a3s_code_core/

prompts.rs

// Prompt Registry
//
// Central registry for default system prompts and prompt templates used in
// A3S Code. Every LLM-facing default pack is externalized here as a
// compile-time `include_str!` so the shipping defaults are visible in one place.
//
// Ownership (`HARNESS-CONV6`):
// - Core owns AgentStyle → hard permission overlays, runtime/tool contracts,
//   and `SystemPromptSlots` assembly. Prompt text never grants a capability.
// - Specialty markdown bodies under `prompts/` are a replaceable default pack.
//   Hosts may replace role/guidelines/extra (and eventually the whole pack);
//   reviewer rubrics and product prompts remain host-owned.
//
// Directory layout:
//   prompts/
//   ├── common/   — shared runtime prompts used by multiple subsystems
//   ├── analysis/ — intent classification and pre-analysis prompts
//   ├── planning/ — planner and plan execution prompts
//   └── agents/   — built-in delegated-agent role prompts

// ============================================================================
// Default System Prompt
// ============================================================================

use crate::llm::LlmClient;
use anyhow::Context;

/// Default agentic system prompt — injected when no system prompt is configured.
///
/// Instructs the LLM to behave as an autonomous coding agent: use tools to act,
/// verify results, and keep working until the task is fully complete.
pub const SYSTEM_DEFAULT: &str = include_str!("../prompts/common/system_default.md");

/// Continuation message — injected as a user turn when the LLM stops without
/// completing the task (i.e. stops calling tools mid-task).
pub const CONTINUATION: &str = include_str!("../prompts/common/continuation.md");

/// Safety boundaries (injection hygiene, secret handling, malicious-code refusal).
///
/// Single source of truth, appended to every assembled system prompt by
/// [`SystemPromptSlots::build_with_style`] so it applies uniformly across all
/// agent styles and delegated subagents (which build through the same path).
pub const BOUNDARIES: &str = include_str!("../prompts/common/boundaries.md");

/// Canonical repository-tool arguments and context-efficient usage strategy.
///
/// Appended to writable / general styles so parameter and pagination guidance
/// stay aligned with the registered schemas.
pub const REPOSITORY_TOOL_CONTRACT: &str =
    include_str!("../prompts/common/repository_tool_contract.md");

/// Read-oriented repository-tool contract for specialty styles that must not
/// advertise mutating tools while claiming a read-only role.
pub const REPOSITORY_TOOL_CONTRACT_READONLY: &str =
    include_str!("../prompts/common/repository_tool_contract_readonly.md");

/// Shared runtime contract for authority, scope, run control, evidence, and
/// completion semantics.
///
/// This contract is appended to every assembled prompt.  It describes the
/// model-facing boundary; enforcement remains in the host runtime and tool
/// implementations.
pub const RUNTIME_CONTRACT: &str = include_str!("../prompts/common/runtime_contract.md");

// ============================================================================
// Delegated Run Prompts
// ============================================================================

/// Explore delegated run — read-only codebase exploration
pub const AGENT_EXPLORE: &str = include_str!("../prompts/agents/explore.md");

/// Plan delegated run — read-only planning and analysis
pub const AGENT_PLAN: &str = include_str!("../prompts/agents/plan.md");

/// Code review delegated run — issue finding and review focus
pub const AGENT_CODE_REVIEW: &str = include_str!("../prompts/agents/code_review.md");

// ============================================================================
// Session — Context Compaction
// ============================================================================

/// User template for context compaction. Placeholder: `{conversation}`
pub const CONTEXT_COMPACT: &str = include_str!("../prompts/common/context_compact.md");

/// Prefix for compacted summary messages
pub const CONTEXT_SUMMARY_PREFIX: &str =
    include_str!("../prompts/common/context_summary_prefix.md");

// ============================================================================
// LLM Planner — JSON-structured prompts
// ============================================================================

/// System prompt for LLM planner: plan creation (JSON output)
pub const LLM_PLAN_SYSTEM: &str = include_str!("../prompts/planning/llm_plan_system.md");

/// System prompt for LLM planner: goal extraction (JSON output)
pub const LLM_GOAL_EXTRACT_SYSTEM: &str =
    include_str!("../prompts/planning/llm_goal_extract_system.md");

/// System prompt for LLM planner: goal achievement check (JSON output)
pub const LLM_GOAL_CHECK_SYSTEM: &str =
    include_str!("../prompts/planning/llm_goal_check_system.md");

/// System prompt for pre-analysis: combined intent + goal + plan + input optimization.
pub const PRE_ANALYSIS_SYSTEM: &str = include_str!("../prompts/analysis/pre_analysis_system.md");

// ============================================================================
// Plan Execution Templates
// ============================================================================

/// Template for initial plan execution message
pub const PLAN_EXECUTE_GOAL: &str = include_str!("../prompts/planning/plan_execute_goal.md");

/// Template for per-step execution prompt
pub const PLAN_EXECUTE_STEP: &str = include_str!("../prompts/planning/plan_execute_step.md");

/// Skill catalog header injected before listing available skill names/descriptions.
pub const SKILLS_CATALOG_HEADER: &str = include_str!("../prompts/common/skills_catalog_header.md");

// ============================================================================
// Verification Agent
// ============================================================================

/// Verification agent — adversarial specialist that tries to break code
pub const AGENT_VERIFICATION: &str = include_str!("../prompts/agents/verification.md");

// ============================================================================
// Intent Classification
// ============================================================================

/// System prompt for LLM-based intent classification
pub const INTENT_CLASSIFY_SYSTEM: &str =
    include_str!("../prompts/analysis/intent_classify_system.md");

// ============================================================================
// Planning Mode (Auto-Detection)
// ============================================================================

use serde::{Deserialize, Serialize};

/// Planning mode — controls when planning phase is used.
///
/// When set to `Auto` (the default), the system detects from the user's
/// message whether planning should be enabled. When explicitly `Enabled`,
/// planning runs on every execution. When `Disabled`, planning is skipped.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default, Serialize, Deserialize)]
pub enum PlanningMode {
    /// Automatically detect from message content — enables planning when the
    /// message benefits from structured pre-analysis. Local keyword detection is
    /// only a fallback when pre-analysis is unavailable.
    #[default]
    Auto,
    /// Explicitly disabled — never use planning phase.
    Disabled,
    /// Explicitly enabled — always use planning phase.
    Enabled,
}

impl PlanningMode {
    /// Returns true for the local no-LLM fallback path.
    ///
    /// Normal agent execution runs pre-analysis in `Auto` mode and uses its
    /// structured `requires_planning` decision instead of this heuristic.
    pub fn should_plan(&self, message: &str) -> bool {
        match self {
            PlanningMode::Auto => AgentStyle::detect_from_message(message).requires_planning(),
            PlanningMode::Enabled => true,
            PlanningMode::Disabled => false,
        }
    }
}

// ============================================================================
// Agent Style (Intent-Based Prompt Selection)
// ============================================================================

/// Agent style — determines which system prompt template is used.
///
/// Each style has a different focus and behavior, selected based on the user's
/// apparent intent from their message.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub enum AgentStyle {
    /// Default — general purpose coding agent for research and multi-step tasks.
    #[default]
    GeneralPurpose,
    /// Read-only planning and architecture analysis.
    /// Prohibited from modifying files, focuses on design and planning.
    Plan,
    /// Adversarial verification specialist — tries to break code, not confirm it works.
    Verification,
    /// Fast file search and codebase exploration.
    /// Read-only, optimized for finding files and patterns quickly.
    Explore,
    /// Code review focused — analyzes code quality, best practices, potential issues.
    CodeReview,
}

/// Detection confidence level for style detection.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum DetectionConfidence {
    /// High confidence — very specific keywords, skip LLM classification.
    High,
    /// Medium confidence — some indicators present, LLM classification helpful.
    Medium,
    /// Low confidence — no clear indicators, LLM classification recommended.
    Low,
}

impl AgentStyle {
    /// Returns true if this style is a specialty read-oriented role whose
    /// prompt must not advertise workspace mutations as normal work.
    pub fn uses_readonly_tool_contract(&self) -> bool {
        matches!(
            self,
            AgentStyle::Plan
                | AgentStyle::Explore
                | AgentStyle::Verification
                | AgentStyle::CodeReview
        )
    }

    /// Repository-tool contract fragment for this style.
    pub fn repository_tool_contract(&self) -> &'static str {
        if self.uses_readonly_tool_contract() {
            REPOSITORY_TOOL_CONTRACT_READONLY
        } else {
            REPOSITORY_TOOL_CONTRACT
        }
    }

    /// Returns the base system prompt for this style.
    pub fn base_prompt(&self) -> &'static str {
        match self {
            AgentStyle::GeneralPurpose => SYSTEM_DEFAULT,
            AgentStyle::Plan => AGENT_PLAN,
            AgentStyle::Verification => AGENT_VERIFICATION,
            AgentStyle::Explore => AGENT_EXPLORE,
            AgentStyle::CodeReview => AGENT_CODE_REVIEW,
        }
    }

    /// Returns style-specific guidelines if any.
    pub fn guidelines(&self) -> Option<&'static str> {
        match self {
            AgentStyle::GeneralPurpose => None,
            AgentStyle::Plan => None, // Already embedded in agents/plan.md
            AgentStyle::Verification => None, // Already embedded in agents/verification.md
            AgentStyle::Explore => None, // Already embedded in agents/explore.md
            AgentStyle::CodeReview => None,
        }
    }

    /// Returns a one-line description of this style.
    pub fn description(&self) -> &'static str {
        match self {
            AgentStyle::GeneralPurpose => {
                "General purpose coding agent for research and multi-step tasks"
            }
            AgentStyle::Plan => "Read-only planning and architecture analysis agent",
            AgentStyle::Verification => "Adversarial verification specialist — tries to break code",
            AgentStyle::Explore => "Fast read-only file search and codebase exploration agent",
            AgentStyle::CodeReview => "Code review focused — analyzes quality and best practices",
        }
    }

    /// Returns the canonical built-in delegated-agent name for this style.
    pub fn builtin_agent_name(&self) -> &'static str {
        match self {
            AgentStyle::GeneralPurpose => "general",
            AgentStyle::Plan => "plan",
            AgentStyle::Verification => "verification",
            AgentStyle::Explore => "explore",
            AgentStyle::CodeReview => "review",
        }
    }

    /// Returns the stable runtime mode label for UI/event consumers.
    pub fn runtime_mode(&self) -> &'static str {
        match self {
            AgentStyle::GeneralPurpose => "general",
            AgentStyle::Plan => "planning",
            AgentStyle::Verification => "verification",
            AgentStyle::Explore => "explore",
            AgentStyle::CodeReview => "code_review",
        }
    }

    /// Returns true if this style benefits from a planning phase.
    ///
    /// Planning is beneficial for styles that involve multi-step execution
    /// or where a structured approach improves outcomes.
    pub fn requires_planning(&self) -> bool {
        matches!(self, AgentStyle::Plan)
    }

    /// Detects the most appropriate agent style based on user message content,
    /// along with a confidence level.
    ///
    /// This is a local fallback for environments where LLM pre-analysis is
    /// unavailable. Normal execution uses structured pre-analysis first.
    pub fn detect_with_confidence(message: &str) -> (Self, DetectionConfidence) {
        // Chinese text has high ambiguity in intent classification due to
        // compound verb structures and context-dependent meaning.
        // Bypass keyword matching entirely and route to LLM classification.
        if message
            .chars()
            .any(|c| ('\u{4e00}'..='\u{9fff}').contains(&c))
        {
            return (AgentStyle::GeneralPurpose, DetectionConfidence::Low);
        }

        let lower = message.to_lowercase();

        // === HIGH CONFIDENCE: Very specific patterns ===

        // Strong verification indicators
        if lower.contains("try to break")
            || lower.contains("find vulnerabilities")
            || lower.contains("adversarial")
            || lower.contains("security audit")
        {
            return (AgentStyle::Verification, DetectionConfidence::High);
        }

        // Strong plan indicators
        if lower.contains("help me plan")
            || lower.contains("help me design")
            || lower.contains("create a plan")
            || lower.contains("implementation plan")
            || lower.contains("step-by-step plan")
        {
            return (AgentStyle::Plan, DetectionConfidence::High);
        }

        // Strong exploration indicators
        if lower.contains("find all files")
            || lower.contains("search for all")
            || lower.contains("locate all")
        {
            return (AgentStyle::Explore, DetectionConfidence::High);
        }

        // === MEDIUM CONFIDENCE: Specific but less definitive ===

        // Verification keywords
        if lower.contains("verify")
            || lower.contains("verification")
            || lower.contains("break")
            || lower.contains("debug")
            || lower.contains("test")
            || lower.contains("check if")
        {
            return (AgentStyle::Verification, DetectionConfidence::Medium);
        }

        // Plan keywords
        if lower.contains("plan")
            || lower.contains("design")
            || lower.contains("architecture")
            || lower.contains("approach")
        {
            return (AgentStyle::Plan, DetectionConfidence::Medium);
        }

        // Explore keywords
        if lower.contains("find")
            || lower.contains("search")
            || lower.contains("where is")
            || lower.contains("where's")
            || lower.contains("locate")
            || lower.contains("explore")
            || lower.contains("look for")
        {
            return (AgentStyle::Explore, DetectionConfidence::Medium);
        }

        // Code review keywords
        if lower.contains("review")
            || lower.contains("code review")
            || lower.contains("analyze")
            || lower.contains("assess")
            || lower.contains("quality")
            || lower.contains("best practice")
        {
            return (AgentStyle::CodeReview, DetectionConfidence::Medium);
        }

        // No clear indicators
        (AgentStyle::GeneralPurpose, DetectionConfidence::Low)
    }

    /// Detects the most appropriate agent style based on user message content.
    ///
    /// This is a local fallback heuristic. Normal execution uses structured
    /// pre-analysis first; users can also explicitly set the style via
    /// `SystemPromptSlots::with_style()`.
    pub fn detect_from_message(message: &str) -> Self {
        Self::detect_with_confidence(message).0
    }

    /// Classifies user intent using LLM when keyword confidence is low.
    ///
    /// This helper is available to callers that want explicit one-shot intent
    /// classification outside the main pre-analysis path.
    ///
    /// Uses a lightweight classification prompt that returns a single word.
    pub async fn detect_with_llm(llm: &dyn LlmClient, message: &str) -> anyhow::Result<Self> {
        use crate::llm::Message;

        let system = INTENT_CLASSIFY_SYSTEM;
        let messages = vec![Message::user(message)];

        let response = llm
            .complete(&messages, Some(system), &[])
            .await
            .context("LLM intent classification failed")?;

        let text = response.text().trim().to_lowercase();

        let style = match text.as_str() {
            "plan" => AgentStyle::Plan,
            "explore" => AgentStyle::Explore,
            "verification" => AgentStyle::Verification,
            "codereview" | "code review" => AgentStyle::CodeReview,
            _ => AgentStyle::GeneralPurpose,
        };

        Ok(style)
    }
}

// ============================================================================
// System Prompt Slots
// ============================================================================

/// Slot-based system prompt customization with intent-based style selection.
///
/// Users can customize specific parts of the system prompt without overriding
/// the core agentic capabilities (tool usage, autonomous behavior, completion
/// criteria). The default agentic core is ALWAYS included.
///
/// ## Assembly Order
///
/// ```text
/// [role]            ← Custom identity/role (e.g. "You are a Python expert")
/// [CORE]            ← Always present: Core Behaviour + Tool Usage Strategy + Completion Criteria
/// [runtime]         ← Host authority, scope, run-control, evidence contract
/// [repository]      ← Canonical repository-tool schemas and usage rules
/// [boundaries]      ← Injection, secret, and malicious-code boundaries
/// [guidelines]      ← Custom coding rules / constraints
/// [response_style]  ← Custom response format (replaces default Response Format section)
/// [extra]           ← Freeform additional instructions
/// ```
///
/// Host-customizable edges around the Core default prompt pack.
///
/// The core agentic loop, runtime contract, repository-tool schema, safety
/// boundaries, and style→permission overlays always remain authoritative.
/// Specialty markdown bodies are a default pack only — not a capability source
/// and not a reviewer/rubric owner (`HARNESS-CONV6` / `PROMPT-ALIGN1`).
///
/// ## Intent-Based Selection
///
/// When `style` is left as `AgentStyle::GeneralPurpose` (the default), the
/// system will attempt to detect the user's intent from their first message and
/// automatically select an appropriate style. To override this behavior, explicitly
/// set the `style` field.
#[derive(Debug, Clone, Default)]
pub struct SystemPromptSlots {
    /// Agent style — determines which base prompt template is used.
    ///
    /// When `None` (default), the style is auto-detected from the user's message.
    /// Explicitly set this to force a particular style regardless of message content.
    pub style: Option<AgentStyle>,

    /// Custom role/identity prepended before the core prompt.
    ///
    /// Example: "You are a senior Python developer specializing in FastAPI."
    /// When set, replaces the default "You are A3S Code, an expert AI coding agent" line.
    pub role: Option<String>,

    /// Custom coding guidelines appended after the core prompt sections.
    ///
    /// Example: "Always use type hints. Follow PEP 8. Prefer dataclasses over dicts."
    pub guidelines: Option<String>,

    /// Custom response style that replaces the default "Response Format" section.
    ///
    /// When `None`, the default response format is used.
    pub response_style: Option<String>,

    /// Explicit user-facing reply language as a BCP-47 tag (for example `zh-CN`
    /// or `en-US`). When set, overrides the soft "match the user's language"
    /// default so hosts can pin replies to the product UI locale.
    pub output_language: Option<String>,

    /// Freeform extra instructions appended at the very end.
    pub extra: Option<String>,
}

/// The default role line in SYSTEM_DEFAULT that gets replaced when `role` slot is set.
const DEFAULT_ROLE_LINE: &str = include_str!("../prompts/common/system_default_role_line.md");

/// The default response format section.
const DEFAULT_RESPONSE_FORMAT: &str =
    include_str!("../prompts/common/system_default_response_format.md");

impl SystemPromptSlots {
    /// Build the final system prompt by assembling slots around the core prompt.
    ///
    /// The core agentic behavior, runtime contract, shared repository-tool
    /// contract, and safety boundaries are always preserved. Users can only
    /// customize the edges.
    ///
    /// Note: This uses `AgentStyle::GeneralPurpose` as the base. Use
    /// `build_with_message()` to enable automatic intent-based style detection.
    pub fn build(&self) -> String {
        self.build_with_style(self.style.unwrap_or_default())
    }

    /// Build the final system prompt, auto-detecting style from the initial message.
    ///
    /// If `self.style` is explicitly set, that style is used regardless of message content.
    /// Otherwise, the style is detected from `initial_message` using keyword analysis.
    pub fn build_with_message(&self, initial_message: &str) -> String {
        let style = self
            .style
            .unwrap_or_else(|| AgentStyle::detect_from_message(initial_message));
        self.build_with_style(style)
    }

    /// Build the prompt with an explicitly specified style.
    fn build_with_style(&self, style: AgentStyle) -> String {
        let mut parts: Vec<String> = Vec::new();

        // Normalize line endings: strip \r so string matching works on Windows
        // where include_str! may produce \r\n if the file has CRLF endings.
        let base_prompt = style.base_prompt().replace('\r', "");
        let default_role_line = DEFAULT_ROLE_LINE.replace('\r', "");
        let default_response_format = DEFAULT_RESPONSE_FORMAT.replace('\r', "");

        // 1. Role: for GeneralPurpose, replace the default role line.
        // For other styles (Plan, Explore, Verification), prepend custom role since
        // those prompts have their own identity embedded.
        let core = if let Some(ref role) = self.role {
            if style == AgentStyle::GeneralPurpose {
                let custom_role = format!(
                    "{} Working inside the user's workspace, use the tools exposed in the current turn to inspect, change, and verify the requested work; continue until the user's request is genuinely complete.",
                    role.trim_end_matches('.')
                );
                base_prompt.replace(&default_role_line, &custom_role)
            } else {
                // Prepend custom role for other styles
                format!("{}\n\n{}", role, base_prompt)
            }
        } else {
            base_prompt
        };

        // 2. Core: strip the default response format section if custom one is provided
        let core = if self.response_style.is_some() {
            core.replace(&default_response_format, "")
                .trim_end()
                .to_string()
        } else {
            core.trim_end().to_string()
        };

        parts.push(core);

        // 2b. Runtime contract — shared by every style so authority, run
        // control, and evidence semantics cannot drift between built-in agents.
        parts.push(RUNTIME_CONTRACT.replace('\r', "").trim_end().to_string());

        // 2c. Repository-tool contract — style-scoped so read-oriented roles do
        // not advertise mutating tools while claiming a read-only task.
        parts.push(
            style
                .repository_tool_contract()
                .replace('\r', "")
                .trim_end()
                .to_string(),
        );

        // 2d. Safety boundaries — single source of truth, appended uniformly so
        // every style and delegated subagent (which build through this path)
        // carries injection-hygiene, secret-handling, and malware-refusal rules.
        parts.push(BOUNDARIES.replace('\r', "").trim_end().to_string());

        // 2e. Explicit output language — host-pinned product language for UI
        // locales. Covers every user-visible prose surface (replies, reasoning,
        // plans). When absent, the soft "user's language" rule remains.
        if let Some(language) = self
            .output_language
            .as_deref()
            .map(str::trim)
            .filter(|value| !value.is_empty())
        {
            parts.push(output_language_contract(language));
        }

        // 3. Custom response style (replaces default Response Format)
        if let Some(ref style) = self.response_style {
            parts.push(format!("## Response Format\n\n{}", style));
        }

        // 4. Guidelines: style-specific + custom
        let style_guidelines = style.guidelines();
        if style_guidelines.is_some() || self.guidelines.is_some() {
            let mut guidelines_parts = Vec::new();
            if let Some(sg) = style_guidelines {
                guidelines_parts.push(sg.to_string());
            }
            if let Some(ref g) = self.guidelines {
                guidelines_parts.push(g.clone());
            }
            parts.push(format!(
                "## Guidelines\n\n{}",
                guidelines_parts.join("\n\n")
            ));
        }

        // 5. Extra freeform instructions.
        if let Some(ref extra) = self.extra {
            parts.push(extra.clone());
        }

        parts.join("\n\n")
    }

    /// Returns true if all slots are empty (use pure default prompt).
    pub fn is_empty(&self) -> bool {
        self.style.is_none()
            && self.role.is_none()
            && self.guidelines.is_none()
            && self.response_style.is_none()
            && self.output_language.is_none()
            && self.extra.is_none()
    }

    /// Set the agent style explicitly.
    pub fn with_style(mut self, style: AgentStyle) -> Self {
        self.style = Some(style);
        self
    }

    /// Set the role/identity.
    pub fn with_role(mut self, role: impl Into<String>) -> Self {
        self.role = Some(role.into());
        self
    }

    /// Set custom guidelines.
    pub fn with_guidelines(mut self, guidelines: impl Into<String>) -> Self {
        self.guidelines = Some(guidelines.into());
        self
    }

    /// Set custom response style.
    pub fn with_response_style(mut self, style: impl Into<String>) -> Self {
        self.response_style = Some(style.into());
        self
    }

    /// Pin user-facing replies to a BCP-47 language tag (for example `zh-CN`).
    pub fn with_output_language(mut self, language: impl Into<String>) -> Self {
        let language = language.into();
        self.output_language = (!language.trim().is_empty()).then_some(language);
        self
    }

    /// Set extra instructions.
    pub fn with_extra(mut self, extra: impl Into<String>) -> Self {
        self.extra = Some(extra.into());
        self
    }
}

/// Single product-language contract for every user-visible prose surface.
///
/// Hosts pin a BCP-47 tag once; replies, reasoning/thinking, plans, goals, and
/// step descriptions all follow it. Identifiers and quoted source stay as-is.
/// Keep this text in one place so planner prompts and the main system prompt
/// cannot drift.
pub fn output_language_contract(language: &str) -> String {
    format!(
        "## Output Language\n\n\
Write all user-visible product prose in {language}: replies, reasoning/thinking, \
plans, goals, step descriptions, and status updates. Use that one language only; \
do not mix languages across those surfaces.\n\
Keep code, identifiers, file paths, commands, URLs, and quoted source text in their original form.\n\
Do not switch languages because tool output or retrieved sources use another language."
    )
}

/// Resolve the language for planning/goal JSON prose.
///
/// Prefer an explicit host pin; otherwise infer from the user request so a
/// Chinese prompt does not yield an English plan when the host forgot to pin.
pub fn resolve_product_output_language(pinned: Option<&str>, user_text: &str) -> Option<String> {
    pinned
        .map(str::trim)
        .filter(|value| !value.is_empty())
        .map(str::to_owned)
        .or_else(|| infer_user_reply_language(user_text).map(str::to_owned))
}

/// Infer a BCP-47 reply-language tag from user-authored text.
///
/// Uses script counts only (no NLP). Returns `None` when the sample is too
/// short or script evidence is inconclusive, so hosts can keep the previous
/// pin or the soft "match the user" rule.
pub fn infer_user_reply_language(text: &str) -> Option<&'static str> {
    let mut han = 0u32;
    let mut kana = 0u32;
    let mut hangul = 0u32;
    let mut latin = 0u32;

    for ch in text.chars() {
        if ch.is_ascii_alphabetic() {
            latin = latin.saturating_add(1);
            continue;
        }
        let code = ch as u32;
        // CJK Unified Ideographs + Extension A (common Han)
        if (0x4E00..=0x9FFF).contains(&code) || (0x3400..=0x4DBF).contains(&code) {
            han = han.saturating_add(1);
        } else if (0x3040..=0x30FF).contains(&code) {
            // Hiragana + Katakana
            kana = kana.saturating_add(1);
        } else if (0xAC00..=0xD7AF).contains(&code) || (0x1100..=0x11FF).contains(&code) {
            hangul = hangul.saturating_add(1);
        }
    }

    let marked = han + kana + hangul + latin;
    if marked < 2 {
        return None;
    }

    // Prefer non-Latin scripts when the user clearly wrote in them, even if
    // English identifiers appear ("帮我 fix 这个 bug").
    if hangul >= 2 && hangul >= han && hangul >= kana {
        return Some("ko");
    }
    if kana >= 2 {
        return Some("ja");
    }
    if han >= 2 {
        return Some("zh-CN");
    }
    // Short English acknowledgements ("ok", "thanks") must not flip an
    // established reply language; require a stronger Latin sample.
    if latin >= 12 {
        return Some("en");
    }
    None
}

// ============================================================================
// Helper Functions
// ============================================================================

/// Render a template by replacing `{key}` placeholders with values
pub fn render(template: &str, vars: &[(&str, &str)]) -> String {
    let mut result = template.to_string();
    for (key, value) in vars {
        result = result.replace(&format!("{{{}}}", key), value);
    }
    result
}

#[cfg(test)]
#[path = "prompts/tests.rs"]
mod tests;