openai/gpt-4o".to_string()]),
            Some(false),
        );
        assert!(settings.enable_routing);
        assert!(!settings.prefer_cost_efficient);
        assert_eq!(settings.fallback_chain, vec!["openai/gpt-4o"]);
        assert!(!settings.disable_fallback);

        // Test disable_fallback sets enable_fallback to false
        let mut settings2 = Settings::default();
        settings2.merge_cli(None, None, None, None, None, Some(true));
        assert!(settings2.disable_fallback);
        assert!(!settings2.enable_fallback);
    }

    // ── Layered loading ──────────────────────────────────────────────

    #[test]
    fn test_layer_file_overrides() {
        let base = Settings::default();

        let tmp = tempfile::NamedTempFile::with_suffix(".toml").unwrap();
        let toml_content = r#"
last_used_model = "openai/gpt-4o"
theme = "dracula"
"#;
        tmp.as_file().write_all(toml_content.as_bytes()).unwrap();

        let merged = Settings::layer_file(&base, tmp.path()).unwrap();
        assert_eq!(merged.last_used_model, Some("openai/gpt-4o".to_string()));
        assert_eq!(merged.theme, "dracula");
        // Unchanged fields retain defaults
        assert_eq!(merged.thinking_level, ThinkingLevel::Medium);
        assert!(merged.extensions_enabled);
    }

    #[test]
    fn test_layer_file_preserves_unset() {
        let mut base = Settings::default();
        base.last_used_provider = Some("deepseek".to_string());

        let tmp = tempfile::NamedTempFile::with_suffix(".toml").unwrap();
        // Only override theme — provider should remain
        let toml_content = "theme = \"monokai\"\n";
        tmp.as_file().write_all(toml_content.as_bytes()).unwrap();

        let merged = Settings::layer_file(&base, tmp.path()).unwrap();
        assert_eq!(merged.theme, "monokai");
        assert_eq!(merged.last_used_provider, Some("deepseek".to_string()));
    }

    #[test]
    fn test_load_from_dir_with_project_config() {
        let _guard = EnvGuard::new(&[
            "OXI_MODEL",
            "OXI_PROVIDER",
            "OXI_THEME",
            "OXI_TOOL_TIMEOUT",
            "OXI_TEMPERATURE",
            "OXI_MAX_TOKENS",
            "OXI_SESSION_DIR",
            "OXI_STREAM",
            "OXI_EXTENSIONS_ENABLED",
        ]);
        let tmp = tempfile::tempdir().unwrap();
        let oxi_dir = tmp.path().join(".oxi");
        fs::create_dir_all(&oxi_dir).unwrap();
        let settings_path = oxi_dir.join("settings.toml");
        // Write v3 format: default_model contains "provider/model"
        fs::write(
            &settings_path,
            "version = 3\ndefault_model = \"google/gemini-2.0-flash\"\n",
        )
        .unwrap();

        let settings = Settings::load_from(tmp.path()).unwrap();
        // Migration moves default_model → last_used_model
        assert_eq!(
            settings.last_used_model,
            Some("gemini-2.0-flash".to_string())
        );
        assert_eq!(settings.last_used_provider, Some("google".to_string()));
    }

    #[test]
    fn test_load_from_dir_no_config() {
        // Clean env vars that load_from() reads via apply_env()
        let _guard = EnvGuard::new(&[
            "OXI_MODEL",
            "OXI_PROVIDER",
            "OXI_THEME",
            "OXI_TOOL_TIMEOUT",
            "OXI_TEMPERATURE",
            "OXI_MAX_TOKENS",
            "OXI_SESSION_DIR",
            "OXI_STREAM",
            "OXI_EXTENSIONS_ENABLED",
        ]);
        let tmp = tempfile::tempdir().unwrap();
        let settings = Settings::load_from(tmp.path()).unwrap();
        // Falls back to defaults (may include global ~/.oxi/settings)
        assert_eq!(settings.thinking_level, ThinkingLevel::Medium);
    }

    // ── Environment variables ────────────────────────────────────────

    #[test]
    fn test_from_env() {
        // NOTE: Environment variable overrides are disabled.
        // from_env() returns defaults only.
        let _guard = EnvGuard::new(&[
            // no env vars to clear
            "OXI_MODEL",
            "OXI_THEME",
            "OXI_TOOL_TIMEOUT",
            "OXI_PROVIDER",
            "OXI_DEFAULT_MODEL",
        ]);

        let settings = Settings::from_env();
        // All fields should be at defaults since env overrides are disabled
        assert_eq!(settings.last_used_model, None);
        assert_eq!(settings.theme, "default");
        assert_eq!(settings.tool_timeout_seconds, 120);
    }

    #[test]
    fn test_apply_env_boolish() {
        // NOTE: Environment variable overrides are disabled.
        // apply_env() is a no-op.
        let _guard = EnvGuard::new(&["OXI_STREAM", "OXI_EXTENSIONS_ENABLED"]);
        unsafe { env::set_var("OXI_STREAM", "false") };
        unsafe { env::set_var("OXI_EXTENSIONS_ENABLED", "0") };

        let mut settings = Settings::default();
        settings.apply_env();
        // Since env overrides are disabled, values stay at defaults
        assert!(settings.stream_responses); // default is true
        assert!(settings.extensions_enabled); // default is true
    }

    #[test]
    fn test_apply_env_temperature() {
        // NOTE: Environment variable overrides are disabled.
        let _guard = EnvGuard::new(&["OXI_TEMPERATURE"]);
        unsafe { env::set_var("OXI_TEMPERATURE", "0.7") };

        let mut settings = Settings::default();
        settings.apply_env();
        // Since env overrides are disabled, temperature stays at None
        assert_eq!(settings.default_temperature, None);
    }

    #[test]
    fn test_env_does_not_override_when_unset() {
        let _guard = EnvGuard::new(&["OXI_MODEL", "OXI_PROVIDER", "OXI_THEME", "OXI_TEMPERATURE"]);
        let settings = Settings::from_env();
        assert!(settings.last_used_model.is_none());
        assert!(settings.last_used_provider.is_none());
    }

    #[test]
    fn test_parse_thinking_level() {
        assert_eq!(parse_thinking_level("off"), Some(ThinkingLevel::Off));
        assert_eq!(parse_thinking_level("none"), Some(ThinkingLevel::Off));
        assert_eq!(
            parse_thinking_level("MINIMAL"),
            Some(ThinkingLevel::Minimal)
        );
        assert_eq!(parse_thinking_level("Low"), Some(ThinkingLevel::Low));
        assert_eq!(parse_thinking_level("medium"), Some(ThinkingLevel::Medium));
        assert_eq!(parse_thinking_level("Medium"), Some(ThinkingLevel::Medium));
        assert_eq!(
            parse_thinking_level("Standard"),
            Some(ThinkingLevel::Medium)
        );
        assert_eq!(parse_thinking_level("High"), Some(ThinkingLevel::High));
        assert_eq!(parse_thinking_level("thorough"), Some(ThinkingLevel::High));
        assert_eq!(parse_thinking_level("xhigh"), Some(ThinkingLevel::XHigh));
        assert_eq!(parse_thinking_level("invalid"), None);
    }

    #[test]
    fn test_parse_boolish() {
        assert!(parse_boolish("true").unwrap());
        assert!(parse_boolish("1").unwrap());
        assert!(parse_boolish("yes").unwrap());
        assert!(parse_boolish("ON").unwrap());
        assert!(!parse_boolish("false").unwrap());
        assert!(!parse_boolish("0").unwrap());
        assert!(!parse_boolish("no").unwrap());
        assert!(!parse_boolish("OFF").unwrap());
        assert!(parse_boolish("maybe").is_err());
    }

    // ── Effective accessors ──────────────────────────────────────────

    #[test]
    fn test_effective_model_returns_last_used() {
        let mut settings = Settings::default();
        settings.last_used_model = Some("openai/gpt-4o".to_string());
        assert_eq!(
            settings.effective_model(None),
            Some("openai/gpt-4o".to_string())
        );
    }

    #[test]
    fn test_effective_model_cli_overrides() {
        let mut settings = Settings::default();
        settings.last_used_model = Some("openai/gpt-4o".to_string());
        assert_eq!(
            settings.effective_model(Some("anthropic/claude-3")),
            Some("anthropic/claude-3".to_string())
        );
    }

    #[test]
    fn test_effective_model_none_when_unset() {
        let settings = Settings::default();
        assert_eq!(settings.effective_model(None), None);
    }

    #[test]
    fn test_effective_model_falls_back_to_last_used() {
        let mut settings = Settings::default();
        settings.last_used_model = Some("anthropic/claude-3".to_string());
        assert_eq!(
            settings.effective_model(None),
            Some("anthropic/claude-3".to_string())
        );
    }

    #[test]
    fn test_effective_model_returns_none_when_nothing_set() {
        let settings = Settings::default();
        assert_eq!(settings.effective_model(None), None);
    }

    #[test]
    fn test_effective_temperature_prefers_f64() {
        let mut settings = Settings::default();
        settings.temperature = Some(0.5);
        settings.default_temperature = Some(0.7);
        assert_eq!(settings.effective_temperature(), Some(0.7));
    }

    #[test]
    fn test_effective_temperature_falls_back_to_f32() {
        let mut settings = Settings::default();
        settings.temperature = Some(0.5);
        assert_eq!(settings.effective_temperature(), Some(0.5));
    }

    #[test]
    fn test_effective_max_tokens_prefers_usize() {
        let mut settings = Settings::default();
        settings.max_tokens = Some(1024);
        settings.max_response_tokens = Some(4096);
        assert_eq!(settings.effective_max_tokens(), Some(4096));
    }

    #[test]
    fn test_effective_max_tokens_falls_back_to_u32() {
        let mut settings = Settings::default();
        settings.max_tokens = Some(1024);
        assert_eq!(settings.effective_max_tokens(), Some(1024));
    }

    // ── Session dir ──────────────────────────────────────────────────

    #[test]
    fn test_effective_session_dir_default() {
        let _guard = EnvGuard::new(&["OXI_SESSION_DIR"]);
        let settings = Settings::default();
        let dir = settings.effective_session_dir().unwrap();
        assert!(dir.ends_with("sessions"), "dir was: {:?}", dir);
    }

    #[test]
    fn test_effective_session_dir_from_field() {
        let _guard = EnvGuard::new(&["OXI_SESSION_DIR"]);
        let mut settings = Settings::default();
        settings.session_dir = Some(PathBuf::from("/tmp/oxi-sessions"));
        assert_eq!(
            settings.effective_session_dir().unwrap(),
            PathBuf::from("/tmp/oxi-sessions")
        );
    }

    #[test]
    fn test_effective_session_dir_env_disabled() {
        // NOTE: Environment variable overrides are disabled.
        // OXI_SESSION_DIR is ignored; effective_session_dir() returns the field value (or default).
        let _guard = EnvGuard::new(&["OXI_SESSION_DIR"]);
        unsafe { env::set_var("OXI_SESSION_DIR", "/tmp/env-sessions") };
        let settings = Settings::default();
        // Env is ignored, so it should use the default path, not /tmp/env-sessions
        let dir = settings.effective_session_dir().unwrap();
        assert!(
            dir.ends_with("sessions"),
            "expected default sessions dir, got: {:?}",
            dir
        );
    }

    // ── Migration ────────────────────────────────────────────────────

    #[test]
    fn test_migration_v0_to_v1() {
        let mut settings = Settings::default();
        settings.version = 0;
        settings.tool_timeout_seconds = 0; // v0 might not have this field

        let migrated = Settings::migrate(settings).unwrap();
        assert_eq!(migrated.version, SETTINGS_VERSION);
        assert_eq!(migrated.tool_timeout_seconds, 120);
    }

    #[test]
    fn test_migration_already_current() {
        let settings = Settings::default();
        let migrated = Settings::migrate(settings).unwrap();
        assert_eq!(migrated.version, SETTINGS_VERSION);
    }

    #[test]
    fn test_migration_v3_to_v4_splits_model() {
        let mut settings = Settings::default();
        settings.version = 3;
        settings.default_model = Some("openai/gpt-4o".to_string());
        settings.default_provider = None;

        let migrated = Settings::migrate(settings).unwrap();
        assert_eq!(migrated.version, SETTINGS_VERSION);
        assert_eq!(migrated.last_used_model, Some("gpt-4o".to_string()));
        assert_eq!(migrated.last_used_provider, Some("openai".to_string()));
    }

    #[test]
    fn test_migration_v3_no_slash_keeps_model() {
        let mut settings = Settings::default();
        settings.version = 3;
        settings.default_model = Some("bare-model-name".to_string());

        let migrated = Settings::migrate(settings).unwrap();
        assert_eq!(migrated.version, SETTINGS_VERSION);
        assert_eq!(
            migrated.last_used_model,
            Some("bare-model-name".to_string())
        );
    }

    #[test]
    fn test_migration_future_version_fails() {
        let mut settings = Settings::default();
        settings.version = 9999;
        assert!(Settings::migrate(settings).is_err());
    }

    // ── output_languages tests (TUI language policy, v5) ────────────

    #[test]
    fn test_default_output_languages_is_empty() {
        let settings = Settings::default();
        assert!(
            settings.output_languages.is_empty(),
            "all channels should default to auto (empty map)"
        );
    }

    #[test]
    fn test_migration_v4_to_v5_preserves_existing_output_languages() {
        let mut settings = Settings::default();
        settings.version = 4;
        settings
            .output_languages
            .insert("response".to_string(), "ko".to_string());
        settings
            .output_languages
            .insert("commit_message".to_string(), "en".to_string());

        let migrated = Settings::migrate(settings).unwrap();
        assert_eq!(migrated.version, SETTINGS_VERSION);
        assert_eq!(
            migrated.output_languages.get("response"),
            Some(&"ko".to_string())
        );
        assert_eq!(
            migrated.output_languages.get("commit_message"),
            Some(&"en".to_string())
        );
    }

    #[test]
    fn test_migration_v4_to_v5_creates_empty_if_missing() {
        // A v4 file loaded fresh will not have `output_languages` at all —
        // serde fills it with an empty HashMap via `#[serde(default)]`.
        // After migration, version is bumped to 5 with the empty map intact.
        let mut settings = Settings::default();
        settings.version = 4;
        assert!(settings.output_languages.is_empty());

        let migrated = Settings::migrate(settings).unwrap();
        assert_eq!(migrated.version, SETTINGS_VERSION);
        assert!(migrated.output_languages.is_empty());
    }

    #[test]
    fn test_validate_keeps_user_defined_channel() {
        // Per the extension-map contract, ANY channel key must be
        // accepted (known or user-defined). The validator must NOT
        // drop unknown channels — `language_directive` will use the
        // raw key as a label fallback.
        let mut settings = Settings::default();
        settings
            .output_languages
            .insert("pr_description".to_string(), "en".to_string()); // user-defined
        settings
            .output_languages
            .insert("response".to_string(), "ko".to_string()); // known

        settings.validate_output_languages();

        assert!(settings.output_languages.contains_key("pr_description"));
        assert!(settings.output_languages.contains_key("response"));
        assert_eq!(
            settings.output_languages.get("pr_description"),
            Some(&"en".to_string())
        );
        assert_eq!(
            settings.output_languages.get("response"),
            Some(&"ko".to_string())
        );
    }

    #[test]
    fn test_validate_keeps_unknown_lang_with_warning() {
        let mut settings = Settings::default();
        settings
            .output_languages
            .insert("response".to_string(), "klingon".to_string()); // unknown code
        settings
            .output_languages
            .insert("commit_message".to_string(), "en".to_string()); // known

        settings.validate_output_languages();

        // Unknown code is KEPT (with a warn log) so users can add languages
        // without code changes.
        assert_eq!(
            settings.output_languages.get("response"),
            Some(&"klingon".to_string())
        );
        assert_eq!(
            settings.output_languages.get("commit_message"),
            Some(&"en".to_string())
        );
    }

    #[test]
    fn test_known_channels_table_includes_core_four() {
        let keys: Vec<&str> = KNOWN_CHANNELS.iter().map(|(k, _)| *k).collect();
        assert!(keys.contains(&"response"));
        assert!(keys.contains(&"code_comment"));
        assert!(keys.contains(&"documentation"));
        assert!(keys.contains(&"commit_message"));
    }

    #[test]
    fn test_known_langs_table_includes_auto_and_english() {
        let codes: Vec<&str> = KNOWN_LANGS.iter().map(|(k, _)| *k).collect();
        assert!(codes.contains(&"auto"));
        assert!(codes.contains(&"en"));
    }

    #[test]
    fn test_default_language_policy_enabled_is_false() {
        // v6: master toggle defaults to OFF (opt-in).
        let settings = Settings::default();
        assert!(
            !settings.language_policy_enabled,
            "language_policy_enabled must default to false (opt-in)"
        );
    }

    #[test]
    fn test_migration_v5_to_v6_defaults_master_toggle_to_off() {
        // v5 settings (with output_languages configured) should migrate to v6
        // with language_policy_enabled = false. Channel mappings are preserved
        // but disabled until the user flips the master switch.
        let mut settings = Settings::default();
        settings.version = 5;
        settings
            .output_languages
            .insert("response".to_string(), "ko".to_string());
        settings
            .output_languages
            .insert("commit_message".to_string(), "en".to_string());

        let migrated = Settings::migrate(settings).unwrap();
        assert_eq!(migrated.version, SETTINGS_VERSION);
        assert!(
            !migrated.language_policy_enabled,
            "v5 → v6 migration must default language_policy_enabled to false"
        );
        // Channel mappings are preserved verbatim.
        assert_eq!(
            migrated.output_languages.get("response"),
            Some(&"ko".to_string())
        );
        assert_eq!(
            migrated.output_languages.get("commit_message"),
            Some(&"en".to_string())
        );
    }

    #[test]
    fn test_save_and_load_roundtrip_preserves_language_policy_enabled() {
        let tmp = tempfile::tempdir().unwrap();
        let settings_path = tmp.path().join("settings.toml");

        let mut original = Settings::default();
        original.language_policy_enabled = true;
        original
            .output_languages
            .insert("response".to_string(), "ko".to_string());

        let content = toml::to_string_pretty(&original).unwrap();
        fs::write(&settings_path, &content).unwrap();

        let loaded_content = fs::read_to_string(&settings_path).unwrap();
        let loaded: Settings = toml::from_str(&loaded_content).unwrap();

        assert!(loaded.language_policy_enabled);
        assert_eq!(
            loaded.output_languages.get("response"),
            Some(&"ko".to_string())
        );
    }

    #[test]
    fn test_save_and_load_roundtrip_preserves_output_languages() {
        let tmp = tempfile::tempdir().unwrap();
        let settings_path = tmp.path().join("settings.toml");

        let mut original = Settings::default();
        original
            .output_languages
            .insert("response".to_string(), "ko".to_string());
        original
            .output_languages
            .insert("commit_message".to_string(), "en".to_string());

        let content = toml::to_string_pretty(&original).unwrap();
        fs::write(&settings_path, &content).unwrap();

        let loaded_content = fs::read_to_string(&settings_path).unwrap();
        let loaded: Settings = toml::from_str(&loaded_content).unwrap();

        assert_eq!(
            loaded.output_languages.get("response"),
            Some(&"ko".to_string())
        );
        assert_eq!(
            loaded.output_languages.get("commit_message"),
            Some(&"en".to_string())
        );
    }

    // ── Persistence ──────────────────────────────────────────────────

    #[test]
    fn test_save_and_load_roundtrip() {
        let tmp = tempfile::tempdir().unwrap();
        let settings_path = tmp.path().join("settings.toml");

        let mut original = Settings::default();
        original.last_used_model = Some("gpt-4o".to_string());
        original.last_used_provider = Some("openai".to_string());
        original.theme = "dracula".to_string();
        original.tool_timeout_seconds = 60;

        // Serialize
        let content = toml::to_string_pretty(&original).unwrap();
        fs::write(&settings_path, &content).unwrap();

        // Deserialize
        let loaded_content = fs::read_to_string(&settings_path).unwrap();
        let loaded: Settings = toml::from_str(&loaded_content).unwrap();

        assert_eq!(loaded.last_used_model, original.last_used_model);
        assert_eq!(loaded.theme, original.theme);
        assert_eq!(loaded.tool_timeout_seconds, original.tool_timeout_seconds);
    }

    #[test]
    fn test_toml_roundtrip_preserves_new_fields() {
        let mut settings = Settings::default();
        settings.default_temperature = Some(0.8);
        settings.max_response_tokens = Some(8192);
        settings.auto_compaction = false;
        settings.extensions_enabled = false;
        settings.session_dir = Some(PathBuf::from("/custom/sessions"));

        let toml_str = toml::to_string_pretty(&settings).unwrap();
        let parsed: Settings = toml::from_str(&toml_str).unwrap();

        assert_eq!(parsed.default_temperature, Some(0.8));
        assert_eq!(parsed.max_response_tokens, Some(8192));
        assert!(!parsed.auto_compaction);
        assert!(!parsed.extensions_enabled);
        assert_eq!(parsed.session_dir, Some(PathBuf::from("/custom/sessions")));
    }

    // ── JSON format tests ──────────────────────────────────────────────

    #[test]
    fn test_json_roundtrip() {
        let mut settings = Settings::default();
        settings.last_used_model = Some("gpt-4o".to_string());
        settings.last_used_provider = Some("openai".to_string());
        settings.theme = "dracula".to_string();
        settings.tool_timeout_seconds = 60;
        settings.default_temperature = Some(0.8);
        settings.max_response_tokens = Some(8192);

        let json_str = serde_json::to_string_pretty(&settings).unwrap();
        let parsed: Settings = serde_json::from_str(&json_str).unwrap();

        assert_eq!(parsed.last_used_model, settings.last_used_model);
        assert_eq!(parsed.theme, settings.theme);
        assert_eq!(parsed.tool_timeout_seconds, settings.tool_timeout_seconds);
        assert_eq!(parsed.default_temperature, settings.default_temperature);
        assert_eq!(parsed.max_response_tokens, settings.max_response_tokens);
    }

    #[test]
    fn test_json_serialize_for_format() {
        let mut settings = Settings::default();
        settings.last_used_model = Some("claude-3".to_string());
        settings.last_used_provider = Some("anthropic".to_string());
        settings.thinking_level = ThinkingLevel::Minimal;

        let json_content = Settings::serialize_for_format(&settings, SettingsFormat::Json).unwrap();
        let parsed: Settings = serde_json::from_str(&json_content).unwrap();

        assert_eq!(parsed.last_used_model, Some("claude-3".to_string()));
        assert_eq!(parsed.thinking_level, ThinkingLevel::Minimal);
    }

    #[test]
    fn test_toml_serialize_for_format() {
        let mut settings = Settings::default();
        settings.last_used_model = Some("gemini-pro".to_string());
        settings.last_used_provider = Some("google".to_string());
        settings.thinking_level = ThinkingLevel::High;

        let toml_content = Settings::serialize_for_format(&settings, SettingsFormat::Toml).unwrap();
        let parsed: Settings = toml::from_str(&toml_content).unwrap();

        assert_eq!(parsed.last_used_model, Some("gemini-pro".to_string()));
        assert_eq!(parsed.thinking_level, ThinkingLevel::High);
    }

    #[test]
    fn test_parse_from_str_json() {
        let json_content = r#"{
            "last_used_model": "gpt-4",
            "last_used_provider": "openai",
            "theme": "nord",
            "tool_timeout_seconds": 90
        }"#;

        let settings = Settings::parse_from_str(json_content, SettingsFormat::Json).unwrap();
        assert_eq!(settings.last_used_model, Some("gpt-4".to_string()));
        assert_eq!(settings.last_used_provider, Some("openai".to_string()));
        assert_eq!(settings.theme, "nord");
        assert_eq!(settings.tool_timeout_seconds, 90);
        // Unchanged fields retain defaults
        assert_eq!(settings.thinking_level, ThinkingLevel::Medium);
        assert!(settings.extensions_enabled);
    }

    #[test]
    fn test_parse_from_str_toml() {
        let toml_content = r#"
last_used_model = "claude-opus"
last_used_provider = "anthropic"
theme = "monokai"
tool_timeout_seconds = 45
"#;

        let settings = Settings::parse_from_str(toml_content, SettingsFormat::Toml).unwrap();
        assert_eq!(settings.last_used_model, Some("claude-opus".to_string()));
        assert_eq!(settings.last_used_provider, Some("anthropic".to_string()));
        assert_eq!(settings.theme, "monokai");
        assert_eq!(settings.tool_timeout_seconds, 45);
        assert_eq!(settings.thinking_level, ThinkingLevel::Medium);
    }

    #[test]
    fn test_layer_file_json() {
        let base = Settings::default();

        let tmp = tempfile::NamedTempFile::with_suffix(".json").unwrap();
        let json_content = r#"{
            "last_used_model": "gpt-4o",
            "last_used_provider": "openai",
            "theme": "dracula",
            "auto_compaction": false
        }"#;
        tmp.as_file().write_all(json_content.as_bytes()).unwrap();

        let merged = Settings::layer_file(&base, tmp.path()).unwrap();
        assert_eq!(merged.last_used_model, Some("gpt-4o".to_string()));
        assert_eq!(merged.last_used_provider, Some("openai".to_string()));
        assert_eq!(merged.theme, "dracula");
        assert!(!merged.auto_compaction);
        // Unchanged fields retain defaults
        assert_eq!(merged.thinking_level, ThinkingLevel::Medium);
        assert!(merged.extensions_enabled);
        assert_eq!(merged.tool_timeout_seconds, 120);
    }

    #[test]
    fn test_layer_file_json_preserves_unset() {
        let mut base = Settings::default();
        base.last_used_provider = Some("deepseek".to_string());

        let tmp = tempfile::NamedTempFile::with_suffix(".json").unwrap();
        let json_content = r#"{ "theme": "nord" }"#;
        tmp.as_file().write_all(json_content.as_bytes()).unwrap();

        let merged = Settings::layer_file(&base, tmp.path()).unwrap();
        assert_eq!(merged.theme, "nord");
        assert_eq!(merged.last_used_provider, Some("deepseek".to_string()));
    }

    #[test]
    fn test_save_to_json() {
        let tmp = tempfile::tempdir().unwrap();
        let settings_path = tmp.path().join("settings.json");

        let mut settings = Settings::default();
        settings.last_used_model = Some("gpt-4o".to_string());
        settings.last_used_provider = Some("openai".to_string());
        settings.theme = "dracula".to_string();
        settings.tool_timeout_seconds = 60;

        settings.save_to(&settings_path).unwrap();

        // Verify it's valid JSON
        let content = fs::read_to_string(&settings_path).unwrap();
        let parsed: Settings = serde_json::from_str(&content).unwrap();
        assert_eq!(parsed.last_used_model, Some("gpt-4o".to_string()));
        assert_eq!(parsed.theme, "dracula");
        assert_eq!(parsed.tool_timeout_seconds, 60);
    }

    #[test]
    fn test_save_to_toml() {
        let tmp = tempfile::tempdir().unwrap();
        let settings_path = tmp.path().join("settings.toml");

        let mut settings = Settings::default();
        settings.last_used_model = Some("gemini-pro".to_string());
        settings.last_used_provider = Some("google".to_string());
        settings.theme = "monokai".to_string();
        settings.tool_timeout_seconds = 90;

        settings.save_to(&settings_path).unwrap();

        // Verify it's valid TOML
        let content = fs::read_to_string(&settings_path).unwrap();
        let parsed: Settings = toml::from_str(&content).unwrap();
        assert_eq!(parsed.last_used_model, Some("gemini-pro".to_string()));
        assert_eq!(parsed.theme, "monokai");
        assert_eq!(parsed.tool_timeout_seconds, 90);
    }

    #[test]
    fn test_load_from_dir_with_json_project_config() {
        let _guard = EnvGuard::new(&[
            "OXI_MODEL",
            "OXI_PROVIDER",
            "OXI_THEME",
            "OXI_TOOL_TIMEOUT",
            "OXI_TEMPERATURE",
            "OXI_MAX_TOKENS",
            "OXI_SESSION_DIR",
            "OXI_STREAM",
            "OXI_EXTENSIONS_ENABLED",
        ]);
        let tmp = tempfile::tempdir().unwrap();
        let oxi_dir = tmp.path().join(".oxi");
        fs::create_dir_all(&oxi_dir).unwrap();
        let settings_path = oxi_dir.join("settings.json");
        // v3 format: default_model has provider/model
        let json_content = r#"{ "version": 3, "default_model": "google/gemini-2.0-flash" }"#;
        fs::write(&settings_path, json_content).unwrap();

        let settings = Settings::load_from(tmp.path()).unwrap();
        // Migration splits provider from model
        assert_eq!(
            settings.last_used_model,
            Some("gemini-2.0-flash".to_string())
        );
        assert_eq!(settings.last_used_provider, Some("google".to_string()));
    }

    #[test]
    fn test_find_project_settings_json_priority() {
        let tmp = tempfile::tempdir().unwrap();
        let oxi_dir = tmp.path().join(".oxi");
        fs::create_dir_all(&oxi_dir).unwrap();

        // Create both files
        let json_path = oxi_dir.join("settings.json");
        let toml_path = oxi_dir.join("settings.toml");
        fs::write(&json_path, r#"{ "theme": "json-theme" }"#).unwrap();
        fs::write(&toml_path, r#"theme = "toml-theme""#).unwrap();

        // JSON takes priority
        let found = Settings::find_project_settings(tmp.path());
        assert!(found.is_some());
        assert_eq!(
            found.unwrap().file_name().unwrap().to_str().unwrap(),
            "settings.json"
        );
    }

    #[test]
    fn test_find_project_settings_json_only() {
        let tmp = tempfile::tempdir().unwrap();
        let oxi_dir = tmp.path().join(".oxi");
        fs::create_dir_all(&oxi_dir).unwrap();

        let json_path = oxi_dir.join("settings.json");
        fs::write(&json_path, r#"{ "theme": "test" }"#).unwrap();

        let found = Settings::find_project_settings(tmp.path());
        assert!(found.is_some());
        assert_eq!(
            found.unwrap().file_name().unwrap().to_str().unwrap(),
            "settings.json"
        );
    }

    #[test]
    fn test_find_project_settings_toml_fallback() {
        let tmp = tempfile::tempdir().unwrap();
        let oxi_dir = tmp.path().join(".oxi");
        fs::create_dir_all(&oxi_dir).unwrap();

        let toml_path = oxi_dir.join("settings.toml");
        fs::write(&toml_path, r#"theme = "test""#).unwrap();

        let found = Settings::find_project_settings(tmp.path());
        assert!(found.is_some());
        assert_eq!(
            found.unwrap().file_name().unwrap().to_str().unwrap(),
            "settings.toml"
        );
    }

    #[test]
    fn test_detect_format() {
        let json_path = PathBuf::from("/test/settings.json");
        let toml_path = PathBuf::from("/test/settings.toml");
        let unknown_path = PathBuf::from("/test/settings");

        assert_eq!(Settings::detect_format(&json_path), SettingsFormat::Json);
        assert_eq!(Settings::detect_format(&toml_path), SettingsFormat::Toml);
        assert_eq!(Settings::detect_format(&unknown_path), SettingsFormat::Json);
        // Default
    }

    #[test]
    fn test_settings_format_extension() {
        assert_eq!(SettingsFormat::Json.extension(), "json");
        assert_eq!(SettingsFormat::Toml.extension(), "toml");
    }

    #[test]
    fn test_layer_json_over_toml() {
        // Test that when loading, JSON takes priority over TOML
        let tmp = tempfile::tempdir().unwrap();
        let oxi_dir = tmp.path().join(".oxi");
        fs::create_dir_all(&oxi_dir).unwrap();

        let json_path = oxi_dir.join("settings.json");
        let toml_path = oxi_dir.join("settings.toml");

        // JSON has model set to "json-model"
        fs::write(&json_path, r#"{ "last_used_model": "json-model" }"#).unwrap();
        // TOML has model set to "toml-model"
        fs::write(&toml_path, r#"last_used_model = "toml-model""#).unwrap();

        // JSON takes priority
        let settings = Settings::load_from(tmp.path()).unwrap();
        assert_eq!(settings.last_used_model, Some("json-model".to_string()));
    }

    #[test]
    fn test_mixed_format_loading() {
        // Test loading a TOML file through the generic layer_file
        let tmp = tempfile::NamedTempFile::with_suffix(".toml").unwrap();
        let toml_content = r#"
last_used_model = "loaded-via-toml"
theme = "loaded-theme"
stream_responses = false
"#;
        tmp.as_file().write_all(toml_content.as_bytes()).unwrap();

        let merged = Settings::layer_file(&Settings::default(), tmp.path()).unwrap();
        assert_eq!(merged.last_used_model, Some("loaded-via-toml".to_string()));
        assert_eq!(merged.theme, "loaded-theme");
        assert!(!merged.stream_responses);
    }

    #[test]
    fn test_merge_json_values() {
        let base = serde_json::json!({
            "version": 1,
            "theme": "default",
            "extensions": ["ext1"],
            "nested": {
                "a": 1,
                "b": 2
            }
        });

        let override_ = serde_json::json!({
            "version": 2,
            "theme": "dark",
            "extensions": ["ext2"],
            "nested": {
                "b": 20,
                "c": 30
            }
        });

        let merged = merge_json_values(base, override_);

        assert_eq!(merged["version"], 2);
        assert_eq!(merged["theme"], "dark");
        // Arrays are replaced, not merged
        assert_eq!(merged["extensions"], serde_json::json!(["ext2"]));
        // Nested objects are deeply merged
        assert_eq!(merged["nested"]["a"], 1);
        assert_eq!(merged["nested"]["b"], 20);
        assert_eq!(merged["nested"]["c"], 30);
    }

    #[test]
    fn test_save_project_preserves_existing_format() {
        let tmp = tempfile::tempdir().unwrap();
        let oxi_dir = tmp.path().join(".oxi");
        fs::create_dir_all(&oxi_dir).unwrap();

        // Create existing TOML file
        let toml_path = oxi_dir.join("settings.toml");
        fs::write(&toml_path, "theme = 'old-theme'").unwrap();

        let mut settings = Settings::default();
        settings.theme = "new-theme".to_string();
        settings.save_project(tmp.path()).unwrap();

        // Should still be TOML
        let content = fs::read_to_string(&toml_path).unwrap();
        assert!(content.contains("new-theme"));
        assert!(serde_json::from_str::<serde_json::Value>(&content).is_err());
    }

    #[test]
    fn test_save_project_creates_json_by_default() {
        let tmp = tempfile::tempdir().unwrap();
        let oxi_dir = tmp.path().join(".oxi");
        fs::create_dir_all(&oxi_dir).unwrap();
        // Don't create any settings file

        let mut settings = Settings::default();
        settings.theme = "json-theme".to_string();
        settings.save_project(tmp.path()).unwrap();

        // Should create JSON file
        let json_path = oxi_dir.join("settings.json");
        assert!(json_path.exists());
        let content = fs::read_to_string(&json_path).unwrap();
        assert!(serde_json::from_str::<serde_json::Value>(&content).is_ok());
        assert!(content.contains("json-theme"));
    }

    // ── Custom provider tests ───────────────────────────────────────

    #[test]
    fn test_custom_provider_default_api() {
        use super::CustomProvider;
        let cp = CustomProvider {
            name: "test".to_string(),
            base_url: "https://api.test.com/v1".to_string(),
            api_key_env: "TEST_API_KEY".to_string(),
            api: super::default_custom_provider_api(),
        };
        assert_eq!(cp.api, "openai-completions");
    }

    #[test]
    fn test_custom_provider_toml_deserialize() {
        let toml_content = r#"
[[custom_providers]]
name = "minimax"
base_url = "https://api.minimax.chat/v1"
api_key_env = "MINIMAX_API_KEY"
api = "openai-completions"

[[custom_providers]]
name = "zai"
base_url = "https://api.z.ai/v1"
api_key_env = "ZAI_API_KEY"
api = "openai-responses"
"#;
        let settings: Settings = toml::from_str(toml_content).unwrap();
        assert_eq!(settings.custom_providers.len(), 2);
        assert_eq!(settings.custom_providers[0].name, "minimax");
        assert_eq!(
            settings.custom_providers[0].base_url,
            "https://api.minimax.chat/v1"
        );
        assert_eq!(settings.custom_providers[0].api_key_env, "MINIMAX_API_KEY");
        assert_eq!(settings.custom_providers[0].api, "openai-completions");
        assert_eq!(settings.custom_providers[1].name, "zai");
        assert_eq!(settings.custom_providers[1].api, "openai-responses");
    }

    #[test]
    fn test_custom_provider_json_deserialize() {
        let json_content = r#"{
            "custom_providers": [
                {
                    "name": "minimax",
                    "base_url": "https://api.minimax.chat/v1",
                    "api_key_env": "MINIMAX_API_KEY",
                    "api": "openai-completions"
                }
            ]
        }"#;
        let settings: Settings = serde_json::from_str(json_content).unwrap();
        assert_eq!(settings.custom_providers.len(), 1);
        assert_eq!(settings.custom_providers[0].name, "minimax");
    }

    #[test]
    fn test_custom_provider_toml_roundtrip() {
        let mut settings = Settings::default();
        settings.custom_providers.push(super::CustomProvider {
            name: "test".to_string(),
            base_url: "https://api.test.com/v1".to_string(),
            api_key_env: "TEST_API_KEY".to_string(),
            api: "openai-completions".to_string(),
        });

        let toml_str = toml::to_string_pretty(&settings).unwrap();
        let parsed: Settings = toml::from_str(&toml_str).unwrap();
        assert_eq!(parsed.custom_providers.len(), 1);
        assert_eq!(parsed.custom_providers[0].name, "test");
        assert_eq!(
            parsed.custom_providers[0].base_url,
            "https://api.test.com/v1"
        );
    }

    #[test]
    fn test_custom_provider_defaults_empty() {
        let settings = Settings::default();
        assert!(settings.custom_providers.is_empty());
    }

    #[test]
    fn test_custom_provider_layer_file() {
        let base = Settings::default();

        let tmp = tempfile::NamedTempFile::with_suffix(".toml").unwrap();
        let toml_content = r#"
[[custom_providers]]
name = "my-provider"
base_url = "https://api.my-provider.com/v1"
api_key_env = "MY_PROVIDER_API_KEY"
"#;
        tmp.as_file().write_all(toml_content.as_bytes()).unwrap();

        let merged = Settings::layer_file(&base, tmp.path()).unwrap();
        assert_eq!(merged.custom_providers.len(), 1);
        assert_eq!(merged.custom_providers[0].name, "my-provider");
        // Default api value
        assert_eq!(merged.custom_providers[0].api, "openai-completions");
    }
}