import fs from 'node:fs/promises';
import path from 'node:path';
import pg from 'pg';
import {
  defaultPostgresTuningProfile,
  getPostgresTuningProfile,
  getPostgresTuningSettingNames,
} from './lib/postgres-tuning-profile.js';

const databaseUrl = process.env.DATABASE_URL || 'postgresql://postgres:postgres@127.0.0.1:54322/postgres';
const outputDir = process.env.PG_TUNING_OUTPUT_DIR || 'docs/refactor/launch-artifacts';

function parseArgs(argv) {
  const options = {
    profile: process.env.PG_TUNING_PROFILE || defaultPostgresTuningProfile,
    strict: process.env.PG_TUNING_STRICT === 'true',
    printSql: false,
    json: false,
  };
  for (let index = 2; index < argv.length; index += 1) {
    const arg = argv[index];
    if (arg === '--strict') options.strict = true;
    else if (arg === '--json') options.json = true;
    else if (arg === '--print-sql') options.printSql = true;
    else if (arg === '--profile') {
      options.profile = argv[index + 1] || options.profile;
      index += 1;
    } else if (arg.startsWith('--profile=')) {
      options.profile = arg.slice('--profile='.length);
    }
  }
  options.profileDefinition = getPostgresTuningProfile(options.profile);
  options.settingNames = getPostgresTuningSettingNames(options.profile);
  return options;
}

function shanghaiStamp(date = new Date()) {
  const parts = Object.fromEntries(
    new Intl.DateTimeFormat('en-CA', {
      timeZone: 'Asia/Shanghai',
      year: 'numeric',
      month: '2-digit',
      day: '2-digit',
      hour: '2-digit',
      minute: '2-digit',
      second: '2-digit',
      hour12: false,
    }).formatToParts(date).map(part => [part.type, part.value]),
  );
  return `${parts.year}${parts.month}${parts.day}-${parts.hour}${parts.minute}${parts.second}`;
}

async function query(pool, sql, params = []) {
  const result = await pool.query(sql, params);
  return result.rows;
}

async function maybeQuery(pool, sql, params = []) {
  try {
    return await query(pool, sql, params);
  } catch (error) {
    return { unavailable: true, message: error?.message || String(error) };
  }
}

function redactUrl(value) {
  return value.replace(/:\/\/([^:]+):([^@]+)@/, '://$1:[redacted]@');
}

function pgUnitMultiplier(unit) {
  const text = String(unit || '').trim().toLowerCase();
  if (!text) return 1;
  if (text === 'ms') return 1;
  if (text === 's') return 1000;
  if (text === 'min') return 60_000;
  const memoryMatch = text.match(/^(\d+)?\s*(b|kb|mb|gb|tb)$/);
  if (!memoryMatch) return 1;
  const blockCount = Number(memoryMatch[1] || 1);
  const unitName = memoryMatch[2];
  const factors = {
    b: 1,
    kb: 1024,
    mb: 1024 ** 2,
    gb: 1024 ** 3,
    tb: 1024 ** 4,
  };
  return blockCount * factors[unitName];
}

function formatBytes(bytes) {
  if (!Number.isFinite(bytes)) return '';
  const units = ['B', 'KB', 'MB', 'GB', 'TB'];
  let value = bytes;
  let unitIndex = 0;
  while (value >= 1024 && unitIndex < units.length - 1) {
    value /= 1024;
    unitIndex += 1;
  }
  const rounded = value >= 10 || Number.isInteger(value) ? value.toFixed(0) : value.toFixed(1);
  return `${rounded}${units[unitIndex]}`;
}

function formatDuration(ms) {
  if (!Number.isFinite(ms)) return '';
  if (ms === 0) return '0ms';
  if (ms % 60_000 === 0) return `${ms / 60_000}min`;
  if (ms % 1000 === 0) return `${ms / 1000}s`;
  return `${ms}ms`;
}

function normalizedSettingValue(setting) {
  const number = Number(setting.setting);
  if (!Number.isFinite(number)) return `${setting.setting}${setting.unit || ''}`;
  const unit = String(setting.unit || '').trim();
  if (!unit) return String(setting.setting);
  if (/^(?:\d+)?\s*(?:b|kb|mb|gb|tb)$/i.test(unit)) {
    return formatBytes(number * pgUnitMultiplier(unit));
  }
  if (/^(?:ms|s|min)$/i.test(unit)) {
    return formatDuration(number * pgUnitMultiplier(unit));
  }
  return `${setting.setting}${unit}`;
}

function explainSetting(setting) {
  return {
    name: setting.name,
    value: normalizedSettingValue(setting),
    rawSetting: setting.setting,
    unit: setting.unit || null,
    source: setting.source,
    pendingRestart: setting.pending_restart,
  };
}

function parseSettingNumber(setting) {
  if (!setting) return Number.NaN;
  const number = Number(setting.setting);
  return Number.isFinite(number) ? number : Number.NaN;
}

function parseBytes(value) {
  if (typeof value === 'number') return value;
  const text = String(value || '').trim().toLowerCase();
  if (!text) return Number.NaN;
  const match = text.match(/^(-?\d+(?:\.\d+)?)\s*([a-z]+)?$/);
  if (!match) return Number.NaN;
  const amount = Number(match[1]);
  const unit = match[2] || 'b';
  const factors = {
    b: 1,
    byte: 1,
    bytes: 1,
    kb: 1024,
    mb: 1024 ** 2,
    gb: 1024 ** 3,
    tb: 1024 ** 4,
  };
  return amount * (factors[unit] || Number.NaN);
}

function parseDurationMs(value) {
  if (typeof value === 'number') return value;
  const text = String(value || '').trim().toLowerCase();
  if (!text) return Number.NaN;
  const match = text.match(/^(-?\d+(?:\.\d+)?)\s*([a-z]+)?$/);
  if (!match) return Number.NaN;
  const amount = Number(match[1]);
  const unit = match[2] || 'ms';
  const factors = {
    ms: 1,
    s: 1000,
    sec: 1000,
    secs: 1000,
    second: 1000,
    seconds: 1000,
    min: 60_000,
    mins: 60_000,
    minute: 60_000,
    minutes: 60_000,
    h: 3_600_000,
    hour: 3_600_000,
    hours: 3_600_000,
  };
  return amount * (factors[unit] || Number.NaN);
}

function comparableValue(setting, rule) {
  if (!setting) return Number.NaN;
  if (rule.type === 'bytes') return Number(setting.setting) * pgUnitMultiplier(setting.unit);
  if (rule.type === 'duration') return Number(setting.setting) * pgUnitMultiplier(setting.unit);
  return parseSettingNumber(setting);
}

function recommendedComparator(rule, key) {
  if (rule.type === 'bytes') return parseBytes(rule[key]);
  if (rule.type === 'duration') return parseDurationMs(rule[key]);
  return Number(rule[key]);
}

function evaluateProfile(settingsRows, profile) {
  const byName = new Map(settingsRows.map(row => [row.name, row]));
  const failures = [];
  const warnings = [];

  for (const [name, rule] of Object.entries(profile.settings)) {
    const setting = byName.get(name);
    if (!setting) {
      failures.push(`${name} is missing from pg_settings evidence.`);
      continue;
    }
    if (setting.pending_restart) {
      failures.push(`${name} has pending_restart=true; restart PostgreSQL before capacity testing.`);
    }
    if (rule.exact !== undefined) {
      const actual = String(setting.setting || '').toLowerCase();
      if (actual !== String(rule.exact).toLowerCase()) {
        failures.push(`${name} should be ${rule.exact} for ${profile.label}, got ${setting.setting}.`);
      }
      if (String(setting.source || '').toLowerCase() === 'default') {
        warnings.push(`${name} still comes from default; recommended ${profile.name} value is ${rule.recommended}.`);
      }
      continue;
    }
    if (rule.min !== undefined) {
      const actual = comparableValue(setting, rule);
      const expected = recommendedComparator(rule, 'min');
      if (!Number.isFinite(actual) || actual < expected) {
        failures.push(`${name} is below ${rule.min} for ${profile.label}; current value is ${normalizedSettingValue(setting)}.`);
      }
    }
    if (rule.max !== undefined) {
      const actual = comparableValue(setting, rule);
      const expected = recommendedComparator(rule, 'max');
      if (!Number.isFinite(actual) || actual > expected) {
        failures.push(`${name} is above ${rule.max} for ${profile.label}; current value is ${normalizedSettingValue(setting)}.`);
      }
    }
    if (rule.recommended !== undefined && String(setting.source || '').toLowerCase() === 'default') {
      warnings.push(`${name} still comes from default; recommended ${profile.name} value is ${rule.recommended}.`);
    }
  }

  return { failures, warnings };
}

function evaluate(settingsRows, profile, options, pgStatStatements) {
  const byName = new Map(settingsRows.map(row => [row.name, row]));
  const warnings = [];
  const failures = [];
  const maxConnections = Number(byName.get('max_connections')?.setting || 0);
  const jit = String(byName.get('jit')?.setting || '').toLowerCase();
  const statementTimeout = String(byName.get('statement_timeout')?.setting || '');
  const idleTimeout = String(byName.get('idle_in_transaction_session_timeout')?.setting || '');
  const lockTimeout = String(byName.get('lock_timeout')?.setting || '');

  if (maxConnections > 150) warnings.push('max_connections is high for a 4 vCPU database; prefer API/pooler limits over direct connections.');
  if (jit === 'on') warnings.push('jit is on; short OLTP-style question-bank API queries usually start safer with jit=off.');
  if (statementTimeout === '0') warnings.push('statement_timeout is disabled; production API should have a bounded global timeout and import jobs should override per session.');
  if (idleTimeout === '0') warnings.push('idle_in_transaction_session_timeout is disabled; long idle transactions can block migrations and writes.');
  if (lockTimeout === '0') warnings.push('lock_timeout is disabled; ordinary API requests may wait too long behind locks.');
  if (settingsRows.some(row => row.pending_restart)) warnings.push('Some PostgreSQL settings have pending_restart=true; restart is required before capacity testing.');
  if (pgStatStatements?.unavailable) warnings.push('pg_stat_statements is unavailable; enable it before production capacity acceptance.');

  const profileEvaluation = evaluateProfile(settingsRows, profile);
  warnings.push(...profileEvaluation.warnings);
  if (options.strict) {
    failures.push(...profileEvaluation.failures);
    if (pgStatStatements?.unavailable) failures.push('pg_stat_statements is unavailable in strict mode.');
  }

  return {
    status: failures.length ? 'fail' : options.strict ? 'pass' : warnings.length ? 'warn' : 'pass',
    profile: profile.name,
    failures,
    warnings,
  };
}

function markdown(report) {
  const lines = [
    '# PostgreSQL 调参与运行证据',
    '',
    `生成时间：${new Date(report.generatedAt).toLocaleString('zh-CN', { timeZone: 'Asia/Shanghai' })}`,
    '',
    `数据库：${report.databaseUrl}`,
    '',
    `调参 profile：${report.profile.label} (${report.profile.name})`,
    '',
    `评估：${report.evaluation.status}`,
    '',
  ];
  if (report.evaluation.failures.length) {
    lines.push('## 阻断项');
    lines.push('');
    for (const failure of report.evaluation.failures) lines.push(`- ${failure}`);
    lines.push('');
  }
  if (report.evaluation.warnings.length) {
    lines.push('## 警告');
    lines.push('');
    for (const warning of report.evaluation.warnings) lines.push(`- ${warning}`);
    lines.push('');
  }
  lines.push('## 关键参数');
  lines.push('');
  lines.push('| 参数 | 当前值 | 来源 | 待重启 |');
  lines.push('| --- | ---: | --- | --- |');
  for (const item of report.settings) {
    lines.push(`| ${item.name} | ${item.value} | ${item.source} | ${item.pendingRestart ? '是' : '否'} |`);
  }
  lines.push('');
  lines.push('## 连接与等待');
  lines.push('');
  lines.push('| state | wait_event_type | wait_event | count |');
  lines.push('| --- | --- | --- | ---: |');
  for (const item of report.activityByWait) {
    lines.push(`| ${item.state || '-'} | ${item.wait_event_type || '-'} | ${item.wait_event || '-'} | ${item.count} |`);
  }
  lines.push('');
  lines.push('## 缓存与事务');
  lines.push('');
  lines.push('| datname | commits | rollbacks | cache_hit_ratio |');
  lines.push('| --- | ---: | ---: | ---: |');
  for (const item of report.databaseStats) {
    lines.push(`| ${item.datname} | ${item.xact_commit} | ${item.xact_rollback} | ${item.cache_hit_ratio ?? '-'} |`);
  }
  lines.push('');
  lines.push('## 大表规模');
  lines.push('');
  lines.push('| 表 | 估算行数 | 总大小 | 索引大小 |');
  lines.push('| --- | ---: | ---: | ---: |');
  for (const item of report.largeRelations) {
    lines.push(`| ${item.relation} | ${item.estimated_rows} | ${item.total_size} | ${item.index_size} |`);
  }
  lines.push('');
  if (Array.isArray(report.pgStatStatements)) {
    lines.push('## pg_stat_statements Top SQL');
    lines.push('');
    lines.push('| calls | total_exec_ms | mean_exec_ms | rows | query |');
    lines.push('| ---: | ---: | ---: | ---: | --- |');
    for (const item of report.pgStatStatements) {
      lines.push(`| ${item.calls} | ${item.total_exec_ms} | ${item.mean_exec_ms} | ${item.rows} | ${String(item.query || '').replaceAll('|', '\\|')} |`);
    }
    lines.push('');
  } else {
    lines.push('## pg_stat_statements');
    lines.push('');
    lines.push(`未采集：${report.pgStatStatements?.message || 'extension/view unavailable'}`);
    lines.push('');
  }
  return `${lines.join('\n')}\n`;
}

function sqlQuote(value) {
  return String(value).replaceAll("'", "''");
}

function alterSystemSql(profile) {
  const lines = [
    `-- PostgreSQL tuning profile: ${profile.label}`,
    '-- Review current values and take a snapshot before applying this file.',
    '-- Run npm run perf:postgres:evidence -- --strict after reload/restart.',
    '',
  ];
  for (const [name, rule] of Object.entries(profile.settings)) {
    lines.push(`alter system set ${name} = '${sqlQuote(rule.recommended)}';`);
  }
  lines.push('select pg_reload_conf();');
  return `${lines.join('\n')}\n`;
}

async function main() {
  const options = parseArgs(process.argv);
  if (options.printSql) {
    console.log(alterSystemSql(options.profileDefinition));
    return;
  }
  const pool = new pg.Pool({ connectionString: databaseUrl, max: 2 });
  try {
    const settingsRaw = await query(
      pool,
      `
      select name, setting, unit, source, pending_restart
      from pg_settings
      where name = any($1::text[])
      order by array_position($1::text[], name)
      `,
      [options.settingNames],
    );
    const activityByWait = await query(
      pool,
      `
      select state, wait_event_type, wait_event, count(*)::int as count
      from pg_stat_activity
      where datname = current_database()
      group by state, wait_event_type, wait_event
      order by count desc, state nulls last
      `,
    );
    const databaseStats = await query(
      pool,
      `
      select datname,
             xact_commit::text,
             xact_rollback::text,
             blks_read::text,
             blks_hit::text,
             round(blks_hit * 100.0 / nullif(blks_hit + blks_read, 0), 2)::text as cache_hit_ratio
      from pg_stat_database
      where datname = current_database()
      `,
    );
    const bgwriter = await maybeQuery(
      pool,
      `
      select checkpoints_timed::text, checkpoints_req::text,
             checkpoint_write_time::text, checkpoint_sync_time::text
      from pg_stat_bgwriter
      `,
    );
    const largeRelations = await query(
      pool,
      `
      select relid::regclass::text as relation,
             n_live_tup::bigint::text as estimated_rows,
             pg_size_pretty(pg_total_relation_size(relid)) as total_size,
             pg_size_pretty(pg_indexes_size(relid)) as index_size
      from pg_stat_user_tables
      where schemaname = 'public'
      order by pg_total_relation_size(relid) desc
      limit 20
      `,
    );
    const pgStatStatements = await maybeQuery(
      pool,
      `
      select calls::bigint::text,
             round(total_exec_time::numeric, 2)::text as total_exec_ms,
             round(mean_exec_time::numeric, 2)::text as mean_exec_ms,
             rows::bigint::text,
             left(regexp_replace(query, '\\s+', ' ', 'g'), 180) as query
      from pg_stat_statements
      order by total_exec_time desc
      limit 10
      `,
    );
    const report = {
      generatedAt: new Date().toISOString(),
      databaseUrl: redactUrl(databaseUrl),
      profile: {
        name: options.profileDefinition.name,
        label: options.profileDefinition.label,
        description: options.profileDefinition.description,
      },
      evaluation: evaluate(settingsRaw, options.profileDefinition, options, pgStatStatements),
      settings: settingsRaw.map(explainSetting),
      activityByWait,
      databaseStats,
      bgwriter,
      largeRelations,
      pgStatStatements,
    };
    const pendingRestart = settingsRaw.filter(row => row.pending_restart).length;
    await fs.mkdir(outputDir, { recursive: true });
    const jsonPath = path.join(outputDir, `postgres-tuning-evidence-${shanghaiStamp()}.json`);
    const mdPath = jsonPath.replace(/\.json$/, '.md');
    await fs.writeFile(jsonPath, `${JSON.stringify(report, null, 2)}\n`, 'utf8');
    await fs.writeFile(mdPath, markdown(report), 'utf8');
    const payload = {
      status: report.evaluation.status,
      profile: report.profile.name,
      warnings: report.evaluation.warnings.length,
      failures: report.evaluation.failures.length,
      pgStatStatementsAvailable: !pgStatStatements?.unavailable,
      pendingRestart,
      jsonPath,
      mdPath,
    };
    if (options.json) {
      console.log(JSON.stringify(payload, null, 2));
    } else {
      console.log(`[pg-evidence] status=${report.evaluation.status}`);
      for (const failure of report.evaluation.failures) console.log(`[pg-evidence] failure: ${failure}`);
      for (const warning of report.evaluation.warnings) console.log(`[pg-evidence] warning: ${warning}`);
      console.log(`[pg-evidence] wrote ${jsonPath}`);
      console.log(`[pg-evidence] wrote ${mdPath}`);
    }
    if (options.strict && report.evaluation.failures.length > 0) process.exitCode = 1;
  } finally {
    await pool.end();
  }
}

main().catch(error => {
  console.error(error);
  process.exit(1);
});