import { createHash } from 'node:crypto';
import { readFile } from 'node:fs/promises';
import { dirname, resolve } from 'node:path';
import { fileURLToPath } from 'node:url';
import type { MySqlPool } from './mysql.js';

export type MigrationDirection = 'up' | 'verify' | 'down';

export interface MigrationPlan {
  direction: MigrationDirection;
  file: string;
  checksum: string;
  statements: readonly string[];
}

export interface MigrationExecutionResult extends MigrationPlan {
  executed: boolean;
  affectedRows: number;
}

const repoRoot = resolve(dirname(fileURLToPath(import.meta.url)), '../../..');
const migrationFiles: Record<MigrationDirection, readonly string[]> = {
  up: [
    'database/migrations/2026061601_m01b_core_schema.up.sql',
    'database/migrations/2026061802_m01c_async_tasks.up.sql',
    'database/migrations/2026061803_m02a_tenant_apps.up.sql',
    'database/migrations/2026061804_m02b_wechat_auth.up.sql',
    'database/migrations/2026061805_m02c_rbac.up.sql',
    'database/migrations/2026061806_m02d_user_management.up.sql',
    'database/migrations/2026061807_m03a_store_room_domain.up.sql',
    'database/migrations/2026061808_m03b_decoration_ads_media.up.sql',
    'database/migrations/2026061809_m03c_store_discovery.up.sql',
    'database/migrations/2026061810_m03d_scene_wifi_access.up.sql',
    'database/migrations/2026061811_m04a_pricing_reservations.up.sql',
    'database/migrations/2026062012_m04b_order_state_machine.up.sql',
    'database/migrations/2026062013_m04c_order_adjustments.up.sql'
  ],
  verify: [
    'database/migrations/2026061601_m01b_core_schema.verify.sql',
    'database/migrations/2026061802_m01c_async_tasks.verify.sql',
    'database/migrations/2026061803_m02a_tenant_apps.verify.sql',
    'database/migrations/2026061804_m02b_wechat_auth.verify.sql',
    'database/migrations/2026061805_m02c_rbac.verify.sql',
    'database/migrations/2026061806_m02d_user_management.verify.sql',
    'database/migrations/2026061807_m03a_store_room_domain.verify.sql',
    'database/migrations/2026061808_m03b_decoration_ads_media.verify.sql',
    'database/migrations/2026061809_m03c_store_discovery.verify.sql',
    'database/migrations/2026061810_m03d_scene_wifi_access.verify.sql',
    'database/migrations/2026061811_m04a_pricing_reservations.verify.sql',
    'database/migrations/2026062012_m04b_order_state_machine.verify.sql',
    'database/migrations/2026062013_m04c_order_adjustments.verify.sql'
  ],
  down: [
    'database/migrations/2026062013_m04c_order_adjustments.down.sql',
    'database/migrations/2026062012_m04b_order_state_machine.down.sql',
    'database/migrations/2026061811_m04a_pricing_reservations.down.sql',
    'database/migrations/2026061810_m03d_scene_wifi_access.down.sql',
    'database/migrations/2026061809_m03c_store_discovery.down.sql',
    'database/migrations/2026061808_m03b_decoration_ads_media.down.sql',
    'database/migrations/2026061807_m03a_store_room_domain.down.sql',
    'database/migrations/2026061806_m02d_user_management.down.sql',
    'database/migrations/2026061805_m02c_rbac.down.sql',
    'database/migrations/2026061804_m02b_wechat_auth.down.sql',
    'database/migrations/2026061803_m02a_tenant_apps.down.sql',
    'database/migrations/2026061802_m01c_async_tasks.down.sql',
    'database/migrations/2026061601_m01b_core_schema.down.sql'
  ]
};

export function splitSqlStatements(sql: string): string[] {
  const statements: string[] = [];
  let current = '';
  let quote: "'" | '"' | '`' | null = null;
  let escaped = false;
  let lineComment = false;
  let blockComment = false;

  for (let index = 0; index < sql.length; index += 1) {
    const character = sql[index];
    const next = sql[index + 1];

    if (lineComment) {
      if (character === '\n') {
        lineComment = false;
        current += character;
      }
      continue;
    }

    if (blockComment) {
      if (character === '*' && next === '/') {
        blockComment = false;
        index += 1;
      }
      continue;
    }

    if (!quote && character === '-' && next === '-' && (index === 0 || /\s/.test(sql[index - 1]))) {
      lineComment = true;
      index += 1;
      continue;
    }

    if (!quote && character === '/' && next === '*') {
      blockComment = true;
      index += 1;
      continue;
    }

    current += character;

    if (quote) {
      if (escaped) {
        escaped = false;
      } else if (character === '\\') {
        escaped = true;
      } else if (character === quote) {
        if (next === quote) {
          current += next;
          index += 1;
        } else {
          quote = null;
        }
      }
      continue;
    }

    if (character === "'" || character === '"' || character === '`') {
      quote = character;
      continue;
    }

    if (character === ';') {
      const statement = current.slice(0, -1).trim();
      if (statement) {
        statements.push(statement);
      }
      current = '';
    }
  }

  const trailing = current.trim();
  if (trailing) {
    statements.push(trailing);
  }

  if (quote || blockComment) {
    throw new Error('Migration SQL contains an unterminated quote or comment.');
  }

  return statements;
}

export async function loadMigrationPlan(direction: MigrationDirection): Promise<MigrationPlan> {
  const relativeFiles = migrationFiles[direction];
  const sqlParts = await Promise.all(
    relativeFiles.map((relativeFile) => readFile(resolve(repoRoot, relativeFile), 'utf8'))
  );
  const sql = sqlParts.join('\n');

  return {
    direction,
    file: relativeFiles.join(','),
    checksum: createHash('sha256').update(sql).digest('hex'),
    statements: splitSqlStatements(sql)
  };
}

export async function executeMigrationPlan(
  pool: Pick<MySqlPool, 'query'>,
  plan: MigrationPlan,
  dryRun = false
): Promise<MigrationExecutionResult> {
  if (dryRun) {
    return { ...plan, executed: false, affectedRows: 0 };
  }

  let affectedRows = 0;
  for (const [index, statement] of plan.statements.entries()) {
    const [result] = await pool.query(statement);
    if (plan.direction === 'verify') {
      const minimumRows = [
        10, 26, 1,
        2, 5, 1,
        3, 5, 1,
        3, 7, 1,
        5, 3, 7, 1,
        1, 3, 1,
        3, 6, 13, 1,
        3, 3, 1,
        2, 2, 1,
        3, 3, 1,
        2, 1, 3, 3, 1,
        2, 1, 3, 1,
        2, 2, 1, 2, 1
      ][index] ?? 1;
      if (!Array.isArray(result) || result.length < minimumRows) {
        throw new Error(
          `Migration verification statement ${index + 1} returned fewer than ${minimumRows} rows.`
        );
      }
    }
    if (result && typeof result === 'object' && 'affectedRows' in result) {
      const value = Reflect.get(result, 'affectedRows');
      if (typeof value === 'number') {
        affectedRows += value;
      }
    }
  }

  return { ...plan, executed: true, affectedRows };
}