import type {
  PlaybookAutonomy,
  PlaybookCatalogQuery,
  PlaybookLifecycle,
  PlaybookMode,
  PlaybookQualityStatus,
  PlaybookRiskTier,
  PlaybookSort,
  PlaybookSource,
  PlaybookType,
} from '@devrunbook/db'

export class PlaybookQueryError extends Error {}

const allowedParameters = new Set([
  'q',
  'category',
  'type',
  'mode',
  'autonomy',
  'riskTier',
  'stack',
  'lifecycle',
  'quality',
  'source',
  'favorite',
  'sort',
  'cursor',
  'limit',
])
const playbookTypes = new Set<PlaybookType>(['quick', 'guided', 'run-pack'])
const modes = new Set<PlaybookMode>([
  'inspect',
  'plan',
  'guided',
  'execute',
  'recovery',
])
const autonomies = new Set<PlaybookAutonomy>([
  'observe',
  'diagnose',
  'plan',
  'implement',
  'verify',
  'repair',
])
const riskTiers = new Set<PlaybookRiskTier>([
  'low',
  'moderate',
  'high',
  'critical',
])
const lifecycles = new Set<PlaybookLifecycle>([
  'draft',
  'reviewed',
  'validated',
  'battle-tested',
  'deprecated',
])
const sources = new Set<PlaybookSource>(['built_in', 'private', 'imported'])
const qualities = new Set<PlaybookQualityStatus>([
  'unreviewed',
  'editorial-reviewed',
  'technical-reviewed',
  'evaluation-backed',
])
const sorts = new Set<PlaybookSort>([
  'relevance',
  'updated',
  'title',
  'quality',
])

export interface ParsedPlaybookQuery {
  readonly catalog: PlaybookCatalogQuery
  readonly cursor?: string
  readonly limit: number
}

export function encodePlaybookCursor(offset: number): string {
  return Buffer.from(`offset:${offset}`, 'utf8').toString('base64url')
}

export function decodePlaybookCursor(cursor: string | undefined): number {
  if (!cursor) return 0
  const match = /^offset:(\d+)$/u.exec(
    Buffer.from(cursor, 'base64url').toString('utf8'),
  )
  const offset = match ? Number(match[1]) : Number.NaN
  if (!Number.isSafeInteger(offset) || offset < 0) {
    throw new PlaybookQueryError('cursor is malformed')
  }
  return offset
}

function values(parameters: URLSearchParams, name: string): string[] {
  return parameters
    .getAll(name)
    .flatMap((value) => value.split(','))
    .map((value) => value.trim())
    .filter(Boolean)
}

function enums<T extends string>(
  parameters: URLSearchParams,
  name: string,
  allowed: ReadonlySet<T>,
): T[] | undefined {
  const parsed = values(parameters, name)
  if (parsed.some((value) => !allowed.has(value as T))) {
    throw new PlaybookQueryError(`${name} contains an unsupported value`)
  }
  return parsed.length > 0 ? (parsed as T[]) : undefined
}

export function parsePlaybookQuery(url: string): ParsedPlaybookQuery {
  const parameters = new URL(url).searchParams
  for (const name of parameters.keys()) {
    if (!allowedParameters.has(name)) {
      throw new PlaybookQueryError(`Unsupported query parameter: ${name}`)
    }
  }
  const q = parameters.get('q')?.trim()
  if (q && q.length > 200)
    throw new PlaybookQueryError('q must be at most 200 characters')
  const category = values(parameters, 'category')
  const stack = values(parameters, 'stack')
  if ([...category, ...stack].some((value) => value.length > 80)) {
    throw new PlaybookQueryError(
      'category and stack values must be at most 80 characters',
    )
  }
  const type = enums(parameters, 'type', playbookTypes)
  const mode = enums(parameters, 'mode', modes)
  const autonomy = enums(parameters, 'autonomy', autonomies)
  const riskTier = enums(parameters, 'riskTier', riskTiers)
  const lifecycle = enums(parameters, 'lifecycle', lifecycles)
  const quality = enums(parameters, 'quality', qualities)
  const source = enums(parameters, 'source', sources)
  const sortValues = values(parameters, 'sort')
  if (
    sortValues.length > 1 ||
    (sortValues[0] && !sorts.has(sortValues[0] as PlaybookSort))
  ) {
    throw new PlaybookQueryError('sort contains an unsupported value')
  }
  const favoriteValues = values(parameters, 'favorite')
  if (
    favoriteValues.length > 1 ||
    (favoriteValues[0] && !['true', 'false'].includes(favoriteValues[0]))
  ) {
    throw new PlaybookQueryError('favorite must be true or false')
  }
  const cursor = parameters.get('cursor')?.trim()
  if (cursor && !/^[A-Za-z0-9_-]{1,500}$/u.test(cursor)) {
    throw new PlaybookQueryError('cursor is malformed')
  }
  if (cursor) decodePlaybookCursor(cursor)
  const rawLimit = parameters.get('limit')
  const limit = rawLimit === null ? 50 : Number(rawLimit)
  if (!Number.isInteger(limit) || limit < 1 || limit > 100) {
    throw new PlaybookQueryError('limit must be an integer from 1 to 100')
  }
  const catalog: PlaybookCatalogQuery = {
    ...(q ? { q } : {}),
    ...(category.length > 0 ? { category } : {}),
    ...(type ? { type } : {}),
    ...(mode ? { mode } : {}),
    ...(autonomy ? { autonomy } : {}),
    ...(riskTier ? { riskTier } : {}),
    ...(stack.length > 0 ? { stack } : {}),
    ...(lifecycle ? { lifecycle } : {}),
    ...(quality ? { quality } : {}),
    ...(source ? { source } : {}),
    ...(favoriteValues[0] === 'true' ? { favorite: true } : {}),
    ...(sortValues[0] ? { sort: sortValues[0] as PlaybookSort } : {}),
  }
  return { catalog, ...(cursor ? { cursor } : {}), limit }
}