deepseek-tui 0.8.20

#![allow(clippy::items_after_test_module)]

//! Debug commands: tokens, cost, system, context, undo, retry

use std::time::Instant;

use super::CommandResult;
use crate::compaction::estimate_input_tokens_conservative;
use crate::localization::{Locale, MessageId, tr};
use crate::models::{SystemPrompt, context_window_for_model};
use crate::tui::app::{App, AppAction, TurnCacheRecord};
use crate::tui::history::HistoryCell;

fn token_count(value: Option<u32>, locale: Locale) -> String {
    value.map_or_else(
        || tr(locale, MessageId::CmdTokensNotReported).to_string(),
        |tokens| tokens.to_string(),
    )
}

fn active_context_summary(app: &App, locale: Locale) -> String {
    let estimated =
        estimate_input_tokens_conservative(&app.api_messages, app.system_prompt.as_ref());
    match context_window_for_model(&app.model) {
        Some(window) => {
            let used = estimated.min(window as usize);
            let percent = (used as f64 / f64::from(window) * 100.0).clamp(0.0, 100.0);
            tr(locale, MessageId::CmdTokensContextWithWindow)
                .replace("{used}", &used.to_string())
                .replace("{window}", &window.to_string())
                .replace("{percent}", &format!("{percent:.1}"))
        }
        None => tr(locale, MessageId::CmdTokensContextUnknownWindow)
            .replace("{estimated}", &estimated.to_string()),
    }
}

fn cache_summary(app: &App, locale: Locale) -> String {
    match (
        app.session.last_prompt_cache_hit_tokens,
        app.session.last_prompt_cache_miss_tokens,
    ) {
        (Some(hit), Some(miss)) => tr(locale, MessageId::CmdTokensCacheBoth)
            .replace("{hit}", &hit.to_string())
            .replace("{miss}", &miss.to_string()),
        (Some(hit), None) => {
            tr(locale, MessageId::CmdTokensCacheHitOnly).replace("{hit}", &hit.to_string())
        }
        (None, Some(miss)) => {
            tr(locale, MessageId::CmdTokensCacheMissOnly).replace("{miss}", &miss.to_string())
        }
        (None, None) => tr(locale, MessageId::CmdTokensNotReported).to_string(),
    }
}

/// Show token usage for session
pub fn tokens(app: &mut App) -> CommandResult {
    let locale = app.ui_locale;
    let message_count = app.api_messages.len();
    let chat_count = app.history.len();

    let report = tr(locale, MessageId::CmdTokensReport)
        .replace("{active}", &active_context_summary(app, locale))
        .replace(
            "{input}",
            &token_count(app.session.last_prompt_tokens, locale),
        )
        .replace(
            "{output}",
            &token_count(app.session.last_completion_tokens, locale),
        )
        .replace("{cache}", &cache_summary(app, locale))
        .replace("{total}", &app.session.total_tokens.to_string())
        .replace(
            "{cost}",
            &app.format_cost_amount_precise(app.session_cost_for_currency(app.cost_currency)),
        )
        .replace("{api_messages}", &message_count.to_string())
        .replace("{chat_messages}", &chat_count.to_string())
        .replace("{model}", &app.model);
    CommandResult::message(report)
}

/// Show session cost breakdown
pub fn cost(app: &mut App) -> CommandResult {
    let report = tr(app.ui_locale, MessageId::CmdCostReport).replace(
        "{cost}",
        &app.format_cost_amount_precise(app.session_cost_for_currency(app.cost_currency)),
    );
    CommandResult::message(report)
}

/// Show current system prompt
pub fn system_prompt(app: &mut App) -> CommandResult {
    let prompt_text = match &app.system_prompt {
        Some(SystemPrompt::Text(text)) => text.clone(),
        Some(SystemPrompt::Blocks(blocks)) => blocks
            .iter()
            .map(|b| b.text.clone())
            .collect::<Vec<_>>()
            .join("\n\n---\n\n"),
        None => "(no system prompt)".to_string(),
    };

    // Truncate if too long
    let display = if prompt_text.len() > 500 {
        // Find a valid UTF-8 char boundary at or before byte 500
        let truncate_at = prompt_text
            .char_indices()
            .take_while(|(i, _)| *i <= 500)
            .last()
            .map_or(0, |(i, _)| i);
        format!(
            "{}...\n\n(truncated, {} chars total)",
            &prompt_text[..truncate_at],
            prompt_text.len()
        )
    } else {
        prompt_text
    };

    CommandResult::message(format!(
        "System Prompt ({} mode):\n─────────────────────────────\n{}",
        app.mode.label(),
        display
    ))
}

/// Show context window usage
pub fn context(_app: &mut App) -> CommandResult {
    CommandResult::action(AppAction::OpenContextInspector)
}

/// Show per-turn DeepSeek prefix-cache telemetry for the last N turns (#263).
///
/// `arg` is parsed as a count override (default 10, capped at the ring size).
/// Renders a fixed-width table the user can paste into a bug report.
pub fn cache(app: &mut App, arg: Option<&str>) -> CommandResult {
    let want = arg
        .and_then(|s| s.trim().parse::<usize>().ok())
        .unwrap_or(10);
    let cap = app.session.turn_cache_history.len();
    let count = want
        .min(cap)
        .min(crate::tui::app::App::TURN_CACHE_HISTORY_CAP);

    if cap == 0 {
        return CommandResult::message(tr(app.ui_locale, MessageId::CmdCacheNoData));
    }

    CommandResult::message(format_cache_history(app, count, app.ui_locale))
}

fn format_cache_history(app: &App, count: usize, locale: Locale) -> String {
    let total = app.session.turn_cache_history.len();
    let start = total.saturating_sub(count);
    let rows: Vec<&TurnCacheRecord> = app.session.turn_cache_history.iter().skip(start).collect();

    let mut totals_input: u64 = 0;
    let mut totals_hit: u64 = 0;
    let mut totals_miss: u64 = 0;
    let mut header = tr(locale, MessageId::CmdCacheHeader)
        .replace("{count}", &rows.len().to_string())
        .replace("{total}", &total.to_string())
        .replace("{model}", &app.model);
    header.push_str(&"─".repeat(76));
    header.push('\n');
    header.push_str("turn   in    out   hit   miss   replay   ratio   age\n");
    header.push_str(&"─".repeat(76));
    header.push('\n');

    let now = Instant::now();
    let mut body = String::new();
    let absolute_start = total.saturating_sub(rows.len());
    for (i, rec) in rows.iter().enumerate() {
        let turn_index = absolute_start + i + 1;
        totals_input += u64::from(rec.input_tokens);

        let replay_cell = rec
            .reasoning_replay_tokens
            .map_or_else(|| "—".to_string(), |t| t.to_string());
        let age = humanize_age(now.saturating_duration_since(rec.recorded_at));

        // No cache telemetry → render `—` everywhere and don't pollute totals
        // with inferred zeros. Some providers (and some routes inside DeepSeek)
        // skip the cache fields; including a synthesized 0/N for those turns
        // would make every aggregate ratio look broken.
        let Some(hit) = rec.cache_hit_tokens else {
            body.push_str(&format!(
                "{turn:>4}  {input:>5}  {output:>5}  {hit:>5}  {miss:>5}  {replay:>6}   {ratio:>6}   {age}\n",
                turn = turn_index,
                input = rec.input_tokens,
                output = rec.output_tokens,
                hit = "—",
                miss = "—",
                replay = replay_cell,
                ratio = "—",
                age = age,
            ));
            continue;
        };

        let miss_reported = rec.cache_miss_tokens;
        let miss = miss_reported.unwrap_or_else(|| rec.input_tokens.saturating_sub(hit));
        let accounted = u64::from(hit) + u64::from(miss);
        let ratio = if accounted == 0 {
            "    —".to_string()
        } else {
            format!("{:>5.1}%", 100.0 * f64::from(hit) / accounted as f64)
        };
        totals_hit += u64::from(hit);
        totals_miss += u64::from(miss);

        let miss_cell = match miss_reported {
            Some(_) => format!("{miss}"),
            None => format!("{miss}*"),
        };

        body.push_str(&format!(
            "{turn:>4}  {input:>5}  {output:>5}  {hit:>5}  {miss:>5}  {replay:>6}   {ratio}   {age}\n",
            turn = turn_index,
            input = rec.input_tokens,
            output = rec.output_tokens,
            hit = hit,
            miss = miss_cell,
            replay = replay_cell,
            ratio = ratio,
            age = age,
        ));
    }

    let totals_accounted = totals_hit + totals_miss;
    let avg_ratio = if totals_accounted == 0 {
        "—".to_string()
    } else {
        format!(
            "{:.1}%",
            100.0 * totals_hit as f64 / totals_accounted as f64
        )
    };

    let mut footer = String::new();
    footer.push_str(&"─".repeat(76));
    footer.push('\n');
    footer.push_str(
        &tr(locale, MessageId::CmdCacheTotals)
            .replace("{sum_in}", &totals_input.to_string())
            .replace("{sum_hit}", &totals_hit.to_string())
            .replace("{sum_miss}", &totals_miss.to_string())
            .replace("{avg}", &avg_ratio),
    );
    footer.push_str(tr(locale, MessageId::CmdCacheFootnote));
    footer.push_str(tr(locale, MessageId::CmdCacheAdvice));

    format!("{header}{body}{footer}")
}

fn humanize_age(d: std::time::Duration) -> String {
    let secs = d.as_secs();
    if secs < 60 {
        format!("{secs}s")
    } else if secs < 3600 {
        format!("{}m{:02}s", secs / 60, secs % 60)
    } else {
        format!("{}h{:02}m", secs / 3600, (secs % 3600) / 60)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::config::Config;
    use crate::models::{ContentBlock, Message, SystemBlock};
    use crate::tui::app::{App, TuiOptions};
    use std::path::PathBuf;

    fn create_test_app() -> App {
        let options = TuiOptions {
            model: "deepseek-v4-pro".to_string(),
            workspace: PathBuf::from("/tmp/test-workspace"),
            config_path: None,
            config_profile: None,
            allow_shell: false,
            use_alt_screen: true,
            use_mouse_capture: false,
            use_bracketed_paste: true,
            max_subagents: 1,
            skills_dir: PathBuf::from("/tmp/test-skills"),
            memory_path: PathBuf::from("memory.md"),
            notes_path: PathBuf::from("notes.txt"),
            mcp_config_path: PathBuf::from("mcp.json"),
            use_memory: false,
            start_in_agent_mode: false,
            skip_onboarding: true,
            yolo: false,
            resume_session_id: None,
            initial_input: None,
        };
        let mut app = App::new(options, &Config::default());
        app.ui_locale = crate::localization::Locale::En;
        app.api_provider = crate::config::ApiProvider::Deepseek;
        app
    }

    #[test]
    fn test_tokens_shows_usage_info() {
        let mut app = create_test_app();
        app.session.total_tokens = 1234;
        app.session.session_cost = 0.05;
        app.session.last_prompt_tokens = Some(100);
        app.session.last_completion_tokens = Some(25);
        app.session.last_prompt_cache_hit_tokens = Some(70);
        app.session.last_prompt_cache_miss_tokens = Some(30);
        app.api_messages.push(Message {
            role: "user".to_string(),
            content: vec![ContentBlock::Text {
                text: "test".to_string(),
                cache_control: None,
            }],
        });
        app.history.push(HistoryCell::User {
            content: "test".to_string(),
        });

        let result = tokens(&mut app);
        assert!(result.message.is_some());
        let msg = result.message.unwrap();
        assert!(msg.contains("Token Usage"));
        assert!(msg.contains("Active context:"));
        assert!(msg.contains("Last API input:"));
        assert!(msg.contains("Last API output:"));
        assert!(msg.contains("Cache hit/miss:"));
        assert!(msg.contains("70 hit / 30 miss"));
        assert!(msg.contains("Cumulative tokens:"));
        assert!(msg.contains("Approx session cost:"));
        assert!(msg.contains("API messages:"));
        assert!(msg.contains("Chat messages:"));
        assert!(msg.contains("Model:"));
    }

    #[test]
    fn test_cost_shows_spending_info() {
        let mut app = create_test_app();
        app.session.session_cost = 0.1234;
        let result = cost(&mut app);
        assert!(result.message.is_some());
        let msg = result.message.unwrap();
        assert!(msg.contains("Session Cost"));
        assert!(msg.contains("Approx total spent:"));
        assert!(msg.contains("approximate"));
        assert!(msg.contains("$0.1234"));
    }

    #[test]
    fn test_system_prompt_displays_text() {
        let mut app = create_test_app();
        app.system_prompt = Some(SystemPrompt::Text("Test system prompt".to_string()));
        let result = system_prompt(&mut app);
        assert!(result.message.is_some());
        let msg = result.message.unwrap();
        assert!(msg.contains("System Prompt"));
        assert!(msg.contains("Test system prompt"));
    }

    #[test]
    fn test_system_prompt_displays_blocks() {
        let mut app = create_test_app();
        app.system_prompt = Some(SystemPrompt::Blocks(vec![
            SystemBlock {
                block_type: "text".to_string(),
                text: "Block 1".to_string(),
                cache_control: None,
            },
            SystemBlock {
                block_type: "text".to_string(),
                text: "Block 2".to_string(),
                cache_control: None,
            },
        ]));
        let result = system_prompt(&mut app);
        assert!(result.message.is_some());
        let msg = result.message.unwrap();
        assert!(msg.contains("System Prompt"));
        assert!(msg.contains("Block 1"));
        assert!(msg.contains("Block 2"));
    }

    #[test]
    fn test_system_prompt_none() {
        let mut app = create_test_app();
        app.system_prompt = None;
        let result = system_prompt(&mut app);
        assert!(result.message.is_some());
        let msg = result.message.unwrap();
        assert!(msg.contains("(no system prompt)"));
    }

    #[test]
    fn test_system_prompt_truncates_long_text() {
        let mut app = create_test_app();
        let long_text = "x".repeat(600);
        app.system_prompt = Some(SystemPrompt::Text(long_text));
        let result = system_prompt(&mut app);
        assert!(result.message.is_some());
        let msg = result.message.unwrap();
        assert!(msg.contains("..."));
        assert!(msg.contains("chars total"));
    }

    #[test]
    fn cache_command_reports_no_data_before_first_turn() {
        let mut app = create_test_app();
        let result = cache(&mut app, None);
        let msg = result.message.expect("cache produces a message");
        assert!(msg.contains("no turns recorded yet"), "got: {msg}");
    }

    #[test]
    fn cache_command_renders_recorded_turns_with_ratio() {
        let mut app = create_test_app();
        let now = Instant::now();
        // Three turns: 75% hit, 50% hit, miss-only (provider didn't report hit).
        app.push_turn_cache_record(TurnCacheRecord {
            input_tokens: 4_000,
            output_tokens: 200,
            cache_hit_tokens: Some(3_000),
            cache_miss_tokens: Some(1_000),
            reasoning_replay_tokens: None,
            recorded_at: now,
        });
        app.push_turn_cache_record(TurnCacheRecord {
            input_tokens: 6_000,
            output_tokens: 250,
            cache_hit_tokens: Some(3_000),
            cache_miss_tokens: Some(3_000),
            reasoning_replay_tokens: Some(150),
            recorded_at: now,
        });
        // Turn 3: hit reported but provider didn't report miss separately —
        // infer miss = input − hit and mark with `*`.
        app.push_turn_cache_record(TurnCacheRecord {
            input_tokens: 5_000,
            output_tokens: 100,
            cache_hit_tokens: Some(2_500),
            cache_miss_tokens: None,
            reasoning_replay_tokens: None,
            recorded_at: now,
        });
        // Turn 4: no telemetry at all — must not pollute aggregate ratios.
        app.push_turn_cache_record(TurnCacheRecord {
            input_tokens: 1_000,
            output_tokens: 50,
            cache_hit_tokens: None,
            cache_miss_tokens: None,
            reasoning_replay_tokens: None,
            recorded_at: now,
        });

        let result = cache(&mut app, None);
        let msg = result.message.expect("cache produces a message");

        // Header reflects total rows and model.
        assert!(msg.contains("last 4 of 4 turn(s)"), "got: {msg}");
        // Per-turn ratios are rendered.
        assert!(msg.contains("75.0%"), "got: {msg}");
        assert!(msg.contains("50.0%"), "got: {msg}");
        // Turn 3: hit=2500, inferred miss=2500 → 50.0% with `*`-marked miss.
        assert!(msg.contains("2500*"), "got: {msg}");
        // Turn 4 (no telemetry) shows em-dashes and is excluded from totals.
        // Aggregate over turns 1-3: hit=8500, miss=6500 → 56.7%.
        assert!(msg.contains("avg hit ratio: 56.7%"), "got: {msg}");
        // Footer guidance is present.
        assert!(msg.contains("70%"), "got: {msg}");
    }

    #[test]
    fn cache_command_count_argument_clamps_to_history() {
        let mut app = create_test_app();
        for _ in 0..3 {
            app.push_turn_cache_record(TurnCacheRecord {
                input_tokens: 1_000,
                output_tokens: 100,
                cache_hit_tokens: Some(500),
                cache_miss_tokens: Some(500),
                reasoning_replay_tokens: None,
                recorded_at: Instant::now(),
            });
        }
        let result = cache(&mut app, Some("100"));
        let msg = result.message.expect("cache produces a message");
        // Asked for 100 turns, only 3 exist — should report "last 3 of 3".
        assert!(msg.contains("last 3 of 3 turn(s)"), "got: {msg}");
    }

    #[test]
    fn turn_cache_history_is_capped_at_50() {
        let mut app = create_test_app();
        for i in 0..(crate::tui::app::App::TURN_CACHE_HISTORY_CAP + 12) {
            app.push_turn_cache_record(TurnCacheRecord {
                input_tokens: i as u32,
                output_tokens: 1,
                cache_hit_tokens: Some(i as u32),
                cache_miss_tokens: Some(0),
                reasoning_replay_tokens: None,
                recorded_at: Instant::now(),
            });
        }
        assert_eq!(
            app.session.turn_cache_history.len(),
            crate::tui::app::App::TURN_CACHE_HISTORY_CAP
        );
        // Oldest record was evicted; newest record is still at the back.
        assert_eq!(
            app.session.turn_cache_history.back().unwrap().input_tokens,
            (crate::tui::app::App::TURN_CACHE_HISTORY_CAP + 11) as u32
        );
    }

    #[test]
    fn test_context_shows_usage_stats() {
        let mut app = create_test_app();
        app.api_messages.push(Message {
            role: "user".to_string(),
            content: vec![ContentBlock::Text {
                text: "Hello".to_string(),
                cache_control: None,
            }],
        });
        app.history.push(HistoryCell::User {
            content: "Hello".to_string(),
        });

        let result = context(&mut app);
        assert!(matches!(
            result.action,
            Some(AppAction::OpenContextInspector)
        ));
        assert!(result.message.is_none());
    }

    #[test]
    fn test_undo_conversation_removes_last_exchange() {
        let mut app = create_test_app();
        app.history.push(HistoryCell::User {
            content: "Hello".to_string(),
        });
        app.history.push(HistoryCell::Assistant {
            content: "Hi".to_string(),
            streaming: false,
        });
        app.api_messages.push(Message {
            role: "user".to_string(),
            content: vec![],
        });
        app.api_messages.push(Message {
            role: "assistant".to_string(),
            content: vec![],
        });

        let initial_history_len = app.history.len();
        let initial_api_len = app.api_messages.len();
        let result = undo_conversation(&mut app);

        assert!(result.message.is_some());
        let msg = result.message.unwrap();
        assert!(msg.contains("Removed"));
        assert!(app.history.len() < initial_history_len);
        assert!(app.api_messages.len() < initial_api_len);
    }

    #[test]
    fn test_undo_conversation_nothing_to_undo() {
        let mut app = create_test_app();
        // Clear any default history
        app.history.clear();
        app.api_messages.clear();
        let result = undo_conversation(&mut app);
        assert!(result.message.is_some());
        let msg = result.message.unwrap();
        assert!(msg.contains("Nothing to undo") || msg.contains("Removed"));
    }

    #[test]
    fn test_retry_with_previous_message() {
        let mut app = create_test_app();
        app.history.push(HistoryCell::User {
            content: "Test message".to_string(),
        });
        app.history.push(HistoryCell::Assistant {
            content: "Response".to_string(),
            streaming: false,
        });

        let result = retry(&mut app);
        assert!(result.message.is_some());
        let msg = result.message.unwrap();
        assert!(msg.contains("Retrying"));
        assert!(msg.contains("Test message"));
        assert!(matches!(result.action, Some(AppAction::SendMessage(_))));
    }

    #[test]
    fn test_retry_no_previous_message() {
        let mut app = create_test_app();
        let result = retry(&mut app);
        assert!(result.message.is_some());
        let msg = result.message.unwrap();
        assert!(msg.contains("No previous request to retry"));
        assert!(result.action.is_none());
    }

    #[test]
    fn test_retry_truncates_long_input() {
        let mut app = create_test_app();
        let long_input = "x".repeat(100);
        app.history.push(HistoryCell::User {
            content: long_input.clone(),
        });
        app.history.push(HistoryCell::Assistant {
            content: "Response".to_string(),
            streaming: false,
        });

        let result = retry(&mut app);
        assert!(result.message.is_some());
        let msg = result.message.unwrap();
        assert!(msg.contains("Retrying"));
        assert!(msg.contains("..."));
    }
}

/// Remove last message pair (user + assistant).
///
/// This is the old `/undo` behaviour — it removes the most recent
/// user+assistant conversation pair from history and API messages.
/// The new `/undo` first tries to revert workspace files via
/// [`patch_undo`]; if no snapshots are available it falls back to
/// this function.
pub fn undo_conversation(app: &mut App) -> CommandResult {
    // Remove from display history (up to the last user message)
    let mut removed_count = 0;
    while !app.history.is_empty() {
        let last_is_user = matches!(app.history.last(), Some(HistoryCell::User { .. }));
        app.pop_history();
        removed_count += 1;
        if last_is_user {
            break;
        }
    }

    // Remove from API messages
    while let Some(last) = app.api_messages.last() {
        if last.role == "user" {
            app.api_messages.pop();
            break;
        }
        app.api_messages.pop();
    }

    if removed_count > 0 {
        // Keep tool/index mappings consistent after truncation.
        app.tool_cells.clear();
        app.tool_details_by_cell.clear();
        app.exploring_entries.clear();
        app.ignored_tool_calls.clear();
        app.mark_history_updated();
        CommandResult::message(format!("Removed {removed_count} message(s)"))
    } else {
        CommandResult::message("Nothing to undo")
    }
}

/// Revert the most recent write tool (apply_patch/edit_file/write_file) or turn.
///
/// Opens the side-git snapshot repo and finds the most recent snapshot,
/// preferring per-tool snapshots (`tool:*`) over pre-turn snapshots
/// (`pre-turn:*`). Restores files from that snapshot and shows a diff
/// summary. Falls back to conversation undo when no snapshots exist.
///
/// Posts a `HistoryCell::System` entry so the user can see what was
/// reverted in the transcript.
pub fn patch_undo(app: &mut App) -> CommandResult {
    let workspace = app.workspace.clone();

    let repo = match crate::snapshot::SnapshotRepo::open_or_init(&workspace) {
        Ok(r) => r,
        Err(e) => {
            return CommandResult::error(format!(
                "Snapshot repo unavailable for {}: {e}",
                workspace.display(),
            ));
        }
    };

    let snapshots = match repo.list(20) {
        Ok(s) => s,
        Err(e) => {
            return CommandResult::error(format!("Failed to list snapshots: {e}"));
        }
    };

    if snapshots.is_empty() {
        return CommandResult::message("No snapshots found to undo — nothing to revert.");
    }

    // Prefer the most recent `tool:` snapshot; fall back to `pre-turn:`.
    let target = snapshots
        .iter()
        .find(|s| s.label.starts_with("tool:"))
        .or_else(|| snapshots.iter().find(|s| s.label.starts_with("pre-turn:")));

    let Some(target) = target else {
        return CommandResult::message("No tool or pre-turn snapshots found — nothing to revert.");
    };

    if let Err(e) = repo.restore(&target.id) {
        return CommandResult::error(format!("Restore failed: {e}"));
    }

    // Show diff stat so the user knows what changed.
    let diff_stat = std::process::Command::new("git")
        .args(["diff", "--stat"])
        .current_dir(&workspace)
        .output()
        .ok()
        .and_then(|o| {
            let s = String::from_utf8_lossy(&o.stdout).trim().to_string();
            if s.is_empty() { None } else { Some(s) }
        });

    let short = &target.id.as_str()[..target.id.as_str().len().min(8)];
    let summary = match diff_stat {
        Some(ref stat) => {
            format!(
                "Restored snapshot '{}' ({}). Files affected:\n{stat}",
                target.label, short
            )
        }
        None => {
            format!(
                "Restored snapshot '{}' ({}). No diff changes detected.",
                target.label, short
            )
        }
    };

    // Post a system cell so the reverted state is visible in the transcript.
    app.push_history_cell(HistoryCell::System {
        content: format!(
            "/undo reverted workspace to snapshot '{}' ({})",
            target.label, short
        ),
    });

    CommandResult::message(summary)
}

/// Load the last user message back into the composer for editing.
///
/// Searches `app.history` for the most recent `HistoryCell::User`, copies its
/// content into `app.input`, and positions the cursor at the end so the user
/// can edit and press Enter to resubmit. The original exchange stays visible
/// in the transcript.
pub fn edit(app: &mut App) -> CommandResult {
    let last_user = app.history.iter().rev().find_map(|cell| match cell {
        HistoryCell::User { content } => Some(content.clone()),
        _ => None,
    });

    match last_user {
        Some(content) => {
            app.input = content;
            app.cursor_position = app.input.chars().count();
            app.edit_in_progress = true;
            CommandResult::message(
                "Last message loaded into composer — edit and press Enter to resubmit",
            )
        }
        None => CommandResult::message("No previous message to edit"),
    }
}

/// Show git diff output since session start.
///
/// Runs `git diff --stat` and `git diff --name-only` in the workspace
/// directory. Displays which files have changed and a stat summary. If no
/// changes exist or git fails, returns an appropriate message.
pub fn diff(app: &mut App) -> CommandResult {
    let workspace = app.workspace.clone();

    let name_only_output = std::process::Command::new("git")
        .args(["diff", "--name-only"])
        .current_dir(&workspace)
        .output();
    let stat_output = std::process::Command::new("git")
        .args(["diff", "--stat"])
        .current_dir(&workspace)
        .output();

    match (name_only_output, stat_output) {
        (Ok(name_only), Ok(stat)) => {
            let name_stdout = String::from_utf8_lossy(&name_only.stdout);
            let stat_stdout = String::from_utf8_lossy(&stat.stdout);

            if name_stdout.trim().is_empty() {
                return CommandResult::message("No changes since session start");
            }

            let files: Vec<&str> = name_stdout.lines().filter(|l| !l.is_empty()).collect();
            let file_count = files.len();
            let file_list = files.join("\n");

            // Detect rename entries (e.g. "foo -> bar") and exclude them
            // from the file-count header so the user sees only actual
            // modifications.
            let renamed_count = files.iter().filter(|f| f.contains(" -> ")).count();
            let summary = if renamed_count > 0 {
                format!("Changed files ({file_count}, {renamed_count} renamed):\n{file_list}")
            } else {
                format!("Changed files ({file_count}):\n{file_list}")
            };

            let stat_str = stat_stdout.trim();
            let mut message = summary;
            if !stat_str.is_empty() {
                message.push_str("\n\n── Stat ──\n");
                message.push_str(stat_str);
            }
            CommandResult::message(message)
        }
        (Err(e), _) | (_, Err(e)) => {
            CommandResult::message(format!("Git diff failed — is this a git repository?\n{e}"))
        }
    }
}

/// Retry last request - remove last exchange and re-send the user's message
pub fn retry(app: &mut App) -> CommandResult {
    let last_user_input = app.history.iter().rev().find_map(|cell| match cell {
        HistoryCell::User { content } => Some(content.clone()),
        _ => None,
    });

    match last_user_input {
        Some(input) => {
            undo_conversation(app);
            let display_input = if input.len() > 50 {
                let truncate_at = input
                    .char_indices()
                    .take_while(|(i, _)| *i <= 50)
                    .last()
                    .map_or(0, |(i, _)| i);
                format!("{}...", &input[..truncate_at])
            } else {
                input.clone()
            };
            CommandResult::with_message_and_action(
                format!("Retrying: {display_input}"),
                AppAction::SendMessage(input),
            )
        }
        None => CommandResult::error("No previous request to retry"),
    }
}