//! Diagnostics: panic hook, frontend error capture, and the manual
//! diagnostic-report bundler used by Settings → About.
//!
//! Privacy posture (matches Kon's local-first positioning):
//! - All capture is to disk only. Nothing is transmitted.
//! - The manual report bundler shows the user exactly what would be
//!   shared and lets them choose to copy/save/email it.
//! - No remote endpoint, no Sentry, no opt-out telemetry.

use std::fs;
use std::io::Write;
use std::panic;
use std::path::PathBuf;
use std::time::{SystemTime, UNIX_EPOCH};

use serde::{Deserialize, Serialize};

use kon_storage::{
    app_data_dir, crashes_dir, list_recent_errors, log_error, logs_dir, ErrorLogRow,
};

use crate::commands::power::active_assertions_snapshot;
use crate::commands::security::ensure_main_window;
use crate::AppState;

const DEFAULT_RECENT_ERRORS: i64 = 50;
const KON_VERSION: &str = env!("CARGO_PKG_VERSION");

/// Install the Rust panic hook. Writes each panic to a separate file in
/// crashes_dir so the diagnostic-report bundler can attach them. Also
/// keeps the default panic message on stderr so terminal users see it.
///
/// Called once at startup before tauri::Builder.
pub fn install_panic_hook() {
    if let Err(e) = fs::create_dir_all(crashes_dir()) {
        eprintln!("[diagnostics] could not create crashes dir: {e}");
        return;
    }

    let default_hook = panic::take_hook();
    panic::set_hook(Box::new(move |info| {
        // Write a minimal text dump. Backtraces require RUST_BACKTRACE=1
        // and the std::backtrace API; we capture what's free.
        let ts = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .map(|d| d.as_secs())
            .unwrap_or(0);
        let short = (ts % 0xFFFF) as u16;
        let path = crashes_dir().join(format!("{ts}-{short:04x}.crash"));

        let payload = format!(
            "Kon crash dump\n\
             ==============\n\
             Version: {ver}\n\
             Timestamp: {ts} (UTC seconds)\n\
             Thread: {thread}\n\
             \n\
             Panic message:\n\
             {info}\n\
             \n\
             OS: {os} {arch}\n\
             RUST_BACKTRACE: {bt}\n",
            ver = KON_VERSION,
            ts = ts,
            thread = std::thread::current().name().unwrap_or("<unnamed>"),
            info = info,
            os = std::env::consts::OS,
            arch = std::env::consts::ARCH,
            bt = std::env::var("RUST_BACKTRACE").unwrap_or_else(|_| "0".to_string()),
        );

        if let Ok(mut f) = fs::File::create(&path) {
            let _ = f.write_all(payload.as_bytes());
        }

        // Still call the original hook so the panic shows in the terminal.
        default_hook(info);
    }));
}

/// Tauri command: persist a frontend-side error to error_log.
///
/// Wired from the global window.onerror + window.unhandledrejection
/// handlers in the Svelte root layout. Also called explicitly by
/// invokeWithToast on failure paths so we have a unified record.
#[tauri::command]
pub async fn log_frontend_error(
    state: tauri::State<'_, AppState>,
    context: String,
    message: String,
    stack: Option<String>,
) -> Result<(), String> {
    let metadata = stack.map(|s| {
        // Truncate stacks to keep the table from bloating; the full stack
        // is also visible in the browser console anyway.
        s.chars().take(2000).collect::<String>()
    });

    log_error(
        &state.db,
        if context.is_empty() {
            "frontend"
        } else {
            &context
        },
        Some("FRONTEND_ERROR"),
        &message,
        metadata.as_deref(),
    )
    .await
    .map_err(|e| e.to_string())
}

#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct ErrorLogDto {
    pub id: i64,
    pub timestamp: String,
    pub context: String,
    pub error_code: Option<String>,
    pub message: String,
    pub metadata: Option<String>,
}

impl From<ErrorLogRow> for ErrorLogDto {
    fn from(r: ErrorLogRow) -> Self {
        Self {
            id: r.id,
            timestamp: r.timestamp,
            context: r.context,
            error_code: r.error_code,
            message: r.message,
            metadata: r.metadata,
        }
    }
}

#[tauri::command]
pub async fn list_recent_errors_command(
    window: tauri::WebviewWindow,
    state: tauri::State<'_, AppState>,
    limit: Option<i64>,
) -> Result<Vec<ErrorLogDto>, String> {
    ensure_main_window(&window)?;
    let n = limit.unwrap_or(DEFAULT_RECENT_ERRORS).clamp(1, 1000);
    list_recent_errors(&state.db, n)
        .await
        .map(|rows| rows.into_iter().map(ErrorLogDto::from).collect())
        .map_err(|e| e.to_string())
}

/// One crash file on disk.
#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct CrashFile {
    pub filename: String,
    pub mtime_secs: u64,
    pub size_bytes: u64,
    pub preview: String, // first ~600 chars
}

#[tauri::command]
pub async fn list_crash_files(window: tauri::WebviewWindow) -> Result<Vec<CrashFile>, String> {
    ensure_main_window(&window)?;
    list_crash_files_inner().await
}

async fn list_crash_files_inner() -> Result<Vec<CrashFile>, String> {
    let dir = crashes_dir();
    let entries = match fs::read_dir(&dir) {
        Ok(e) => e,
        Err(_) => return Ok(Vec::new()), // no crashes dir = no crashes, perfect
    };

    let mut out: Vec<CrashFile> = Vec::new();
    for entry in entries.flatten() {
        let path = entry.path();
        if path.extension().and_then(|s| s.to_str()) != Some("crash") {
            continue;
        }
        let meta = match fs::metadata(&path) {
            Ok(m) => m,
            Err(_) => continue,
        };
        let mtime_secs = meta
            .modified()
            .ok()
            .and_then(|t| t.duration_since(UNIX_EPOCH).ok())
            .map(|d| d.as_secs())
            .unwrap_or(0);
        let size_bytes = meta.len();
        let preview = match fs::read_to_string(&path) {
            Ok(s) => s.chars().take(600).collect::<String>(),
            Err(_) => String::new(),
        };
        out.push(CrashFile {
            filename: path
                .file_name()
                .and_then(|s| s.to_str())
                .map(String::from)
                .unwrap_or_default(),
            mtime_secs,
            size_bytes,
            preview,
        });
    }
    // Newest first
    out.sort_by(|a, b| b.mtime_secs.cmp(&a.mtime_secs));
    Ok(out)
}

#[derive(Debug, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct ReportOptions {
    pub include_recent_errors: bool,
    pub include_crashes: bool,
    pub include_settings: bool,
    pub include_log_tail: bool,
}

impl Default for ReportOptions {
    fn default() -> Self {
        Self {
            include_recent_errors: true,
            include_crashes: true,
            include_settings: false,
            include_log_tail: false,
        }
    }
}

fn redact_home(input: &str) -> String {
    match std::env::var("HOME") {
        Ok(home) if !home.is_empty() => input.replace(&home, "~"),
        _ => input.to_string(),
    }
}

fn looks_sensitive_key(key: &str) -> bool {
    let lower = key.to_ascii_lowercase();
    lower.contains("path")
        || lower.contains("folder")
        || lower.contains("directory")
        || lower.contains("device")
        || lower.contains("microphone")
}

fn redact_json_value(value: &mut serde_json::Value, key_hint: Option<&str>) {
    match value {
        serde_json::Value::Object(map) => {
            for (key, child) in map.iter_mut() {
                redact_json_value(child, Some(key));
            }
        }
        serde_json::Value::Array(items) => {
            for item in items {
                redact_json_value(item, key_hint);
            }
        }
        serde_json::Value::String(text) => {
            if key_hint.map(looks_sensitive_key).unwrap_or(false)
                || text.starts_with('/')
                || text.contains(":\\")
                || text.contains("/home/")
                || text.contains("/Users/")
            {
                *text = redact_home(text);
            }
        }
        _ => {}
    }
}

fn sanitise_preferences_json(raw: &str) -> String {
    match serde_json::from_str::<serde_json::Value>(raw) {
        Ok(mut value) => {
            redact_json_value(&mut value, None);
            serde_json::to_string_pretty(&value).unwrap_or_else(|_| "{}".to_string())
        }
        Err(_) => "_preferences could not be parsed as JSON_".to_string(),
    }
}

fn redact_line(input: &str) -> String {
    redact_home(input)
        .chars()
        .take(400)
        .collect::<String>()
        .replace('\n', " ")
}

/// Build a single human-readable diagnostic-report string. The user inspects
/// this in Settings → About before deciding whether to copy/save/email it.
///
/// The string is plain markdown so it can be pasted into an email, a
/// Discord thread, or a GitHub issue without further conversion.
#[tauri::command]
pub async fn generate_diagnostic_report(
    window: tauri::WebviewWindow,
    state: tauri::State<'_, AppState>,
    options: Option<ReportOptions>,
) -> Result<String, String> {
    ensure_main_window(&window)?;
    generate_diagnostic_report_inner(&state, options).await
}

async fn generate_diagnostic_report_inner(
    state: &tauri::State<'_, AppState>,
    options: Option<ReportOptions>,
) -> Result<String, String> {
    let opts = options.unwrap_or_default();
    let mut out = String::new();

    out.push_str("# Kon diagnostic report\n\n");
    out.push_str(&format!("- Version: `{}`\n", KON_VERSION));
    out.push_str(&format!(
        "- OS / arch: `{} / {}`\n",
        std::env::consts::OS,
        std::env::consts::ARCH
    ));
    out.push_str(&format!(
        "- App data dir: `{}`\n",
        redact_home(&app_data_dir().display().to_string())
    ));
    let now = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_secs())
        .unwrap_or(0);
    out.push_str(&format!("- Generated: unix `{}`\n", now));
    out.push('\n');
    out.push_str(
        "> This report is local-only until you choose to share it. \
                  Review the contents below before sending to anyone.\n\n",
    );

    if opts.include_settings {
        out.push_str("## Settings (sanitised)\n\n");
        match kon_storage::get_setting(&state.db, "kon_preferences").await {
            Ok(Some(json)) => {
                out.push_str("```json\n");
                out.push_str(&sanitise_preferences_json(&json));
                out.push_str("\n```\n\n");
            }
            Ok(None) => out.push_str("_(no preferences saved)_\n\n"),
            Err(e) => out.push_str(&format!("_(could not read preferences: {e})_\n\n")),
        }
    }

    if opts.include_recent_errors {
        out.push_str("## Recent errors (newest first)\n\n");
        match list_recent_errors(&state.db, DEFAULT_RECENT_ERRORS).await {
            Ok(rows) if rows.is_empty() => out.push_str("_(no errors logged)_\n\n"),
            Ok(rows) => {
                for r in rows {
                    out.push_str(&format!(
                        "- `{}` **{}** [{}]{}: {}\n",
                        r.timestamp,
                        r.context,
                        r.error_code.as_deref().unwrap_or("?"),
                        if r.metadata.is_some() { " (+meta)" } else { "" },
                        redact_line(&r.message),
                    ));
                }
                out.push('\n');
            }
            Err(e) => out.push_str(&format!("_(could not read error log: {e})_\n\n")),
        }
    }

    out.push_str("## Power assertions\n\n");
    let power_assertions = active_assertions_snapshot();
    if power_assertions.is_empty() {
        out.push_str("_(no active power assertions at report time)_\n\n");
    } else {
        for assertion in power_assertions {
            out.push_str(&format!(
                "- `#{}` reason=`{}` backend=`{}` acquired=`{}`\n",
                assertion.id, assertion.reason, assertion.backend, assertion.acquired
            ));
        }
        out.push('\n');
    }

    if opts.include_crashes {
        out.push_str("## Crash dumps\n\n");
        let crashes = list_crash_files_inner().await.unwrap_or_default();
        if crashes.is_empty() {
            out.push_str("_(no crash dumps on disk — nothing has crashed)_\n\n");
        } else {
            for c in crashes.iter().take(5) {
                out.push_str(&format!(
                    "### `{}` ({} bytes)\n\n```\n{}\n```\n\n",
                    c.filename, c.size_bytes, c.preview
                ));
            }
            if crashes.len() > 5 {
                out.push_str(&format!(
                    "_(plus {} older crash dumps in `{}`)_\n\n",
                    crashes.len() - 5,
                    redact_home(&crashes_dir().display().to_string())
                ));
            }
        }
    }

    if opts.include_log_tail {
        out.push_str("## Log tail\n\n");
        let log_path = logs_dir().join("kon.log");
        match read_tail(&log_path, 8000) {
            Ok(tail) if tail.is_empty() => {
                out.push_str("_(log file empty or not yet written)_\n\n");
            }
            Ok(tail) => {
                out.push_str("```\n");
                out.push_str(&redact_home(&tail));
                out.push_str("\n```\n\n");
            }
            Err(_) => out.push_str("_(no log file found)_\n\n"),
        }
    }

    out.push_str("---\n\n");
    out.push_str(
        "Generated by Kon. To share, copy the entire markdown above \
                  and paste it into an email or issue. Email: jake@corbel.consulting.\n",
    );

    Ok(out)
}

/// Read the last `n_bytes` of a file as a UTF-8 string, lossy-decoded.
/// Used to show recent log content without loading huge files.
fn read_tail(path: &PathBuf, n_bytes: u64) -> std::io::Result<String> {
    use std::io::{Read, Seek, SeekFrom};
    let mut f = fs::File::open(path)?;
    let len = f.metadata()?.len();
    let start = len.saturating_sub(n_bytes);
    f.seek(SeekFrom::Start(start))?;
    let mut buf = Vec::new();
    f.read_to_end(&mut buf)?;
    Ok(String::from_utf8_lossy(&buf).to_string())
}

/// Cross-platform OS info exposed to the frontend so the UI can adapt:
/// hotkey labels (Cmd vs Ctrl), file-picker text, "open file location"
/// terminology, etc. Returned on demand via the `get_os_info` Tauri
/// command rather than recomputed in JS so we have a single source of
/// truth in the Rust layer.
#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct OsInfo {
    /// "windows" | "macos" | "linux" | "ios" | "android" | other
    pub os: String,
    /// "x86_64" | "aarch64" | other
    pub arch: String,
    /// Human-readable platform family for tooltips: "Windows", "macOS",
    /// "Linux"
    pub family: String,
    /// True if the platform uses the Cmd modifier rather than Ctrl as
    /// the primary accelerator (macOS).
    pub uses_cmd: bool,
    /// True if the user is currently in a Wayland session (Linux only).
    /// Useful for status display; the actual workaround is automatic.
    pub is_wayland: bool,
    /// True if the custom evdev hotkey listener is the primary backend
    /// (Linux only). Otherwise the Tauri global-shortcut plugin is used.
    pub custom_hotkey_backend: bool,
    /// Convenience: a localised label for the primary modifier
    /// ("Cmd" on macOS, "Ctrl" elsewhere).
    pub primary_modifier_label: String,
}

#[tauri::command]
pub fn get_os_info() -> OsInfo {
    let os = std::env::consts::OS.to_string();
    let arch = std::env::consts::ARCH.to_string();
    let family = match os.as_str() {
        "windows" => "Windows",
        "macos" => "macOS",
        "linux" => "Linux",
        "ios" => "iOS",
        "android" => "Android",
        _ => "Unknown",
    }
    .to_string();
    let uses_cmd = os == "macos";
    let primary_modifier_label = if uses_cmd { "Cmd" } else { "Ctrl" }.to_string();

    let is_wayland = if os == "linux" {
        std::env::var("XDG_SESSION_TYPE")
            .map(|v| v.eq_ignore_ascii_case("wayland"))
            .unwrap_or(false)
    } else {
        false
    };

    let custom_hotkey_backend = os == "linux";

    OsInfo {
        os,
        arch,
        family,
        uses_cmd,
        is_wayland,
        custom_hotkey_backend,
        primary_modifier_label,
    }
}

/// Write the report to a file and return the path. Lets the user save it
/// somewhere they can attach to an email.
#[tauri::command]
pub async fn save_diagnostic_report(
    window: tauri::WebviewWindow,
    app: tauri::AppHandle,
    state: tauri::State<'_, AppState>,
    options: Option<ReportOptions>,
) -> Result<String, String> {
    ensure_main_window(&window)?;
    let _ = app; // reserved for future dialog integration
    let report = generate_diagnostic_report_inner(&state, options).await?;

    let dir = kon_storage::app_data_dir().join("diagnostic-reports");
    fs::create_dir_all(&dir).map_err(|e| format!("create dir: {e}"))?;

    let ts = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_secs())
        .unwrap_or(0);
    let path = dir.join(format!("kon-diagnostic-{ts}.md"));

    fs::write(&path, &report).map_err(|e| format!("write file: {e}"))?;
    Ok(path.to_string_lossy().to_string())
}