import fs from 'node:fs/promises'
import path from 'node:path'
import process from 'node:process'
import { pathToFileURL } from 'node:url'

export const CONFIG_FILE_NAMES = [
  'yx-generate-api.config.mjs',
  'yx-generate-api.config.js',
  'yx-generate-api.config.cjs',
]

export const PARAM_STYLE = {
  OBJECT: 'object',
  POSITIONAL: 'positional',
}

export const SUPPORTED_PARAM_STYLES = Object.values(PARAM_STYLE)
export const DEFAULT_SWAGGER_TIMEOUT_MS = 20_000

export const DEFAULT_SYNC_OPTIONS = {
  blockStart: '// AUTO-GENERATED API EXPORTS START',
  blockEnd: '// AUTO-GENERATED API EXPORTS END',
  includeGeneratedIndexSnapshot: true,
  snapshotTitle: '// generated/index.js content:',
}

export const loadProjectConfig = async ({ configPath, cwd = process.cwd() } = {}) => {
  const resolvedConfigPath = await resolveConfigPath({ configPath, cwd })
  const importedConfig = await import(
    `${pathToFileURL(resolvedConfigPath).href}?cacheBust=${Date.now()}`
  )
  const rawConfig = importedConfig.default ?? importedConfig

  if (!rawConfig || typeof rawConfig !== 'object') {
    throw new Error(`Config file must export an object: ${resolvedConfigPath}`)
  }

  const rootDir = path.dirname(resolvedConfigPath)
  const syncConfig = rawConfig.sync || {}
  const externalIndexFile = rawConfig.externalIndexFile
    ? resolveProjectPath(rootDir, rawConfig.externalIndexFile)
    : null

  return {
    configPath: resolvedConfigPath,
    rootDir,
    swaggerUrl: rawConfig.swaggerUrl ? resolveSwaggerSource(rootDir, rawConfig.swaggerUrl) : '',
    swaggerTimeoutMs: normalizePositiveInteger(
      rawConfig.swaggerTimeoutMs,
      'swaggerTimeoutMs',
      DEFAULT_SWAGGER_TIMEOUT_MS,
    ),
    outputDir: rawConfig.outputDir
      ? resolveProjectPath(rootDir, rawConfig.outputDir)
      : resolveProjectPath(rootDir, 'src/api/generated'),
    generateIndexFile: rawConfig.generateIndexFile ?? true,
    externalIndexFile,
    requestImport: normalizeString(rawConfig.requestImport) || '../request',
    paramStyle: normalizeParamStyle(rawConfig.paramStyle || PARAM_STYLE.OBJECT),
    cleanOutput: rawConfig.cleanOutput ?? true,
    sync: {
      enabled: syncConfig.enabled ?? Boolean(externalIndexFile && (rawConfig.generateIndexFile ?? true)),
      blockStart: normalizeString(syncConfig.blockStart) || DEFAULT_SYNC_OPTIONS.blockStart,
      blockEnd: normalizeString(syncConfig.blockEnd) || DEFAULT_SYNC_OPTIONS.blockEnd,
      includeGeneratedIndexSnapshot:
        syncConfig.includeGeneratedIndexSnapshot ??
        DEFAULT_SYNC_OPTIONS.includeGeneratedIndexSnapshot,
      snapshotTitle:
        normalizeString(syncConfig.snapshotTitle) || DEFAULT_SYNC_OPTIONS.snapshotTitle,
      exportFrom: normalizeString(syncConfig.exportFrom) || null,
    },
  }
}

export const resolveConfigPath = async ({ configPath, cwd = process.cwd() } = {}) => {
  if (configPath) {
    const explicitPath = path.resolve(cwd, configPath)
    await assertFileExists(explicitPath, `Config file not found: ${explicitPath}`)
    return explicitPath
  }

  for (const fileName of CONFIG_FILE_NAMES) {
    const candidatePath = path.resolve(cwd, fileName)

    if (await fileExists(candidatePath)) {
      return candidatePath
    }
  }

  throw new Error(
    `Config file not found in ${cwd}. Expected one of: ${CONFIG_FILE_NAMES.join(', ')}`,
  )
}

export const resolveCwdPath = (cwd, targetPath) => {
  return path.resolve(cwd, targetPath)
}

export const resolveProjectPath = (projectRoot, targetPath) => {
  return path.isAbsolute(targetPath) ? targetPath : path.resolve(projectRoot, targetPath)
}

export const resolveSwaggerSource = (baseDir, source) => {
  const normalizedSource = normalizeString(source)

  if (!normalizedSource) {
    return ''
  }

  if (/^https?:\/\//i.test(normalizedSource) || /^file:\/\//i.test(normalizedSource)) {
    return normalizedSource
  }

  return resolveProjectPath(baseDir, normalizedSource)
}

export const normalizeParamStyle = (value) => {
  const normalizedValue = normalizeString(value).toLowerCase()

  if (SUPPORTED_PARAM_STYLES.includes(normalizedValue)) {
    return normalizedValue
  }

  throw new Error(
    `Unsupported paramStyle: ${value}. Expected one of: ${SUPPORTED_PARAM_STYLES.join(' / ')}`,
  )
}

const normalizeString = (value) => {
  return String(value || '').trim()
}

const normalizePositiveInteger = (value, label, fallbackValue) => {
  if (value === undefined || value === null || String(value).trim() === '') {
    return fallbackValue
  }

  const parsedValue = Number.parseInt(String(value), 10)

  if (!Number.isInteger(parsedValue) || parsedValue <= 0) {
    throw new Error(`${label} must be a positive integer. Received: ${value}`)
  }

  return parsedValue
}

const fileExists = async (targetPath) => {
  try {
    await fs.access(targetPath)
    return true
  } catch {
    return false
  }
}

const assertFileExists = async (targetPath, errorMessage) => {
  if (!(await fileExists(targetPath))) {
    throw new Error(errorMessage)
  }
}