import { existsSync, readdirSync, readFileSync } from 'fs';
import { join } from 'path';
import { PrismaClient } from '@prisma/client';

const TRACKING_TABLE = '_goldbank_migrations';

/**
 * Applies the .sql files in prisma/migrations (copied to ./migrations in the
 * Docker release) and records them so each one runs once.
 *
 * The deploy image is copy-only and has no Prisma CLI, so `migrate deploy` is
 * not an option — this runs the same SQL through the client instead.
 */
export type MigrationResult = {
  /** True when the tracking table was created by this run (empty database). */
  freshDatabase: boolean;
  applied: string[];
};

function resolveMigrationsDir(): string {
  const candidates = [
    process.env.MIGRATIONS_DIR,
    join(process.cwd(), 'migrations'),
    join(__dirname, '..', '..', 'migrations'),
    join(__dirname, '..', '..', 'prisma', 'migrations'),
    join(process.cwd(), 'prisma', 'migrations'),
  ].filter((p): p is string => Boolean(p));

  const found = candidates.find((dir) => existsSync(dir));
  if (!found) {
    throw new Error(
      `پوشه migrations پیدا نشد. مسیرهای بررسی‌شده: ${candidates.join(', ')}`,
    );
  }
  return found;
}

/**
 * Postgres rejects multiple statements in one parameterised query, so each file
 * is split first. Quoting rules matter: identifiers/strings may contain ';'.
 */
export function splitSqlStatements(sql: string): string[] {
  const statements: string[] = [];
  let current = '';
  let i = 0;

  while (i < sql.length) {
    const char = sql[i];
    const rest = sql.slice(i);

    if (rest.startsWith('--')) {
      const lineEnd = sql.indexOf('\n', i);
      i = lineEnd === -1 ? sql.length : lineEnd + 1;
      continue;
    }
    if (rest.startsWith('/*')) {
      const commentEnd = sql.indexOf('*/', i + 2);
      i = commentEnd === -1 ? sql.length : commentEnd + 2;
      continue;
    }

    if (char === "'" || char === '"') {
      const quote = char;
      current += char;
      i += 1;
      while (i < sql.length) {
        current += sql[i];
        if (sql[i] === quote) {
          // Doubled quote is an escaped quote, not the end of the literal.
          if (sql[i + 1] === quote) {
            current += sql[i + 1];
            i += 2;
            continue;
          }
          i += 1;
          break;
        }
        i += 1;
      }
      continue;
    }

    const dollarTag = /^\$[A-Za-z_]*\$/.exec(rest);
    if (dollarTag) {
      const tag = dollarTag[0];
      const closing = sql.indexOf(tag, i + tag.length);
      const end = closing === -1 ? sql.length : closing + tag.length;
      current += sql.slice(i, end);
      i = end;
      continue;
    }

    if (char === ';') {
      if (current.trim()) statements.push(current.trim());
      current = '';
      i += 1;
      continue;
    }

    current += char;
    i += 1;
  }

  if (current.trim()) statements.push(current.trim());
  return statements;
}

export async function runMigrations(prisma: PrismaClient): Promise<MigrationResult> {
  const dir = resolveMigrationsDir();
  const files = readdirSync(dir)
    .filter((name) => name.endsWith('.sql'))
    .sort();

  const trackingExisted = await prisma.$queryRawUnsafe<{ exists: boolean }[]>(
    `SELECT EXISTS (
       SELECT 1 FROM information_schema.tables
       WHERE table_schema = current_schema() AND table_name = $1
     ) AS "exists"`,
    TRACKING_TABLE,
  );
  const freshDatabase = !trackingExisted[0]?.exists;

  await prisma.$executeRawUnsafe(
    `CREATE TABLE IF NOT EXISTS "${TRACKING_TABLE}" (
       name TEXT PRIMARY KEY,
       applied_at TIMESTAMPTZ NOT NULL DEFAULT now()
     )`,
  );

  const alreadyApplied = await prisma.$queryRawUnsafe<{ name: string }[]>(
    `SELECT name FROM "${TRACKING_TABLE}"`,
  );
  const appliedNames = new Set(alreadyApplied.map((row) => row.name));

  const applied: string[] = [];
  for (const file of files) {
    if (appliedNames.has(file)) continue;

    const statements = splitSqlStatements(readFileSync(join(dir, file), 'utf8'));
    await prisma.$transaction(
      async (tx) => {
        for (const statement of statements) {
          await tx.$executeRawUnsafe(statement);
        }
        await tx.$executeRawUnsafe(
          `INSERT INTO "${TRACKING_TABLE}" (name) VALUES ($1)`,
          file,
        );
      },
      // The baseline migration is hundreds of DDL statements; the 5s default is
      // not enough, especially against a remote database.
      { maxWait: 60_000, timeout: 600_000 },
    );
    applied.push(file);
  }

  return { freshDatabase, applied };
}

/** Records a one-off task (e.g. seeding) in the same table so it never repeats. */
export async function runOnce(
  prisma: PrismaClient,
  name: string,
  task: () => Promise<void>,
): Promise<boolean> {
  const rows = await prisma.$queryRawUnsafe<{ name: string }[]>(
    `SELECT name FROM "${TRACKING_TABLE}" WHERE name = $1`,
    name,
  );
  if (rows.length > 0) return false;

  await task();
  await prisma.$executeRawUnsafe(
    `INSERT INTO "${TRACKING_TABLE}" (name) VALUES ($1)`,
    name,
  );
  return true;
}