/**
 * YAML config loader with env-var overrides and validation.
 * @see .omo/plans/zcode-proxy.md Task 2
 */
import { readFileSync, existsSync } from "node:fs";
import { parse } from "yaml";
import type { ClientIdentityConfig, ProxyConfig, ProviderEndpoints, ProxyIdentity, ResponsesConfig, McpConfig, AsyncConfig, EndpointRoutingConfig, ClientSigningConfig, ClaimConfig } from "./types.js";

/** Environment variable keys that override YAML values. */
const ENV = {
  PORT: "ZCODE_PROXY_PORT",
  PROXY_API_KEY: "ZCODE_PROXY_API_KEY",
  PROVIDER: "ZCODE_PROVIDER",
  APP_VERSION: "ZCODE_APP_VERSION",
  SOURCE_TITLE: "ZCODE_SOURCE_TITLE",
  REFERER_ORIGIN: "ZCODE_REFERER_ORIGIN",
  ASYNC_ENABLED: "ZCODE_ASYNC_ENABLED",
  ASYNC_ORIGIN: "ZCODE_ASYNC_ORIGIN",
  ASYNC_MAX_RETRIES: "ZCODE_ASYNC_MAX_RETRIES",
  ASYNC_MAX_WAIT_MS: "ZCODE_ASYNC_MAX_WAIT_MS",
  CLAIM_ENABLED: "ZCODE_CLAIM_ENABLED",
  CLAIM_AUTO: "ZCODE_CLAIM_AUTO",
  CLAIM_ORIGIN: "ZCODE_CLAIM_ORIGIN",
  CLAIM_POLL_INTERVAL_MS: "ZCODE_CLAIM_POLL_INTERVAL_MS",
  ENDPOINT_ROUTING_ENABLED: "ZCODE_ENDPOINT_ROUTING",
  CLIENT_SIGNING_ENABLED: "ZCODE_CLIENT_SIGNING",
} as const;

const DEFAULTS = {
  PORT: 8080,
  HOST: "0.0.0.0",
  PROVIDER: "zai" as const,
  PLAN: "coding-plan" as const,
  DEFAULT_MODEL: "glm-4.6",
  LOG_LEVEL: "info" as const,
  ZAI_ANTHROPIC_BASE: "https://api.z.ai/api/anthropic",
  ZAI_OPENAI_BASE: "https://api.z.ai/api/coding/paas/v4",
  BIGMODEL_ANTHROPIC_BASE: "https://open.bigmodel.cn/api/anthropic",
  BIGMODEL_OPENAI_BASE: "https://open.bigmodel.cn/api/coding/paas/v4",
  APP_VERSION: "3.11.2",
  SOURCE_TITLE: "cli",
  REFERER_ORIGIN: "https://zcode.z.ai",
  CLIENT_IDENTITY_MODE: "observe" as const,
  CLIENT_IDENTITY_TTL_SECONDS: 900,
  CLIENT_IDENTITY_MAX_SESSIONS: 1024,
  RESPONSES_ENABLED: true,
  RESPONSES_STORE_MAX_ENTRIES: 1000,
  RESPONSES_STORE_TTL_MS: 24 * 60 * 60 * 1000,
  MCP_ENABLED: true,
  MCP_WEB_SEARCH: true,
  MCP_WEB_READER: false,
  MCP_ZREAD: false,
  ASYNC_ENABLED: false,
  ASYNC_ORIGIN: "https://zcode.z.ai",
  ASYNC_POLL_INTERVAL_MS: 5000,
  ASYNC_KEEPALIVE_INTERVAL_MS: 3000,
  ASYNC_MAX_WAIT_MS: 0,
  ASYNC_MAX_RETRIES: 3,
  ASYNC_SETTLE_TIMEOUT_MS: 8000,
  ASYNC_CONTROL_TIMEOUT_MS: 15000,
  ASYNC_DEFAULT_MODEL: "",
  CLAIM_ENABLED: true,
  CLAIM_AUTO: true,
  CLAIM_ORIGIN: "https://zcode.z.ai",
  CLAIM_POLL_INTERVAL_MS: 300000,
  CLAIM_COOLDOWN_MS: 600000,
  CLAIM_PLAN_ID: "",
  ENDPOINT_ROUTING_ENABLED: true,
  ENDPOINT_ROUTING_ORIGIN: "https://zcode.z.ai",
  CLIENT_SIGNING_ENABLED: true,
  CLIENT_SIGNING_ORIGIN: "https://zcode.z.ai",
};

/** Printable-ASCII gate copied from the ZCode bundle's `rYn` helper. */
const ASCII_PRINTABLE = /^[\x20-\x7e]+$/;

/**
 * Load and validate proxy configuration from a YAML file, applying env overrides.
 * @throws Error if file not found or required fields are invalid.
 */
export function loadConfig(path: string): ProxyConfig {
  if (!existsSync(path)) {
    throw new Error(`Config file not found: ${path}`);
  }

  const raw = readFileSync(path, "utf-8");
  const parsed = parse(raw) ?? {};

  // --- server ---
  const port = resolvePort(process.env[ENV.PORT] ?? parsed?.server?.port);
  const host = typeof parsed?.server?.host === "string" ? parsed.server.host : DEFAULTS.HOST;

  // --- auth ---
  const proxyApiKey = process.env[ENV.PROXY_API_KEY] ?? parsed?.auth?.proxyApiKey;
  const oauthCredentialsPath = parsed?.auth?.oauthCredentialsPath;

  // --- provider ---
  const provider = resolveProvider(process.env[ENV.PROVIDER] ?? parsed?.provider);
  const plan = resolvePlan(parsed?.plan);

  // --- providers ---
  const zai: ProviderEndpoints = {
    anthropicBase: parsed?.providers?.zai?.anthropicBase ?? DEFAULTS.ZAI_ANTHROPIC_BASE,
    openaiBase: parsed?.providers?.zai?.openaiBase ?? DEFAULTS.ZAI_OPENAI_BASE,
  };
  const bigmodel: ProviderEndpoints = {
    anthropicBase: parsed?.providers?.bigmodel?.anthropicBase ?? DEFAULTS.BIGMODEL_ANTHROPIC_BASE,
    openaiBase: parsed?.providers?.bigmodel?.openaiBase ?? DEFAULTS.BIGMODEL_OPENAI_BASE,
  };

  // --- models ---
  const defaultModel = typeof parsed?.defaultModel === "string" ? parsed.defaultModel : DEFAULTS.DEFAULT_MODEL;
  const models = Array.isArray(parsed?.models) ? parsed.models : [defaultModel];

  // --- logging ---
  const logLevel = resolveLogLevel(parsed?.logging?.level);

  // --- identity ---
  const identity = resolveIdentity({
    appVersionEnv: process.env[ENV.APP_VERSION],
    appVersionYaml: parsed?.identity?.appVersion,
    sourceTitleEnv: process.env[ENV.SOURCE_TITLE],
    sourceTitleYaml: parsed?.identity?.sourceTitle,
    refererEnv: process.env[ENV.REFERER_ORIGIN],
    refererYaml: parsed?.identity?.refererOrigin,
    deviceMidYaml: parsed?.identity?.deviceMid,
  });

  const clientIdentity = resolveClientIdentity(parsed?.clientIdentity);
  const responses = resolveResponsesConfig(parsed?.responses);
  const mcp = resolveMcpConfig(parsed?.mcp);
  const asyncCfg = resolveAsyncConfig(parsed?.async);
  const claimCfg = resolveClaimConfig(parsed?.claim);
  const endpointRouting = resolveEndpointRoutingConfig(parsed?.endpointRouting);
  const clientSigning = resolveClientSigningConfig(parsed?.clientSigning);

  const config: ProxyConfig = {
    server: { port, host },
    auth: { proxyApiKey, oauthCredentialsPath },
    provider,
    plan,
    providers: { zai, bigmodel },
    defaultModel,
    models,
    identity,
    clientIdentity,
    responses,
    endpointRouting,
    clientSigning,
    mcp,
    async: asyncCfg,
    claim: claimCfg,
    logging: { level: logLevel },
  };

  validate(config);
  return config;
}

function resolveClientIdentity(raw: unknown): ClientIdentityConfig {
  const obj = raw && typeof raw === "object" ? raw as Record<string, unknown> : {};
  const mode = resolveClientIdentityMode(obj.mode);
  const ttlSeconds = resolvePositiveInt(obj.ttlSeconds, DEFAULTS.CLIENT_IDENTITY_TTL_SECONDS, "clientIdentity.ttlSeconds");
  const maxSessions = resolvePositiveInt(obj.maxSessions, DEFAULTS.CLIENT_IDENTITY_MAX_SESSIONS, "clientIdentity.maxSessions");
  return { mode, ttlSeconds, maxSessions };
}

function resolveClientIdentityMode(raw: unknown): ClientIdentityConfig["mode"] {
  if (raw === undefined || raw === null) return DEFAULTS.CLIENT_IDENTITY_MODE;
  if (raw === "off" || raw === "observe" || raw === "enforce") return raw;
  throw new Error(`Invalid clientIdentity.mode "${String(raw)}": must be "off", "observe", or "enforce"`);
}

function resolveResponsesConfig(raw: unknown): ResponsesConfig {
  const obj = raw && typeof raw === "object" ? raw as Record<string, unknown> : {};
  const storeRaw = obj.store && typeof obj.store === "object" ? obj.store as Record<string, unknown> : {};
  return {
    enabled: resolveBool(obj.enabled, DEFAULTS.RESPONSES_ENABLED),
    storeMaxEntries: resolvePositiveInt(storeRaw.maxEntries, DEFAULTS.RESPONSES_STORE_MAX_ENTRIES, "responses.store.maxEntries"),
    storeTtlMs: resolvePositiveInt(storeRaw.ttlMs, DEFAULTS.RESPONSES_STORE_TTL_MS, "responses.store.ttlMs"),
  };
}

function resolveMcpConfig(raw: unknown): McpConfig {
  const obj = raw && typeof raw === "object" ? raw as Record<string, unknown> : {};
  return {
    enabled: resolveBool(obj.enabled, DEFAULTS.MCP_ENABLED),
    webSearch: resolveBool(obj.webSearch ?? obj.web_search, DEFAULTS.MCP_WEB_SEARCH),
    webReader: resolveBool(obj.webReader ?? obj.web_reader, DEFAULTS.MCP_WEB_READER),
    zread: resolveBool(obj.zread, DEFAULTS.MCP_ZREAD),
  };
}

function resolveAsyncConfig(raw: unknown): AsyncConfig {
  const obj = raw && typeof raw === "object" ? raw as Record<string, unknown> : {};
  const enabledEnv = process.env[ENV.ASYNC_ENABLED];
  const originEnv = process.env[ENV.ASYNC_ORIGIN];
  const maxRetriesEnv = process.env[ENV.ASYNC_MAX_RETRIES];
  const maxWaitMsEnv = process.env[ENV.ASYNC_MAX_WAIT_MS];

  const origin = (originEnv ?? (typeof obj.origin === "string" ? obj.origin : DEFAULTS.ASYNC_ORIGIN)).trim() || DEFAULTS.ASYNC_ORIGIN;
  validateOrigin(origin, "async.origin");

  return {
    enabled: enabledEnv !== undefined ? resolveBool(enabledEnv, DEFAULTS.ASYNC_ENABLED) : resolveBool(obj.enabled, DEFAULTS.ASYNC_ENABLED),
    origin,
    pollIntervalMs: resolvePositiveInt(obj.pollIntervalMs ?? obj.poll_interval_ms, DEFAULTS.ASYNC_POLL_INTERVAL_MS, "async.pollIntervalMs"),
    keepAliveIntervalMs: resolvePositiveInt(obj.keepAliveIntervalMs ?? obj.keepalive_interval_ms, DEFAULTS.ASYNC_KEEPALIVE_INTERVAL_MS, "async.keepAliveIntervalMs"),
    maxWaitMs: resolveNonNegativeInt(maxWaitMsEnv ?? obj.maxWaitMs ?? obj.max_wait_ms, DEFAULTS.ASYNC_MAX_WAIT_MS, "async.maxWaitMs"),
    maxRetries: resolveNonNegativeInt(maxRetriesEnv ?? obj.maxRetries ?? obj.max_retries, DEFAULTS.ASYNC_MAX_RETRIES, "async.maxRetries"),
    settleTimeoutMs: resolvePositiveInt(obj.settleTimeoutMs ?? obj.settle_timeout_ms, DEFAULTS.ASYNC_SETTLE_TIMEOUT_MS, "async.settleTimeoutMs"),
    controlTimeoutMs: resolvePositiveInt(obj.controlTimeoutMs ?? obj.control_timeout_ms, DEFAULTS.ASYNC_CONTROL_TIMEOUT_MS, "async.controlTimeoutMs"),
    defaultModel: typeof obj.defaultModel === "string" ? obj.defaultModel : DEFAULTS.ASYNC_DEFAULT_MODEL,
  };
}

function validateOrigin(origin: string, name: string): void {
  let parsed: URL;
  try {
    parsed = new URL(origin);
  } catch {
    throw new Error(`${name} "${origin}" is not a valid URL`);
  }
  // Scheme allowlist: only http/https. Other schemes (ftp:, file:, etc.) rejected.
  if (parsed.protocol !== "https:" && parsed.protocol !== "http:") {
    throw new Error(`${name} must use http: or https: scheme (got ${parsed.protocol})`);
  }
  // Cleartext HTTP only for loopback (dev/mock mode). Real off-peak backend requires
  // HTTPS — cleartext would leak the JWT + coding-plan API key to any network observer.
  const hostname = parsed.hostname.replace(/^\[|\]$/g, ""); // strip IPv6 brackets
  const isLoopback = hostname === "127.0.0.1" || hostname === "localhost" || hostname === "::1";
  if (parsed.protocol === "http:" && !isLoopback) {
    throw new Error(`${name} http:// is only allowed for loopback hosts (got ${hostname}). Use https:// for remote origins.`);
  }
  if (parsed.username || parsed.password) {
    throw new Error(`${name} must not contain userinfo`);
  }
  if (parsed.hash) {
    throw new Error(`${name} must not contain a fragment`);
  }
  if (parsed.pathname !== "/" && parsed.pathname !== "") {
    throw new Error(`${name} must not contain a path (got "${parsed.pathname}"); clients append their own paths`);
  }
  if (parsed.search) {
    throw new Error(`${name} must not contain a query string`);
  }
}

function resolveEndpointRoutingConfig(raw: unknown): EndpointRoutingConfig {
  const obj = raw && typeof raw === "object" ? raw as Record<string, unknown> : {};
  const enabledEnv = process.env[ENV.ENDPOINT_ROUTING_ENABLED];
  const origin = (typeof obj.origin === "string" ? obj.origin : DEFAULTS.ENDPOINT_ROUTING_ORIGIN).trim()
    || DEFAULTS.ENDPOINT_ROUTING_ORIGIN;
  validateOrigin(origin, "endpointRouting.origin");
  return {
    enabled: enabledEnv !== undefined ? resolveBool(enabledEnv, DEFAULTS.ENDPOINT_ROUTING_ENABLED) : resolveBool(obj.enabled, DEFAULTS.ENDPOINT_ROUTING_ENABLED),
    origin,
  };
}

function resolveClientSigningConfig(raw: unknown): ClientSigningConfig {
  const obj = raw && typeof raw === "object" ? raw as Record<string, unknown> : {};
  const enabledEnv = process.env[ENV.CLIENT_SIGNING_ENABLED];
  const origin = (typeof obj.origin === "string" ? obj.origin : DEFAULTS.CLIENT_SIGNING_ORIGIN).trim()
    || DEFAULTS.CLIENT_SIGNING_ORIGIN;
  validateOrigin(origin, "clientSigning.origin");
  return {
    enabled: enabledEnv !== undefined ? resolveBool(enabledEnv, DEFAULTS.CLIENT_SIGNING_ENABLED) : resolveBool(obj.enabled, DEFAULTS.CLIENT_SIGNING_ENABLED),
    origin,
  };
}

function resolveBool(raw: unknown, fallback: boolean): boolean {
  if (typeof raw === "boolean") return raw;
  if (typeof raw === "string") return raw === "true" || raw === "1";
  return fallback;
}

function resolvePositiveInt(raw: unknown, fallback: number, name: string): number {
  if (raw === undefined || raw === null) return fallback;
  const n = typeof raw === "number" ? raw : parseInt(String(raw), 10);
  if (!Number.isInteger(n) || n < 1) {
    throw new Error(`${name} must be a positive integer`);
  }
  return n;
}

function resolveNonNegativeInt(raw: unknown, fallback: number, name: string): number {
  if (raw === undefined || raw === null) return fallback;
  const n = typeof raw === "number" ? raw : parseInt(String(raw), 10);
  if (!Number.isInteger(n) || n < 0) {
    throw new Error(`${name} must be a non-negative integer`);
  }
  return n;
}

/** Resolve port from raw value (YAML or env), defaulting to 8080. */
function resolvePort(raw: unknown): number {
  if (raw === undefined || raw === null) return DEFAULTS.PORT;
  const n = typeof raw === "number" ? raw : parseInt(String(raw), 10);
  if (!Number.isFinite(n)) {
    throw new Error("server.port must be a valid number");
  }
  return n;
}

/** Resolve and validate provider string. */
function resolveProvider(raw: unknown): "zai" | "bigmodel" {
  const v = typeof raw === "string" ? raw : DEFAULTS.PROVIDER;
  if (v !== "zai" && v !== "bigmodel") {
    throw new Error(`Invalid provider "${v}": must be "zai" or "bigmodel"`);
  }
  return v;
}

/**
 * Resolve and validate the plan tier. Mirrors `resolveProvider`'s hard
 * validation style: an unrecognized value (e.g. `start_plan`/`startplan`
 * typos) THROWS instead of silently falling back to coding-plan — a silent
 * fallback sent users to the wrong upstream (401/403, no captcha/quota flow)
 * with nothing pointing at the config typo.
 */
function resolvePlan(raw: unknown): "coding-plan" | "start-plan" {
  if (raw === undefined || raw === null) return DEFAULTS.PLAN;
  if (raw === "coding-plan" || raw === "start-plan") return raw;
  throw new Error(`Invalid plan "${String(raw)}": must be "coding-plan" or "start-plan"`);
}

/** Resolve log level with fallback. */
function resolveLogLevel(raw: unknown): "debug" | "info" | "warn" | "error" {
  const levels = ["debug", "info", "warn", "error"] as const;
  if (typeof raw === "string" && (levels as readonly string[]).includes(raw)) {
    return raw as "debug" | "info" | "warn" | "error";
  }
  return DEFAULTS.LOG_LEVEL;
}

interface IdentityInputs {
  appVersionEnv?: string;
  appVersionYaml?: string;
  sourceTitleEnv?: string;
  sourceTitleYaml?: string;
  refererEnv?: string;
  refererYaml?: string;
  deviceMidYaml?: string;
}

/** Resolve identity fields (env > YAML > default). Non-ASCII `appVersion` silently falls back to the default. */
function resolveIdentity(inp: IdentityInputs): ProxyIdentity {
  const rawVersion = (inp.appVersionEnv ?? inp.appVersionYaml ?? DEFAULTS.APP_VERSION).trim();
  const appVersion = ASCII_PRINTABLE.test(rawVersion) ? rawVersion : DEFAULTS.APP_VERSION;

  const sourceTitle = (inp.sourceTitleEnv ?? inp.sourceTitleYaml ?? DEFAULTS.SOURCE_TITLE).trim()
    || DEFAULTS.SOURCE_TITLE;

  const refererOrigin = (inp.refererEnv ?? inp.refererYaml ?? DEFAULTS.REFERER_ORIGIN).trim()
    || DEFAULTS.REFERER_ORIGIN;

  const deviceMid = typeof inp.deviceMidYaml === "string" ? inp.deviceMidYaml.trim() : "";
  return { appVersion, sourceTitle, refererOrigin, ...(deviceMid ? { deviceMid } : {}) };
}

/** Cross-field validation after all fields are resolved. */
function resolveClaimConfig(raw: unknown): ClaimConfig {
  const obj = raw && typeof raw === "object" ? raw as Record<string, unknown> : {};
  const enabledEnv = process.env[ENV.CLAIM_ENABLED];
  const autoEnv = process.env[ENV.CLAIM_AUTO];
  const originEnv = process.env[ENV.CLAIM_ORIGIN];
  const pollIntervalEnv = process.env[ENV.CLAIM_POLL_INTERVAL_MS];

  const origin = (originEnv ?? (typeof obj.origin === "string" ? obj.origin : DEFAULTS.CLAIM_ORIGIN)).trim() || DEFAULTS.CLAIM_ORIGIN;
  validateOrigin(origin, "claim.origin");

  return {
    enabled: enabledEnv !== undefined ? resolveBool(enabledEnv, DEFAULTS.CLAIM_ENABLED) : resolveBool(obj.enabled, DEFAULTS.CLAIM_ENABLED),
    auto: autoEnv !== undefined ? resolveBool(autoEnv, DEFAULTS.CLAIM_AUTO) : resolveBool(obj.auto, DEFAULTS.CLAIM_AUTO),
    origin,
    pollIntervalMs: resolvePositiveInt(pollIntervalEnv ?? obj.pollIntervalMs ?? obj.poll_interval_ms, DEFAULTS.CLAIM_POLL_INTERVAL_MS, "claim.pollIntervalMs"),
    cooldownMs: resolvePositiveInt(obj.cooldownMs ?? obj.cooldown_ms, DEFAULTS.CLAIM_COOLDOWN_MS, "claim.cooldownMs"),
    planId: typeof obj.planId === "string" ? obj.planId.trim() : DEFAULTS.CLAIM_PLAN_ID,
  };
}

function validate(config: ProxyConfig): void {
  if (config.server.port < 1 || config.server.port > 65535) {
    throw new Error(`server.port ${config.server.port} is out of range (1-65535)`);
  }

  if (!config.models.includes(config.defaultModel)) {
    // defaultModel not in the models list — add it automatically
    config.models.push(config.defaultModel);
  }
}