/**
 * Docker Engine version/capability cache and create-option validation.
 */
import { docker } from '../services/docker.js'
import logger from './logger.js'

/** @type {{ apiVersion: string, major: number, minor: number, os: string, experimental: boolean, fetchedAt: number }|null} */
let cached = null
const CACHE_MS = 60_000

/**
 * @returns {Promise<{ apiVersion: string, major: number, minor: number, os: string, experimental: boolean }>}
 */
export async function getEngineCapabilities() {
  const now = Date.now()
  if (cached && now - cached.fetchedAt < CACHE_MS) {
    return cached
  }
  const version = await docker.version()
  const apiVersion = String(version.ApiVersion || version.apiVersion || '1.40')
  const [maj, min] = apiVersion.split('.').map((n) => Number(n) || 0)
  cached = {
    apiVersion,
    major: maj,
    minor: min,
    os: version.Os || version.os || 'linux',
    experimental: Boolean(version.Experimental || version.experimental),
    fetchedAt: now,
  }
  return cached
}

/**
 * Compare semver-ish API versions: returns true if a.b >= major.minor
 * @param {{ major: number, minor: number }} cap
 * @param {number} major
 * @param {number} minor
 */
export function apiAtLeast(cap, major, minor) {
  if (cap.major > major) return true
  if (cap.major < major) return false
  return cap.minor >= minor
}

/**
 * Features that require minimum Engine API versions (approx Docker docs).
 * Keys are HostConfig / Config field names (case-insensitive match).
 */
const FIELD_MIN_API = {
  // HostConfig
  Init: [1, 25],
  Runtime: [1, 25],
  NanoCpus: [1, 25],
  CpuCount: [1, 25],
  CpuPercent: [1, 25],
  IOMaximumIOps: [1, 25],
  IOMaximumBandwidth: [1, 25],
  DeviceCgroupRules: [1, 28],
  DeviceRequests: [1, 40],
  Sysctls: [1, 24],
  PidsLimit: [1, 25],
  Isolation: [1, 24],
  MaskedPaths: [1, 25],
  ReadonlyPaths: [1, 25],
  Mounts: [1, 30],
  ConsoleSize: [1, 25],
  Annotations: [1, 43],
  // Config
  StopTimeout: [1, 25],
  Shell: [1, 25],
  Healthcheck: [1, 24],
  // Networking
  EndpointSettings: [1, 22],
  // Windows / platform
  Platform: [1, 32],
}

/**
 * Validate create/update options against the connected Engine API version.
 * @param {object} opts - docker createContainer body (may include HostConfig, name, start)
 * @param {{ strict?: boolean }} [options] - strict throws; soft returns warnings
 * @returns {Promise<{ ok: boolean, warnings: string[], errors: string[], apiVersion: string }>}
 */
export async function validateCreateOptions(opts, options = {}) {
  const strict = options.strict !== false
  const warnings = []
  const errors = []
  let cap
  try {
    cap = await getEngineCapabilities()
  } catch (err) {
    logger.warn('engine capabilities unavailable', { error: err.message })
    return { ok: true, warnings: ['Could not read Engine version; skipped capability check'], errors: [], apiVersion: 'unknown' }
  }

  const fields = collectFieldNames(opts)
  for (const field of fields) {
    const min = FIELD_MIN_API[field]
    if (!min) continue
    if (!apiAtLeast(cap, min[0], min[1])) {
      const msg = `Field "${field}" requires Docker API ≥ ${min[0]}.${min[1]} (engine reports ${cap.apiVersion})`
      if (strict) errors.push(msg)
      else warnings.push(msg)
    }
  }

  // Platform-specific checks
  if (opts.HostConfig?.Isolation && cap.os !== 'windows') {
    warnings.push('HostConfig.Isolation is primarily for Windows containers')
  }

  // Basic structural validation always hard-fails
  if (opts.Image != null && typeof opts.Image !== 'string') {
    errors.push('Image must be a string')
  }
  if (opts.Env != null && !Array.isArray(opts.Env)) {
    errors.push('Env must be an array of KEY=value strings')
  }
  if (opts.HostConfig?.PortBindings && typeof opts.HostConfig.PortBindings !== 'object') {
    errors.push('HostConfig.PortBindings must be an object')
  }
  if (opts.HostConfig?.Memory != null && Number(opts.HostConfig.Memory) < 0) {
    errors.push('HostConfig.Memory must be >= 0')
  }
  if (opts.HostConfig?.NanoCpus != null && Number(opts.HostConfig.NanoCpus) < 0) {
    errors.push('HostConfig.NanoCpus must be >= 0')
  }

  const ok = errors.length === 0
  return { ok, warnings, errors, apiVersion: cap.apiVersion }
}

/**
 * @param {object} opts
 * @returns {Set<string>}
 */
function collectFieldNames(opts) {
  const names = new Set()
  if (!opts || typeof opts !== 'object') return names
  for (const k of Object.keys(opts)) {
    if (k === 'name' || k === 'start' || k === 'update') continue
    names.add(k)
  }
  if (opts.HostConfig && typeof opts.HostConfig === 'object') {
    for (const k of Object.keys(opts.HostConfig)) names.add(k)
  }
  if (opts.Config && typeof opts.Config === 'object') {
    for (const k of Object.keys(opts.Config)) names.add(k)
  }
  if (opts.NetworkingConfig && typeof opts.NetworkingConfig === 'object') {
    names.add('EndpointSettings')
  }
  if (opts.Platform) names.add('Platform')
  if (opts.Healthcheck) names.add('Healthcheck')
  return names
}

export function clearEngineCapabilitiesCache() {
  cached = null
}