import { validateSttBaseUrl } from './piagentui-server-core.js'
import type { StoredSttSettings, StoredTtsSettings } from './piagentui-settings-store.js'

export type SettingsUpdateResult<T> = { ok: true; next: T } | { ok: false; error: string }

type Fields = Record<string, unknown>
/** Assigns a validated value to `next`; returns false when the value is invalid. */
type FieldRule = (value: unknown, next: Fields) => boolean

const TTS_RESPONSE_FORMATS = ['mp3', 'opus', 'aac', 'flac', 'wav', 'pcm'] as const

export function isTtsResponseFormat(value: unknown): value is NonNullable<StoredTtsSettings['responseFormat']> {
  return typeof value === 'string' && (TTS_RESPONSE_FORMATS as readonly string[]).includes(value)
}

const booleanField =
  (key: string): FieldRule =>
  (value, next) => {
    next[key] = value === true
    return true
  }

const oneOfField =
  (key: string, allowed: readonly string[]): FieldRule =>
  (value, next) => {
    if (typeof value !== 'string' || !allowed.includes(value)) return false
    next[key] = value
    return true
  }

const endpointField =
  (key: string): FieldRule =>
  (value, next) => {
    if (typeof value !== 'string' || !value.startsWith('/')) return false
    next[key] = value
    return true
  }

const trimmedField =
  (key: string): FieldRule =>
  (value, next) => {
    if (typeof value !== 'string' || !value.trim()) return false
    next[key] = value.trim()
    return true
  }

const baseUrlField: FieldRule = (value, next) => {
  if (typeof value !== 'string' || !validateSttBaseUrl(value)) return false
  next.baseUrl = value.replace(/\/+$/, '')
  return true
}

const languageField: FieldRule = (value, next) => {
  if (value === null || value === '') delete next.language
  else if (typeof value === 'string') next.language = value.trim()
  else return false
  return true
}

const speedField: FieldRule = (value, next) => {
  if (typeof value !== 'number' || value < 0.25 || value > 4) return false
  next.speed = value
  return true
}

const PROVIDER_KINDS = ['openai', 'openai-compatible'] as const

const STT_RULES: Array<[string, FieldRule]> = [
  ['enabled', booleanField('enabled')],
  ['providerKind', oneOfField('providerKind', PROVIDER_KINDS)],
  ['mode', oneOfField('mode', ['file', 'realtime'])],
  ['baseUrl', baseUrlField],
  ['apiKeyRequired', booleanField('apiKeyRequired')],
  ['transcriptionEndpoint', endpointField('transcriptionEndpoint')],
  ['transcriptionModel', trimmedField('transcriptionModel')],
  ['language', languageField],
  ['insertMode', oneOfField('insertMode', ['append', 'replace'])],
]

const TTS_RULES: Array<[string, FieldRule]> = [
  ['enabled', booleanField('enabled')],
  ['providerKind', oneOfField('providerKind', PROVIDER_KINDS)],
  ['baseUrl', baseUrlField],
  ['apiKeyRequired', booleanField('apiKeyRequired')],
  ['speechEndpoint', endpointField('speechEndpoint')],
  ['model', trimmedField('model')],
  ['voice', trimmedField('voice')],
  ['responseFormat', oneOfField('responseFormat', TTS_RESPONSE_FORMATS)],
  ['speed', speedField],
]

function applyUpdate<T extends object>(
  existing: T,
  update: Record<string, unknown>,
  rules: Array<[string, FieldRule]>,
): SettingsUpdateResult<T> {
  const next: Fields = { ...(existing as Fields) }

  for (const [field, rule] of rules) {
    if (update[field] === undefined) continue
    if (!rule(update[field], next)) return { ok: false, error: `Invalid ${field}` }
  }

  if (Object.prototype.hasOwnProperty.call(update, 'apiKey')) {
    if (update.apiKey === null) delete next.apiKey
    else if (typeof update.apiKey === 'string' && update.apiKey.trim()) next.apiKey = update.apiKey.trim()
  }

  return { ok: true, next: next as T }
}

/** Validates a PATCH-style STT update against the stored settings. Pure: does not persist anything. */
export function applySttSettingsUpdate(
  existing: StoredSttSettings,
  update: Record<string, unknown>,
): SettingsUpdateResult<StoredSttSettings> {
  return applyUpdate(existing, update, STT_RULES)
}

/** Validates a PATCH-style TTS update against the stored settings. Pure: does not persist anything. */
export function applyTtsSettingsUpdate(
  existing: StoredTtsSettings,
  update: Record<string, unknown>,
): SettingsUpdateResult<StoredTtsSettings> {
  return applyUpdate(existing, update, TTS_RULES)
}