export const postgresTuningProfiles = {
  'shared-host': {
    name: 'shared-host',
    label: '4c16g shared-host',
    description: '4 vCPU / 16GB RAM, PostgreSQL shares the host with API, worker, Nginx and monitoring agents.',
    settings: {
      max_connections: {
        recommended: '80',
        min: 40,
        max: 120,
        type: 'number',
        rationale: '4 vCPU should use application/pooler limits instead of many direct active connections.',
      },
      shared_buffers: {
        recommended: '3GB',
        min: '2GB',
        max: '4GB',
        type: 'bytes',
        restart: true,
        rationale: 'Keep PostgreSQL buffers large enough while leaving RAM for OS cache and sibling services.',
      },
      effective_cache_size: {
        recommended: '10GB',
        min: '8GB',
        max: '12GB',
        type: 'bytes',
        rationale: 'Planner estimate only; reflects shared buffers plus OS cache on a 16GB shared host.',
      },
      work_mem: {
        recommended: '16MB',
        min: '8MB',
        max: '32MB',
        type: 'bytes',
        rationale: 'This is per sort/hash operation, not a global cap.',
      },
      maintenance_work_mem: {
        recommended: '512MB',
        min: '256MB',
        max: '1GB',
        type: 'bytes',
        rationale: 'Helps index builds, vacuum and imports without overcommitting memory.',
      },
      autovacuum_work_mem: {
        recommended: '256MB',
        min: '128MB',
        max: '512MB',
        type: 'bytes',
        rationale: 'Avoid letting multiple autovacuum workers inherit an overly high maintenance_work_mem.',
      },
      wal_buffers: {
        recommended: '16MB',
        min: '8MB',
        max: '64MB',
        type: 'bytes',
        restart: true,
        rationale: 'Enough WAL buffering for steady learning writes and import bursts.',
      },
      min_wal_size: {
        recommended: '1GB',
        min: '1GB',
        max: '4GB',
        type: 'bytes',
        rationale: 'Reserve WAL for short write spikes and batch jobs.',
      },
      max_wal_size: {
        recommended: '6GB',
        min: '4GB',
        max: '12GB',
        type: 'bytes',
        rationale: 'Reduce checkpoint pressure while keeping crash recovery bounded.',
      },
      checkpoint_timeout: {
        recommended: '10min',
        min: '5min',
        max: '15min',
        type: 'duration',
        rationale: 'Avoid overly frequent checkpoints on write bursts.',
      },
      checkpoint_completion_target: {
        recommended: '0.9',
        min: 0.8,
        max: 0.95,
        type: 'number',
        rationale: 'Spread checkpoint I/O without pushing completion too close to the next checkpoint.',
      },
      effective_io_concurrency: {
        recommended: '100',
        min: 50,
        max: 300,
        type: 'number',
        rationale: 'SSD cloud disk starting point; validate against the actual disk class.',
      },
      random_page_cost: {
        recommended: '1.1',
        min: 1,
        max: 1.5,
        type: 'number',
        rationale: 'Reflect SSD random I/O and encourage reasonable index scans.',
      },
      jit: {
        recommended: 'off',
        exact: 'off',
        type: 'text',
        rationale: 'Question-bank API queries are mostly short OLTP requests where JIT planning cost is usually not worth it.',
      },
      log_min_duration_statement: {
        recommended: '500ms',
        min: '100ms',
        max: '1000ms',
        type: 'duration',
        rationale: 'Capture slow SQL during launch without logging every normal request.',
      },
      idle_in_transaction_session_timeout: {
        recommended: '60s',
        min: '30s',
        max: '120s',
        type: 'duration',
        rationale: 'Kill idle transactions before they block migrations and writes.',
      },
      statement_timeout: {
        recommended: '30s',
        min: '5s',
        max: '60s',
        type: 'duration',
        rationale: 'API requests should fail boundedly; import jobs can override per session.',
      },
      lock_timeout: {
        recommended: '5s',
        min: '1s',
        max: '10s',
        type: 'duration',
        rationale: 'Ordinary API requests should not wait a long time behind locks.',
      },
    },
  },
  'dedicated-db': {
    name: 'dedicated-db',
    label: '4c16g dedicated PostgreSQL',
    description: '4 vCPU / 16GB RAM where PostgreSQL is the only heavy service on the host.',
    settings: {
      max_connections: { recommended: '120', min: 60, max: 150, type: 'number' },
      shared_buffers: { recommended: '4GB', min: '3GB', max: '5GB', type: 'bytes', restart: true },
      effective_cache_size: { recommended: '12GB', min: '10GB', max: '14GB', type: 'bytes' },
      work_mem: { recommended: '16MB', min: '8MB', max: '32MB', type: 'bytes' },
      maintenance_work_mem: { recommended: '768MB', min: '512MB', max: '1536MB', type: 'bytes' },
      autovacuum_work_mem: { recommended: '256MB', min: '128MB', max: '512MB', type: 'bytes' },
      wal_buffers: { recommended: '16MB', min: '8MB', max: '64MB', type: 'bytes', restart: true },
      min_wal_size: { recommended: '2GB', min: '1GB', max: '4GB', type: 'bytes' },
      max_wal_size: { recommended: '8GB', min: '4GB', max: '16GB', type: 'bytes' },
      checkpoint_timeout: { recommended: '15min', min: '5min', max: '20min', type: 'duration' },
      checkpoint_completion_target: { recommended: '0.9', min: 0.8, max: 0.95, type: 'number' },
      effective_io_concurrency: { recommended: '100', min: 50, max: 300, type: 'number' },
      random_page_cost: { recommended: '1.1', min: 1, max: 1.5, type: 'number' },
      jit: { recommended: 'off', exact: 'off', type: 'text' },
      log_min_duration_statement: { recommended: '500ms', min: '100ms', max: '1000ms', type: 'duration' },
      idle_in_transaction_session_timeout: { recommended: '60s', min: '30s', max: '120s', type: 'duration' },
      statement_timeout: { recommended: '30s', min: '5s', max: '60s', type: 'duration' },
      lock_timeout: { recommended: '5s', min: '1s', max: '10s', type: 'duration' },
    },
  },
};

export const defaultPostgresTuningProfile = 'shared-host';

export function getPostgresTuningProfile(name = defaultPostgresTuningProfile) {
  const profile = postgresTuningProfiles[name];
  if (!profile) {
    throw new Error(`Unknown PostgreSQL tuning profile: ${name}`);
  }
  return profile;
}

export function getPostgresTuningSettingNames(profileName = defaultPostgresTuningProfile) {
  return Object.keys(getPostgresTuningProfile(profileName).settings);
}