use argon2::{Algorithm, Argon2, Params, Version};
use rand::RngCore;
use serde::{Deserialize, Serialize};
use sha2::{Digest, Sha256, Sha384};
use std::fs;
use std::path::{Path, PathBuf};
use subtle::ConstantTimeEq;
use tauri::Manager;

use crate::database;
use crate::database::profile_db;

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Profile {
    pub id: String,
    pub name: String,
    pub color: String,
    pub pin_hash: Option<String>,
    pub db_filename: String,
    pub created_at: String,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ProfilesConfig {
    pub active_profile_id: String,
    pub profiles: Vec<Profile>,
}

fn get_profiles_path(app: &tauri::AppHandle) -> Result<std::path::PathBuf, String> {
    let app_dir = app
        .path()
        .app_data_dir()
        .map_err(|e| format!("Cannot get app data dir: {}", e))?;
    Ok(app_dir.join("profiles.json"))
}

/// Folder where tauri-plugin-sql keeps every profile database.
///
/// The plugin opens `sqlite:<file>` under `app_config_dir()` (tauri-plugin-sql
/// 2.3.2, `wrapper.rs`: `DbPool::connect` then `path_mapper`), not under
/// `app_data_dir()`, where `profiles.json` and the licence files live. Both
/// are the same folder on Windows and macOS, not on Linux (`~/.config/<id>`
/// and `~/.local/share/<id>`): until #390, every command that looked for a
/// profile database under `app_data_dir()` found nothing on Linux.
pub(crate) fn profile_db_dir<R: tauri::Runtime>(app: &tauri::AppHandle<R>) -> Result<PathBuf, String> {
    app.path()
        .app_config_dir()
        .map_err(|e| format!("Cannot get app config dir: {}", e))
}

/// Path of a profile database, from the bare file name the webview passes.
pub(crate) fn profile_db_path<R: tauri::Runtime>(
    app: &tauri::AppHandle<R>,
    db_filename: &str,
) -> Result<PathBuf, String> {
    profile_db_path_in(&profile_db_dir(app)?, db_filename)
}

/// Accept only the two shapes the app ever gives a profile database:
/// `simpl_resultat.db` and `profile_<hex>.db` (ProfileContext, since v0.3.0).
/// `Path::join` with an absolute value would replace the folder, and these
/// commands write and delete.
pub(crate) fn profile_db_path_in(dir: &Path, db_filename: &str) -> Result<PathBuf, String> {
    if !is_profile_db_filename(db_filename) {
        return Err("invalid_profile_db_filename".to_string());
    }
    Ok(dir.join(db_filename))
}

fn is_profile_db_filename(name: &str) -> bool {
    if name == database::DEFAULT_PROFILE_DB {
        return true;
    }
    match name.strip_prefix("profile_").and_then(|rest| rest.strip_suffix(".db")) {
        Some(id) => !id.is_empty() && id.bytes().all(|b| b.is_ascii_hexdigit()),
        None => false,
    }
}

fn make_default_config() -> ProfilesConfig {
    let now = chrono_now();
    let default_id = "default".to_string();
    ProfilesConfig {
        active_profile_id: default_id.clone(),
        profiles: vec![Profile {
            id: default_id,
            name: "Default".to_string(),
            color: "#4A90A4".to_string(),
            pin_hash: None,
            db_filename: "simpl_resultat.db".to_string(),
            created_at: now,
        }],
    }
}

fn chrono_now() -> String {
    // Simple ISO-ish timestamp without pulling in chrono crate
    let dur = std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .unwrap_or_default();
    let secs = dur.as_secs();
    // Return as unix timestamp string — frontend can format it
    secs.to_string()
}

#[tauri::command]
pub fn load_profiles(app: tauri::AppHandle) -> Result<ProfilesConfig, String> {
    let path = get_profiles_path(&app)?;

    if !path.exists() {
        let config = make_default_config();
        let json =
            serde_json::to_string_pretty(&config).map_err(|e| format!("JSON error: {}", e))?;

        // Ensure parent dir exists
        if let Some(parent) = path.parent() {
            fs::create_dir_all(parent)
                .map_err(|e| format!("Cannot create app data dir: {}", e))?;
        }

        fs::write(&path, json).map_err(|e| format!("Cannot write profiles.json: {}", e))?;
        return Ok(config);
    }

    let content =
        fs::read_to_string(&path).map_err(|e| format!("Cannot read profiles.json: {}", e))?;
    let config: ProfilesConfig =
        serde_json::from_str(&content).map_err(|e| format!("Invalid profiles.json: {}", e))?;
    Ok(config)
}

#[tauri::command]
pub fn save_profiles(app: tauri::AppHandle, config: ProfilesConfig) -> Result<(), String> {
    let path = get_profiles_path(&app)?;
    let json =
        serde_json::to_string_pretty(&config).map_err(|e| format!("JSON error: {}", e))?;
    fs::write(&path, json).map_err(|e| format!("Cannot write profiles.json: {}", e))
}

/// Delete a secondary profile's database, with its SQLite side files and the
/// copies a catch-up took (#390): the guide promises that deleting a profile
/// deletes all its data.
#[tauri::command]
pub fn delete_profile_db(app: tauri::AppHandle, db_filename: String) -> Result<(), String> {
    if db_filename == database::DEFAULT_PROFILE_DB {
        return Err("Cannot delete the default profile database".to_string());
    }
    let db_path = profile_db_path(&app, &db_filename)?;
    delete_profile_files(&db_path, &db_filename)
}

fn delete_profile_files(db_path: &Path, db_filename: &str) -> Result<(), String> {
    for suffix in ["", "-wal", "-shm", "-journal"] {
        let path = db_path.with_file_name(format!("{}{}", db_filename, suffix));
        if path.exists() {
            fs::remove_file(&path).map_err(|e| format!("Cannot delete database file: {}", e))?;
        }
    }
    if let Some(dir) = db_path.parent() {
        profile_db::remove_backups(
            &dir.join(profile_db::MIGRATION_BACKUP_DIR),
            db_filename.trim_end_matches(".db"),
            None,
        )?;
    }
    Ok(())
}

/// SQL that creates a secondary profile, run by the webview through the
/// plugin (`initializeNewProfileDb`).
#[tauri::command]
pub fn get_new_profile_init_sql() -> Result<Vec<String>, String> {
    // The consolidated schema is the whole database: tauri-plugin-sql runs no
    // migration for a `profile_<id>.db`, only the default profile's URL is
    // registered (lib.rs). It carries the v1 IPC-aligned taxonomy (categories,
    // keywords, categories_schema_version='v1'). The second statement writes
    // the complete migration history, so later versions reach the profile
    // through `prepare_profile_db` without inferring anything (#390).
    Ok(vec![
        database::CONSOLIDATED_SCHEMA.to_string(),
        profile_db::history_sql(&crate::migrations()),
    ])
}

/// Bring a profile database up to date and repair legacy values before the
/// webview opens it (#390, ADR 0021). Secondary profiles catch up on the
/// migrations they missed; every profile gets its text manual-categorization
/// flags repaired. Sync on purpose: Tauri runs sync commands on the main
/// thread, which serializes two opens of the same profile (React StrictMode
/// mounts twice in development).
#[tauri::command]
pub fn prepare_profile_db(
    app: tauri::AppHandle,
    db_filename: String,
) -> Result<profile_db::ProfilePreparation, String> {
    let db_path = profile_db_path(&app, &db_filename)?;
    profile_db::prepare_at(&db_path, &db_filename, &crate::migrations())
}

// Argon2id parameters for PIN hashing (same as export_import_commands.rs)
const ARGON2_M_COST: u32 = 65536; // 64 MiB
const ARGON2_T_COST: u32 = 3;
const ARGON2_P_COST: u32 = 1;
const ARGON2_OUTPUT_LEN: usize = 32;
const ARGON2_SALT_LEN: usize = 16;

fn argon2_hash(pin: &str, salt: &[u8]) -> Result<Vec<u8>, String> {
    let params = Params::new(ARGON2_M_COST, ARGON2_T_COST, ARGON2_P_COST, Some(ARGON2_OUTPUT_LEN))
        .map_err(|e| format!("Argon2 params error: {}", e))?;
    let argon2 = Argon2::new(Algorithm::Argon2id, Version::V0x13, params);
    let mut hash = vec![0u8; ARGON2_OUTPUT_LEN];
    argon2
        .hash_password_into(pin.as_bytes(), salt, &mut hash)
        .map_err(|e| format!("Argon2 hash error: {}", e))?;
    Ok(hash)
}

#[tauri::command]
pub fn hash_pin(pin: String) -> Result<String, String> {
    let mut salt = [0u8; ARGON2_SALT_LEN];
    rand::rngs::OsRng.fill_bytes(&mut salt);
    let salt_hex = hex_encode(&salt);

    let hash = argon2_hash(&pin, &salt)?;
    let hash_hex = hex_encode(&hash);

    // Store as "argon2id:salt:hash" to distinguish from legacy SHA-256 "salt:hash"
    Ok(format!("argon2id:{}:{}", salt_hex, hash_hex))
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct VerifyPinResult {
    pub valid: bool,
    /// New Argon2id hash when a legacy SHA-256 PIN was successfully verified and re-hashed
    pub rehashed: Option<String>,
}

#[tauri::command]
pub fn verify_pin(pin: String, stored_hash: String) -> Result<VerifyPinResult, String> {
    // Argon2id format: "argon2id:salt_hex:hash_hex"
    if let Some(rest) = stored_hash.strip_prefix("argon2id:") {
        let parts: Vec<&str> = rest.split(':').collect();
        if parts.len() != 2 {
            return Err("Invalid Argon2id hash format".to_string());
        }
        let salt = hex_decode(parts[0])?;
        let expected_hash = hex_decode(parts[1])?;

        let computed = argon2_hash(&pin, &salt)?;

        let valid = computed.ct_eq(&expected_hash).into();
        return Ok(VerifyPinResult { valid, rehashed: None });
    }

    // Legacy SHA-256 format: "salt_hex:hash_hex"
    let parts: Vec<&str> = stored_hash.split(':').collect();
    if parts.len() != 2 {
        return Err("Invalid stored hash format".to_string());
    }
    let salt_hex = parts[0];
    let expected_hash = hex_decode(parts[1])?;

    let mut hasher = Sha256::new();
    hasher.update(salt_hex.as_bytes());
    hasher.update(pin.as_bytes());
    let result = hasher.finalize();

    let valid: bool = result.as_slice().ct_eq(&expected_hash).into();

    if valid {
        // Re-hash with Argon2id so this legacy PIN is upgraded.
        // If rehash fails, still allow login — don't block the user.
        let rehashed = hash_pin(pin).ok();
        Ok(VerifyPinResult { valid: true, rehashed })
    } else {
        Ok(VerifyPinResult { valid: false, rehashed: None })
    }
}

fn hex_encode(bytes: &[u8]) -> String {
    bytes.iter().map(|b| format!("{:02x}", b)).collect()
}

fn hex_decode(hex: &str) -> Result<Vec<u8>, String> {
    if !hex.len().is_multiple_of(2) {
        return Err("Invalid hex string length".to_string());
    }
    (0..hex.len())
        .step_by(2)
        .map(|i| {
            u8::from_str_radix(&hex[i..i + 2], 16)
                .map_err(|e| format!("Invalid hex character: {}", e))
        })
        .collect()
}

/// Repair migration checksums for a profile database.
/// Updates stored checksums to match current migration SQL, avoiding re-application
/// of destructive migrations (e.g., migration 2 which DELETEs categories/keywords).
#[tauri::command]
pub fn repair_migrations(app: tauri::AppHandle, db_filename: String) -> Result<bool, String> {
    let db_path = profile_db_path(&app, &db_filename)?;

    if !db_path.exists() {
        return Ok(false);
    }

    let conn = rusqlite::Connection::open(&db_path)
        .map_err(|e| format!("Cannot open database: {}", e))?;

    let table_exists: bool = conn
        .query_row(
            "SELECT COUNT(*) > 0 FROM sqlite_master WHERE type='table' AND name='_sqlx_migrations'",
            [],
            |row| row.get(0),
        )
        .unwrap_or(false);

    if !table_exists {
        return Ok(false);
    }

    // Current migration SQL — must match the vec in lib.rs
    let migrations: &[(i64, &str)] = &[
        (1, database::SCHEMA),
        (2, database::SEED_CATEGORIES),
    ];

    let mut repaired = false;
    for (version, sql) in migrations {
        let expected_checksum = Sha384::digest(sql.as_bytes()).to_vec();

        // Check if this migration exists with a different checksum
        let needs_repair: bool = conn
            .query_row(
                "SELECT COUNT(*) > 0 FROM _sqlx_migrations WHERE version = ?1 AND checksum != ?2",
                rusqlite::params![version, expected_checksum],
                |row| row.get(0),
            )
            .unwrap_or(false);

        if needs_repair {
            conn.execute(
                "UPDATE _sqlx_migrations SET checksum = ?1 WHERE version = ?2",
                rusqlite::params![expected_checksum, version],
            )
            .map_err(|e| format!("Cannot repair migration {}: {}", version, e))?;
            repaired = true;
        }
    }

    Ok(repaired)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_hash_pin_produces_argon2id_format() {
        let hash = hash_pin("1234".to_string()).unwrap();
        assert!(hash.starts_with("argon2id:"), "Hash should start with 'argon2id:' prefix");
        let parts: Vec<&str> = hash.split(':').collect();
        assert_eq!(parts.len(), 3, "Hash should have 3 parts: prefix:salt:hash");
        assert_eq!(parts[1].len(), ARGON2_SALT_LEN * 2, "Salt should be {} hex chars", ARGON2_SALT_LEN * 2);
        assert_eq!(parts[2].len(), ARGON2_OUTPUT_LEN * 2, "Hash should be {} hex chars", ARGON2_OUTPUT_LEN * 2);
    }

    #[test]
    fn test_hash_pin_different_salts() {
        let h1 = hash_pin("1234".to_string()).unwrap();
        let h2 = hash_pin("1234".to_string()).unwrap();
        assert_ne!(h1, h2, "Two hashes of the same PIN should use different salts");
    }

    #[test]
    fn test_verify_argon2id_pin_correct() {
        let hash = hash_pin("5678".to_string()).unwrap();
        let result = verify_pin("5678".to_string(), hash).unwrap();
        assert!(result.valid, "Correct PIN should verify");
        assert!(result.rehashed.is_none(), "Argon2id PIN should not be rehashed");
    }

    #[test]
    fn test_verify_argon2id_pin_wrong() {
        let hash = hash_pin("5678".to_string()).unwrap();
        let result = verify_pin("0000".to_string(), hash).unwrap();
        assert!(!result.valid, "Wrong PIN should not verify");
        assert!(result.rehashed.is_none());
    }

    #[test]
    fn test_verify_legacy_sha256_correct_and_rehash() {
        // Create a legacy SHA-256 hash: "salt_hex:sha256(salt_hex + pin)"
        let salt_hex = "abcdef0123456789";
        let mut hasher = Sha256::new();
        hasher.update(salt_hex.as_bytes());
        hasher.update(b"4321");
        let hash_bytes = hasher.finalize();
        let hash_hex = hex_encode(&hash_bytes);
        let stored = format!("{}:{}", salt_hex, hash_hex);

        let result = verify_pin("4321".to_string(), stored).unwrap();
        assert!(result.valid, "Correct legacy PIN should verify");
        assert!(result.rehashed.is_some(), "Legacy PIN should be rehashed to Argon2id");

        // Verify the rehashed value is a valid Argon2id hash
        let new_hash = result.rehashed.unwrap();
        assert!(new_hash.starts_with("argon2id:"));

        // Verify the rehashed value works for future verification
        let result2 = verify_pin("4321".to_string(), new_hash).unwrap();
        assert!(result2.valid, "Rehashed PIN should verify");
        assert!(result2.rehashed.is_none(), "Already Argon2id, no rehash needed");
    }

    #[test]
    fn test_verify_legacy_sha256_wrong() {
        let salt_hex = "abcdef0123456789";
        let mut hasher = Sha256::new();
        hasher.update(salt_hex.as_bytes());
        hasher.update(b"4321");
        let hash_bytes = hasher.finalize();
        let hash_hex = hex_encode(&hash_bytes);
        let stored = format!("{}:{}", salt_hex, hash_hex);

        let result = verify_pin("9999".to_string(), stored).unwrap();
        assert!(!result.valid, "Wrong legacy PIN should not verify");
        assert!(result.rehashed.is_none(), "Failed verification should not rehash");
    }

    #[test]
    fn test_verify_invalid_format() {
        let result = verify_pin("1234".to_string(), "invalid".to_string());
        assert!(result.is_err(), "Single-part hash should fail");

        let result = verify_pin("1234".to_string(), "argon2id:bad".to_string());
        assert!(result.is_err(), "Argon2id with wrong part count should fail");
    }

    #[test]
    fn test_hex_roundtrip() {
        let original = vec![0u8, 127, 255, 1, 16];
        let encoded = hex_encode(&original);
        let decoded = hex_decode(&encoded).unwrap();
        assert_eq!(original, decoded);
    }

    // -- profile database location (#390) ------------------------------------

    #[test]
    fn profile_databases_live_where_the_sql_plugin_opens_them() {
        // tauri-plugin-sql resolves `sqlite:<file>` under app_config_dir().
        // On Linux (the CI platform) that differs from app_data_dir(), so
        // going back to the data folder turns this red.
        let app = tauri::test::mock_app();
        let path = profile_db_path(app.handle(), "profile_0a1b2c3d.db").unwrap();
        assert_eq!(path.parent(), Some(app.path().app_config_dir().unwrap().as_path()));
    }

    #[test]
    fn profile_db_path_accepts_the_two_shapes_the_app_uses() {
        let dir = Path::new("/profiles");
        assert_eq!(
            profile_db_path_in(dir, "simpl_resultat.db"),
            Ok(dir.join("simpl_resultat.db"))
        );
        assert_eq!(
            profile_db_path_in(dir, "profile_0a1b2c3d.db"),
            Ok(dir.join("profile_0a1b2c3d.db"))
        );
    }

    #[test]
    fn profile_db_path_refuses_anything_else() {
        let dir = Path::new("/profiles");
        for name in [
            "",
            "/etc/passwd",
            "../simpl_resultat.db",
            "profile_.db",
            "profile_0a1b/../x.db",
            "profile_0a1b2c3d.sqlite",
            "profile_0a1b2c3d.db.bak",
            "PROFILE_0a1b2c3d.db",
            "profile_xyz.db",
            "C:\\Users\\x\\profile_0a1b2c3d.db",
        ] {
            assert_eq!(
                profile_db_path_in(dir, name),
                Err("invalid_profile_db_filename".to_string()),
                "{:?}",
                name
            );
        }
    }

    #[test]
    fn deleting_a_profile_removes_its_files_and_only_its_files() {
        let dir = profile_db::TestDir::new("delete");
        let backups = dir.join(profile_db::MIGRATION_BACKUP_DIR);
        fs::create_dir_all(&backups).unwrap();
        for name in [
            "profile_0a1b2c3d.db",
            // The only side file this app produces: sqlx leaves SQLite's
            // rollback journal by default, `-wal`/`-shm` come with WAL.
            "profile_0a1b2c3d.db-journal",
            "profile_0a1b2c3d.db-wal",
            "profile_0a1b2c3d.db-shm",
            "profile_99999999.db",
        ] {
            fs::write(dir.join(name), b"x").unwrap();
        }
        for name in ["profile_0a1b2c3d-before-v7.db", "profile_99999999-before-v17.db"] {
            fs::write(backups.join(name), b"x").unwrap();
        }

        delete_profile_files(&dir.join("profile_0a1b2c3d.db"), "profile_0a1b2c3d.db").unwrap();

        let mut left: Vec<String> = fs::read_dir(&dir)
            .unwrap()
            .chain(fs::read_dir(&backups).unwrap())
            .map(|e| e.unwrap().file_name().into_string().unwrap())
            .collect();
        left.sort();
        assert_eq!(
            left,
            vec![
                "migration-backups".to_string(),
                "profile_99999999-before-v17.db".to_string(),
                "profile_99999999.db".to_string(),
            ]
        );
    }
}