import { randomInt } from 'node:crypto';
import fs from 'node:fs/promises';
import path from 'node:path';
import { drizzle, type SQLJsDatabase } from 'drizzle-orm/sql-js';
import initSqlJs, { type Database as RawSqlJsDatabase } from 'sql.js';
import { loadAirportsGeoJson } from '@/lib/airports';
import { buildSeed, mulberry32 } from '@/lib/game/seed';
import * as schema from './schema';

// SQLite via sql.js (WASM) — no native compilation, so it builds and runs in the
// alpine Docker image without a toolchain. Trade-off: the DB lives in memory and
// every write must be exported to disk; persist() does that atomically (tmp file
// + rename) and is called after each mutation.

export interface GameDb {
  db: SQLJsDatabase<typeof schema>;
  raw: RawSqlJsDatabase;
  file: string;
}

// CREATE TABLE statements mirroring lib/db/schema.ts — keep in sync.
const DDL = `
CREATE TABLE IF NOT EXISTS planes (
  id TEXT PRIMARY KEY NOT NULL,
  model TEXT NOT NULL,
  status TEXT NOT NULL,
  fuel REAL NOT NULL,
  max_fuel REAL NOT NULL,
  location_icao TEXT NOT NULL,
  dest_icao TEXT,
  lat REAL NOT NULL,
  lon REAL NOT NULL,
  departure_sim_time INTEGER,
  queue TEXT NOT NULL DEFAULT '[]',
  health REAL NOT NULL DEFAULT 100,
  repair_until_sim_time INTEGER
);
CREATE TABLE IF NOT EXISTS packages (
  id TEXT PRIMARY KEY NOT NULL,
  origin_icao TEXT NOT NULL,
  dest_icao TEXT NOT NULL,
  reward REAL NOT NULL,
  cargo_type TEXT NOT NULL,
  cargo_count INTEGER NOT NULL,
  weight_kg REAL NOT NULL DEFAULT 2000,
  special TEXT,
  deadline_sim_time INTEGER NOT NULL,
  status TEXT NOT NULL,
  plane_id TEXT,
  created_sim_time INTEGER NOT NULL,
  created_real_ms INTEGER NOT NULL DEFAULT 0,
  slot_free_at_real_ms INTEGER
);
CREATE TABLE IF NOT EXISTS account (
  cash REAL NOT NULL,
  reputation REAL NOT NULL
);
CREATE TABLE IF NOT EXISTS sim_state (
  clock_ms INTEGER NOT NULL,
  time_scale REAL NOT NULL,
  paused INTEGER NOT NULL,
  last_real_tick_ms INTEGER NOT NULL DEFAULT 0,
  last_selected_time_scale REAL NOT NULL DEFAULT 1
);
`;

// v0.7.0: DBs created by earlier versions lack the new columns; CREATE TABLE IF
// NOT EXISTS won't add them, so ALTER (guarded by PRAGMA table_info). Fresh DBs
// already have everything from DDL above and this is a no-op for them.
function migrateColumns(raw: RawSqlJsDatabase): void {
  const cols = (table: string): Set<string> =>
    new Set(raw.exec(`PRAGMA table_info(${table})`)[0].values.map((r) => String(r[1])));
  if (!cols('sim_state').has('last_real_tick_ms')) {
    raw.exec('ALTER TABLE sim_state ADD COLUMN last_real_tick_ms INTEGER NOT NULL DEFAULT 0');
  }
  if (!cols('planes').has('departure_sim_time')) {
    raw.exec('ALTER TABLE planes ADD COLUMN departure_sim_time INTEGER');
  }
  // v0.12.0: the flight destination column (set by fly, cleared on arrival).
  if (!cols('planes').has('dest_icao')) {
    raw.exec('ALTER TABLE planes ADD COLUMN dest_icao TEXT');
  }
  // v0.25.0 (ISS-043): the flight queue — ordered JSON array of not-yet-started leg ICACs.
  if (!cols('planes').has('queue')) {
    raw.exec(`ALTER TABLE planes ADD COLUMN queue TEXT NOT NULL DEFAULT '[]'`);
  }
  // v0.27.0 (ISS-045): package weight — pre-existing rows backfill to a mid-range default.
  if (!cols('packages').has('weight_kg')) {
    raw.exec('ALTER TABLE packages ADD COLUMN weight_kg REAL NOT NULL DEFAULT 2000');
  }
  // v0.37.0 (ISS-073): package special status — nullable, no default; pre-existing rows stay NULL = none.
  if (!cols('packages').has('special')) {
    raw.exec('ALTER TABLE packages ADD COLUMN special TEXT');
  }
  // v0.39.0 (ISS-069): plane health — pre-existing rows backfill to full health.
  if (!cols('planes').has('health')) {
    raw.exec('ALTER TABLE planes ADD COLUMN health REAL NOT NULL DEFAULT 100');
  }
  // v0.39.0 (ISS-069): repair gate — nullable, no default; pre-existing rows stay NULL = not in repair.
  if (!cols('planes').has('repair_until_sim_time')) {
    raw.exec('ALTER TABLE planes ADD COLUMN repair_until_sim_time INTEGER');
  }
  // v0.65.0: real-time creation stamp — legacy rows backfill to NOW so they get a fresh full lifetime
  // instead of expiring on the first tick (created_real_ms = 0 is far in the past).
  if (!cols('packages').has('created_real_ms')) {
    raw.exec(`ALTER TABLE packages ADD COLUMN created_real_ms INTEGER NOT NULL DEFAULT ${Date.now()}`);
  }
  // v0.65.0: per-(origin, band) refill cooldown — nullable; legacy rows stay NULL = no cooldown.
  if (!cols('packages').has('slot_free_at_real_ms')) {
    raw.exec('ALTER TABLE packages ADD COLUMN slot_free_at_real_ms INTEGER');
  }
  // v0.30.0 (ISS-057): last-selected speed — pre-existing rows backfill to the row's OWN
  // current time_scale so a legacy DB resumes at the speed it was running, not the default.
  if (!cols('sim_state').has('last_selected_time_scale')) {
    raw.exec('ALTER TABLE sim_state ADD COLUMN last_selected_time_scale REAL NOT NULL DEFAULT 1');
    raw.exec('UPDATE sim_state SET last_selected_time_scale = time_scale');
  }
}

// v0.12.0 one-time migration: contracts world → packages world. Detected by the
// presence of the old `contracts` table (fresh and already-migrated DBs never
// have it, so this runs exactly once per file). Preserves account/sim_state rows
// and every plane row; planes are reset to GROUNDED at their locationIcao with
// departure_sim_time/dest_icao cleared — an in-flight plane from the old state
// simply lands back where it took off. Old contract data is wiped (the packages
// table starts empty and the engine's spawn rules reseed the market on the next
// tick). The orphaned pre-v0.12.0 `contract_id` column is dropped too (SQLite
// ≥3.35 DROP COLUMN; guarded so a failure can never block startup).
function migrateContractsToPackages(raw: RawSqlJsDatabase): void {
  const cols = new Set(
    raw.exec('PRAGMA table_info(planes)')[0].values.map((r) => String(r[1])),
  );
  raw.exec(
    `UPDATE planes SET status = 'available', departure_sim_time = NULL, dest_icao = NULL` +
      (cols.has('contract_id') ? ', contract_id = NULL' : ''),
  );
  if (cols.has('contract_id')) {
    try {
      raw.exec('ALTER TABLE planes DROP COLUMN contract_id');
    } catch {
      // Leaving the orphaned column is harmless — nothing references it anymore.
    }
  }
  raw.exec('DROP TABLE contracts');
}

// FLIGHT_DB_PATH override exists so unit tests can point at a temp file instead
// of the real ./db/flight.db.
export function defaultDbPath(): string {
  return process.env.FLIGHT_DB_PATH ?? path.join(process.cwd(), 'db', 'flight.db');
}

async function open(file: string): Promise<GameDb> {
  const SQL = await initSqlJs();
  let bytes: Buffer | undefined;
  try {
    bytes = await fs.readFile(file);
  } catch (err) {
    if ((err as NodeJS.ErrnoException).code !== 'ENOENT') throw err;
  }
  const raw = bytes ? new SQL.Database(new Uint8Array(bytes)) : new SQL.Database();
  raw.exec(DDL); // no-op for tables that already exist in an older file
  migrateColumns(raw);

  // v0.12.0: run BEFORE the seed check — a pre-v0.12.0 file has account rows, so
  // without this it would keep the dead contracts table forever.
  const tables = new Set(
    raw.exec("SELECT name FROM sqlite_master WHERE type='table'")[0].values.map((r) => String(r[0])),
  );
  if (tables.has('contracts')) {
    migrateContractsToPackages(raw);
  }

  const instance: GameDb = { db: drizzle(raw, { schema }), raw, file };

  // First-run seed: only when the DB is empty (no account row yet).
  const res = raw.exec('SELECT COUNT(*) FROM account');
  if (Number(res[0]?.values?.[0]?.[0] ?? 0) === 0) {
    console.warn(`flight db: no existing world at ${file} — seeding a fresh one`);
    await seedEmpty(instance);
  }

  // v0.7.0 fixup: pre-v0.7.0 DBs got last_real_tick_ms = 0 from the ALTER TABLE
  // default. Reset it to "now" so the first tick-on-read resumes cleanly instead
  // of taking one clamped catch-up jump. Fresh seeds already carry a real value.
  const simRows = raw.exec('SELECT clock_ms, last_real_tick_ms FROM sim_state');
  if (simRows[0]?.values?.length && Number(simRows[0].values[0][1]) === 0) {
    raw.exec(`UPDATE sim_state SET last_real_tick_ms = ${Date.now()}`);
    await persist(instance);
  }
  return instance;
}

async function seedEmpty(instance: GameDb): Promise<void> {
  const fc = await loadAirportsGeoJson();
  const airports = fc.features.map((f) => ({
    icao: f.properties.icao,
    name: f.properties.name,
    lat: f.properties.lat,
    lon: f.properties.lon,
  }));
  // Random per-install seed; tests call buildSeed directly with a fixed RNG.
  const rng = mulberry32(randomInt(0, 2 ** 31));
  const data = buildSeed({ airports, rng, nowMs: Date.now() });

  // SeedPlane.queue is a string[]; the column stores it as JSON text.
  const { queue, ...planeCols } = data.plane;
  await instance.db.insert(schema.planes).values({ ...planeCols, queue: JSON.stringify(queue ?? []) });
  await instance.db.insert(schema.packages).values(data.packages);
  await instance.db.insert(schema.account).values(data.account);
  await instance.db.insert(schema.simState).values(data.simState);
  await persist(instance);
}

// Durably save the in-memory DB: export bytes, write to a temp file, rename over
// the target so a crash mid-write never leaves a truncated DB.
export async function persist(instance: GameDb): Promise<void> {
  const bytes = instance.raw.export();
  await fs.mkdir(path.dirname(instance.file), { recursive: true });
  const tmp = `${instance.file}.tmp`;
  await fs.writeFile(tmp, Buffer.from(bytes));
  await fs.rename(tmp, instance.file);
}

// Singleton for the app process; openGameDb() is the uncached variant (tests). ISS-129 (v0.57.0):
// lives on globalThis because Next.js can load this module more than once per process —
// instrumentation.ts and route handlers get separate module instances, so a plain `let` would give
// each its own in-memory sql.js DB (both persisting to the same file). One world per process.
const g = globalThis as unknown as { __flightGameDb?: Promise<GameDb> };

export function getGameDb(): Promise<GameDb> {
  return (g.__flightGameDb ??= open(defaultDbPath()));
}

export async function openGameDb(file: string): Promise<GameDb> {
  return open(file);
}