import fs from "node:fs/promises";
import path from "node:path";

import { type ClawdbotConfig, loadConfig } from "../config/config.js";
import {
  DEFAULT_COPILOT_API_BASE_URL,
  resolveCopilotApiToken,
} from "../providers/github-copilot-token.js";
import { resolveClawdbotAgentDir } from "./agent-paths.js";
import {
  ensureAuthProfileStore,
  listProfilesForProvider,
} from "./auth-profiles.js";
import {
  normalizeProviders,
  type ProviderConfig,
  resolveImplicitProviders,
} from "./models-config.providers.js";

type ModelsConfig = NonNullable<ClawdbotConfig["models"]>;

const DEFAULT_MODE: NonNullable<ModelsConfig["mode"]> = "merge";

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

function mergeProviderModels(
  implicit: ProviderConfig,
  explicit: ProviderConfig,
): ProviderConfig {
  const implicitModels = Array.isArray(implicit.models) ? implicit.models : [];
  const explicitModels = Array.isArray(explicit.models) ? explicit.models : [];
  if (implicitModels.length === 0) return { ...implicit, ...explicit };

  const getId = (model: unknown): string => {
    if (!model || typeof model !== "object") return "";
    const id = (model as { id?: unknown }).id;
    return typeof id === "string" ? id.trim() : "";
  };
  const seen = new Set(explicitModels.map(getId).filter(Boolean));

  const mergedModels = [
    ...explicitModels,
    ...implicitModels.filter((model) => {
      const id = getId(model);
      if (!id) return false;
      if (seen.has(id)) return false;
      seen.add(id);
      return true;
    }),
  ];

  return {
    ...implicit,
    ...explicit,
    models: mergedModels,
  };
}

function mergeProviders(params: {
  implicit?: Record<string, ProviderConfig> | null;
  explicit?: Record<string, ProviderConfig> | null;
}): Record<string, ProviderConfig> {
  const out: Record<string, ProviderConfig> = params.implicit
    ? { ...params.implicit }
    : {};
  for (const [key, explicit] of Object.entries(params.explicit ?? {})) {
    const providerKey = key.trim();
    if (!providerKey) continue;
    const implicit = out[providerKey];
    out[providerKey] = implicit
      ? mergeProviderModels(implicit, explicit)
      : explicit;
  }
  return out;
}

async function readJson(pathname: string): Promise<unknown> {
  try {
    const raw = await fs.readFile(pathname, "utf8");
    return JSON.parse(raw) as unknown;
  } catch {
    return null;
  }
}

async function maybeBuildCopilotProvider(params: {
  agentDir: string;
  env?: NodeJS.ProcessEnv;
}): Promise<ProviderConfig | null> {
  const env = params.env ?? process.env;
  const authStore = ensureAuthProfileStore(params.agentDir);
  const hasProfile =
    listProfilesForProvider(authStore, "github-copilot").length > 0;
  const envToken = env.COPILOT_GITHUB_TOKEN ?? env.GH_TOKEN ?? env.GITHUB_TOKEN;
  const githubToken = (envToken ?? "").trim();

  if (!hasProfile && !githubToken) return null;

  let selectedGithubToken = githubToken;
  if (!selectedGithubToken && hasProfile) {
    // Use the first available profile as a default for discovery (it will be
    // re-resolved per-run by the embedded runner).
    const profileId = listProfilesForProvider(authStore, "github-copilot")[0];
    const profile = profileId ? authStore.profiles[profileId] : undefined;
    if (profile && profile.type === "token") {
      selectedGithubToken = profile.token;
    }
  }

  let baseUrl = DEFAULT_COPILOT_API_BASE_URL;
  if (selectedGithubToken) {
    try {
      const token = await resolveCopilotApiToken({
        githubToken: selectedGithubToken,
        env,
      });
      baseUrl = token.baseUrl;
    } catch {
      baseUrl = DEFAULT_COPILOT_API_BASE_URL;
    }
  }

  // pi-coding-agent's ModelRegistry marks a model "available" only if its
  // `AuthStorage` has auth configured for that provider (via auth.json/env/etc).
  // Our Copilot auth lives in Clawdbot's auth-profiles store instead, so we also
  // write a runtime-only auth.json entry for pi-coding-agent to pick up.
  //
  // This is safe because it's (1) within Clawdbot's agent dir, (2) contains the
  // GitHub token (not the exchanged Copilot token), and (3) matches existing
  // patterns for OAuth-like providers in pi-coding-agent.
  // Note: we deliberately do not write pi-coding-agent's `auth.json` here.
  // Clawdbot uses its own auth store and exchanges tokens at runtime.
  // `models list` uses Clawdbot's auth heuristics for availability.

  // We intentionally do NOT define custom models for Copilot in models.json.
  // pi-coding-agent treats providers with models as replacements requiring apiKey.
  // We only override baseUrl; the model list comes from pi-ai built-ins.
  return {
    baseUrl,
    models: [],
  } satisfies ProviderConfig;
}

export async function ensureClawdbotModelsJson(
  config?: ClawdbotConfig,
  agentDirOverride?: string,
): Promise<{ agentDir: string; wrote: boolean }> {
  const cfg = config ?? loadConfig();
  const agentDir = agentDirOverride?.trim()
    ? agentDirOverride.trim()
    : resolveClawdbotAgentDir();

  const explicitProviders = (cfg.models?.providers ?? {}) as Record<
    string,
    ProviderConfig
  >;
  const implicitProviders = resolveImplicitProviders({ agentDir });
  const providers: Record<string, ProviderConfig> = mergeProviders({
    implicit: implicitProviders,
    explicit: explicitProviders,
  });
  const implicitCopilot = await maybeBuildCopilotProvider({ agentDir });
  if (implicitCopilot && !providers["github-copilot"]) {
    providers["github-copilot"] = implicitCopilot;
  }

  if (Object.keys(providers).length === 0) {
    return { agentDir, wrote: false };
  }

  const mode = cfg.models?.mode ?? DEFAULT_MODE;
  const targetPath = path.join(agentDir, "models.json");

  let mergedProviders = providers;
  let existingRaw = "";
  if (mode === "merge") {
    const existing = await readJson(targetPath);
    if (isRecord(existing) && isRecord(existing.providers)) {
      const existingProviders = existing.providers as Record<
        string,
        NonNullable<ModelsConfig["providers"]>[string]
      >;
      mergedProviders = { ...existingProviders, ...providers };
    }
  }

  const normalizedProviders = normalizeProviders({
    providers: mergedProviders,
    agentDir,
  });
  const next = `${JSON.stringify({ providers: normalizedProviders }, null, 2)}\n`;
  try {
    existingRaw = await fs.readFile(targetPath, "utf8");
  } catch {
    existingRaw = "";
  }

  if (existingRaw === next) {
    return { agentDir, wrote: false };
  }

  await fs.mkdir(agentDir, { recursive: true, mode: 0o700 });
  await fs.writeFile(targetPath, next, { mode: 0o600 });
  return { agentDir, wrote: true };
}