import { mkdir, readFile, rename, rm, writeFile } from "node:fs/promises"
import { dirname } from "node:path"

export const DEFAULT_MODELS_URL = "https://api.commandcode.ai/provider/v1/models"
export const DEFAULT_MODELS_TIMEOUT_MS = 10_000

const DEFAULT_MAX_OUTPUT_TOKENS = 65_536
const MODEL_CACHE_VERSION = 1

export type PiThinkingLevel = "off" | "minimal" | "low" | "medium" | "high" | "xhigh" | "max"

type CommandCodeReasoningEffort = Exclude<PiThinkingLevel, "off">

/**
 * Per-model reasoning efforts supported by Command Code's generate endpoint.
 *
 * The Provider API does not expose reasoning metadata. This is an exact
 * snapshot of `reasoningEfforts` from the command-code@1.14.1 model catalog
 * (`packages/shared/src/model-catalog.ts`, also published in the generated
 * `dist/bundled/command-code-knowledge/reference/models.md`). Models omitted
 * here let Command Code choose their reasoning depth, matching the CLI.
 */
export const MODEL_EFFORTS: Readonly<Record<string, readonly CommandCodeReasoningEffort[]>> = {
  "Qwen/Qwen3.8-Max": ["low", "medium", "xhigh"],
  "claude-fable-5": ["low", "medium", "high", "xhigh", "max"],
  "claude-opus-4-7": ["low", "medium", "high", "xhigh", "max"],
  "claude-opus-4-8": ["low", "medium", "high", "xhigh", "max"],
  "claude-opus-5": ["low", "medium", "high", "xhigh", "max"],
  "claude-sonnet-4-6": ["low", "medium", "high", "xhigh", "max"],
  "claude-sonnet-5": ["low", "medium", "high", "xhigh", "max"],
  "deepseek/deepseek-v4-flash": ["high", "max"],
  "deepseek/deepseek-v4-pro": ["high", "max"],
  "gpt-5.3-codex": ["low", "medium", "high", "xhigh"],
  "gpt-5.4": ["low", "medium", "high", "xhigh"],
  "gpt-5.4-mini": ["low", "medium", "high"],
  "gpt-5.5": ["low", "medium", "high", "xhigh"],
  "gpt-5.6-luna": ["low", "medium", "high", "xhigh", "max"],
  "gpt-5.6-sol": ["low", "medium", "high", "xhigh", "max"],
  "gpt-5.6-terra": ["low", "medium", "high", "xhigh", "max"],
  "google/gemini-3.1-flash-lite": ["low", "medium", "high"],
  "google/gemini-3.5-flash": ["low", "medium", "high"],
  "google/gemini-3.5-flash-lite": ["low", "medium", "high"],
  "google/gemini-3.6-flash": ["low", "medium", "high"],
  "sakana/fugu-ultra": ["high", "xhigh"],
  "xai/grok-4.5": ["low", "medium", "high"],
  "zai-org/GLM-5.2": ["high", "max"],
}

const PI_THINKING_LEVELS: readonly PiThinkingLevel[] = [
  "off",
  "minimal",
  "low",
  "medium",
  "high",
  "xhigh",
  "max",
]

export function thinkingLevelMapForEfforts(
  efforts: readonly string[],
): Partial<Record<PiThinkingLevel, string | null>> {
  const map: Partial<Record<PiThinkingLevel, string | null>> = {}
  for (const level of PI_THINKING_LEVELS) {
    if (level === "off") continue
    map[level] = efforts.includes(level) ? level : null
  }
  return map
}

export interface ThinkingMetadata {
  thinkingLevelMap: Partial<Record<PiThinkingLevel, string | null>>
  thinking: {
    mode: "effort"
    effortMap: Partial<Record<CommandCodeReasoningEffort, string>>
    efforts: readonly CommandCodeReasoningEffort[]
  }
}

export function thinkingMetadataForModel(modelId: string): ThinkingMetadata | undefined {
  const efforts = MODEL_EFFORTS[modelId]
  if (!efforts) return undefined
  return {
    thinkingLevelMap: thinkingLevelMapForEfforts(efforts),
    thinking: {
      mode: "effort",
      effortMap: Object.fromEntries(efforts.map((effort) => [effort, effort])),
      efforts,
    },
  }
}

function isReasoningModel(modelId: string): boolean {
  return MODEL_EFFORTS[modelId] !== undefined
}

interface ApiModel {
  id: string
  name: string
  contextLength: number
}

export interface CommandCodeModel {
  id: string
  name: string
  reasoning: boolean
  contextWindow: number
  maxTokens: number
}

interface FetchCommandCodeModelsOptions {
  url?: string
  fetchImpl?: typeof fetch
  signal?: AbortSignal
  timeoutMs?: number
}

interface LoadCommandCodeModelsOptions extends FetchCommandCodeModelsOptions {
  cachePath: string
}

export interface LoadCommandCodeModelsResult {
  models: readonly CommandCodeModel[]
  source: "live" | "cache" | "empty"
  warning?: string
}

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === "object" && value !== null && !Array.isArray(value)
}

function stringField(record: Record<string, unknown>, key: string): string {
  const value = record[key]
  if (typeof value !== "string" || value.length === 0) {
    throw new Error(`Expected ${key} to be a non-empty string`)
  }
  return value
}

function booleanField(record: Record<string, unknown>, key: string): boolean {
  const value = record[key]
  if (typeof value !== "boolean") throw new Error(`Expected ${key} to be a boolean`)
  return value
}

function positiveNumberField(record: Record<string, unknown>, key: string): number {
  const value = record[key]
  if (typeof value !== "number" || !Number.isFinite(value) || value <= 0) {
    throw new Error(`Expected ${key} to be a positive number`)
  }
  return value
}

function parseApiModel(value: unknown): ApiModel {
  if (!isRecord(value)) throw new Error("Expected model entry to be an object")

  return {
    id: stringField(value, "id"),
    name: stringField(value, "name"),
    contextLength: positiveNumberField(value, "context_length"),
  }
}

function parseCachedModel(value: unknown): CommandCodeModel {
  if (!isRecord(value)) throw new Error("Expected cached model entry to be an object")

  const id = stringField(value, "id")
  booleanField(value, "reasoning")
  return {
    id,
    name: stringField(value, "name"),
    reasoning: isReasoningModel(id),
    contextWindow: positiveNumberField(value, "contextWindow"),
    maxTokens: positiveNumberField(value, "maxTokens"),
  }
}

function requireModels(models: readonly CommandCodeModel[]): readonly CommandCodeModel[] {
  if (models.length === 0) throw new Error("Command Code returned an empty model catalog")
  return models
}

function errorMessage(error: unknown): string {
  return error instanceof Error ? error.message : String(error)
}

function abortError(reason: unknown): Error {
  if (reason instanceof Error) return reason
  return new DOMException("The operation was aborted", "AbortError")
}

function configuredTimeoutMs(timeoutMs: number | undefined): number {
  return timeoutMs !== undefined && Number.isFinite(timeoutMs) && timeoutMs > 0
    ? timeoutMs
    : DEFAULT_MODELS_TIMEOUT_MS
}

export function getModelsTimeoutMs(env: NodeJS.ProcessEnv = process.env): number {
  const raw = env.COMMANDCODE_MODELS_TIMEOUT_MS
  if (!raw) return DEFAULT_MODELS_TIMEOUT_MS

  const parsed = Number(raw)
  return configuredTimeoutMs(parsed)
}

class ModelDiscoveryTimeoutError extends Error {
  constructor(timeoutMs: number) {
    super(`Command Code model discovery timed out after ${timeoutMs}ms`)
    this.name = "ModelDiscoveryTimeoutError"
  }
}

function runWithTimeout<T>(
  operation: (signal: AbortSignal) => Promise<T>,
  timeoutMs: number,
  externalSignal: AbortSignal | undefined,
): Promise<T> {
  const controller = new AbortController()
  let timer: ReturnType<typeof setTimeout> | undefined
  let settled = false
  let onExternalAbort: (() => void) | undefined

  return new Promise<T>((resolve, reject) => {
    const cleanup = () => {
      if (timer !== undefined) clearTimeout(timer)
      if (onExternalAbort && externalSignal) {
        externalSignal.removeEventListener("abort", onExternalAbort)
      }
    }

    const resolveOnce = (value: T) => {
      if (settled) return
      settled = true
      cleanup()
      resolve(value)
    }

    const rejectOnce = (error: unknown) => {
      if (settled) return
      settled = true
      cleanup()
      reject(error)
    }

    const abort = (reason: unknown) => {
      const error = abortError(reason)
      controller.abort(error)
      rejectOnce(error)
    }

    if (externalSignal?.aborted) {
      abort(externalSignal.reason)
      return
    }

    onExternalAbort = () => abort(externalSignal?.reason)
    externalSignal?.addEventListener("abort", onExternalAbort, { once: true })
    timer = setTimeout(() => abort(new ModelDiscoveryTimeoutError(timeoutMs)), timeoutMs)

    Promise.resolve()
      .then(() => operation(controller.signal))
      .then(resolveOnce, rejectOnce)
  })
}

export function commandCodeModelsFromApiResponse(value: unknown): readonly CommandCodeModel[] {
  if (!isRecord(value)) throw new Error("Expected models response to be an object")
  if (value.object !== "list") throw new Error("Expected models response object to be 'list'")

  const data = value.data
  if (!Array.isArray(data)) throw new Error("Expected models response data to be an array")

  return data.map(parseApiModel).map((model) => ({
    id: model.id,
    name: `${model.name} (CC)`,
    reasoning: isReasoningModel(model.id),
    contextWindow: model.contextLength,
    maxTokens: Math.min(model.contextLength, DEFAULT_MAX_OUTPUT_TOKENS),
  }))
}

export function commandCodeModelsFromCache(value: unknown): readonly CommandCodeModel[] {
  if (!isRecord(value)) throw new Error("Expected model cache to be an object")
  if (value.version !== MODEL_CACHE_VERSION) {
    throw new Error(`Expected model cache version ${MODEL_CACHE_VERSION}`)
  }
  if (!Array.isArray(value.models)) throw new Error("Expected cached models to be an array")

  return requireModels(value.models.map(parseCachedModel))
}

export async function fetchCommandCodeModels(
  options: FetchCommandCodeModelsOptions = {},
): Promise<readonly CommandCodeModel[]> {
  const url = options.url ?? DEFAULT_MODELS_URL
  const fetchImpl = options.fetchImpl ?? fetch
  const body: unknown = await runWithTimeout(
    async (signal) => {
      const response = await fetchImpl(url, {
        headers: {
          accept: "application/json",
        },
        signal,
      })

      if (!response.ok) {
        throw new Error(
          `Failed to fetch Command Code models: ${response.status} ${response.statusText}`,
        )
      }

      return await response.json()
    },
    configuredTimeoutMs(options.timeoutMs),
    options.signal,
  )
  return requireModels(commandCodeModelsFromApiResponse(body))
}

async function readCommandCodeModelsCache(cachePath: string): Promise<readonly CommandCodeModel[]> {
  const contents = await readFile(cachePath, "utf-8")
  const parsed: unknown = JSON.parse(contents)
  return commandCodeModelsFromCache(parsed)
}

async function writeCommandCodeModelsCache(
  cachePath: string,
  models: readonly CommandCodeModel[],
): Promise<void> {
  await mkdir(dirname(cachePath), { recursive: true })
  const temporaryPath = `${cachePath}.${process.pid}.tmp`

  try {
    await writeFile(
      temporaryPath,
      `${JSON.stringify({ version: MODEL_CACHE_VERSION, models }, null, 2)}\n`,
      { encoding: "utf-8", mode: 0o600 },
    )
    await rename(temporaryPath, cachePath)
  } finally {
    try {
      await rm(temporaryPath, { force: true })
    } catch {
      // Best-effort cleanup must not hide the original cache write error.
    }
  }
}

export async function loadCommandCodeModels(
  options: LoadCommandCodeModelsOptions,
): Promise<LoadCommandCodeModelsResult> {
  const cachePath = options.cachePath

  try {
    const models = await fetchCommandCodeModels(options)

    try {
      await writeCommandCodeModelsCache(cachePath, models)
      return { models, source: "live" }
    } catch (error) {
      return {
        models,
        source: "live",
        warning: `Loaded the live Command Code model catalog but could not update ${cachePath}: ${errorMessage(error)}`,
      }
    }
  } catch (liveError) {
    if (options.signal?.aborted) throw abortError(options.signal.reason ?? liveError)

    try {
      const models = await readCommandCodeModelsCache(cachePath)
      return {
        models,
        source: "cache",
        warning: `Could not refresh the Command Code model catalog (${errorMessage(liveError)}). Using the cached catalog from ${cachePath}.`,
      }
    } catch (cacheError) {
      return {
        models: [],
        source: "empty",
        warning: `Could not refresh the Command Code model catalog (${errorMessage(liveError)}), and no valid cached catalog is available at ${cachePath} (${errorMessage(cacheError)}). Command Code models will remain unavailable until /commandcode-refresh succeeds.`,
      }
    }
  }
}