import type { Db } from "@stc/db";
import type { SecretBox } from "./crypto";

export type ProviderKind = "anthropic" | "openai";
export type Effort = "low" | "medium" | "high" | "xhigh" | "max";
export interface ProviderConfig { kind: ProviderKind; model?: string; baseUrl?: string; effort?: Effort }
export type PublicProviderConfig = ProviderConfig & { hasApiKey: boolean };

export interface McpServerConfig {
  id: string;
  name: string;
  transport: "stdio" | "http";
  command?: string;
  args?: string[];
  env?: Record<string, string>;
  url?: string;
  headers?: Record<string, string>;
  /** Courses this server is offered in. Absent or empty: every course (global). */
  courseIds?: string[];
}

export interface ServerSettings { provider: PublicProviderConfig | null; mcpServers: McpServerConfig[] }
export interface ServerSettingsInput {
  provider: (ProviderConfig & { apiKey?: string; clearApiKey?: boolean }) | null;
  mcpServers: McpServerConfig[];
}
export interface UserSettings { byok: PublicProviderConfig | null; mentorOff: Record<string, boolean> }

type ServerRow = { provider: ProviderConfig | null; apiKeyCipher: string | null; mcpServers: McpServerConfig[] };
type UserRow = { byok: ProviderConfig | null; mentorOff: Record<string, boolean> };

const pickProvider = (p: ProviderConfig): ProviderConfig => {
  const out: ProviderConfig = { kind: p.kind };
  if (p.model) out.model = p.model;
  if (p.baseUrl) out.baseUrl = p.baseUrl;
  if (p.effort) out.effort = p.effort;
  return out;
};

const parse = <T>(s: string | undefined, fallback: T): T => {
  if (!s) return fallback;
  try { return { ...fallback, ...JSON.parse(s) }; } catch { return fallback; }
};

/**
 * AI settings in the ai_settings and user_api_keys tables of 0001_init.sql.
 * - ('server', '') holds the admin provider (key encrypted) and MCP servers.
 * - ('user', <userId>) holds the BYOK provider choice and per-course mentor toggles. The frozen primary key
 *   is (scope, owner_id), so the per-course flag lives in config_json; the mentor_off column means
 *   "off for every course" and stays 0 (see docs/contract-requests/ai.md).
 * Keys never leave this module except through serverApiKey/userApiKey, which only server code calls.
 */
export function aiSettingsRepo(db: Db, box: SecretBox) {
  const read = async (scope: "server" | "user", owner: string): Promise<string | undefined> => {
    const rows = await db.sql`SELECT config_json FROM ai_settings WHERE scope = ${scope} AND owner_id = ${owner}`;
    return rows[0]?.config_json;
  };
  const write = async (scope: "server" | "user", owner: string, value: unknown) => {
    const json = JSON.stringify(value);
    const now = new Date().toISOString();
    await db.sql.begin(async (tx) => {
      const exists = await tx`SELECT 1 AS x FROM ai_settings WHERE scope = ${scope} AND owner_id = ${owner}`;
      if (exists.length) await tx`UPDATE ai_settings SET config_json = ${json}, updated_at = ${now} WHERE scope = ${scope} AND owner_id = ${owner}`;
      else await tx`INSERT INTO ai_settings (scope, owner_id, mentor_off, config_json, updated_at) VALUES (${scope}, ${owner}, 0, ${json}, ${now})`;
    });
  };
  const serverRow = async (): Promise<ServerRow> => parse(await read("server", ""), { provider: null, apiKeyCipher: null, mcpServers: [] });
  const userRow = async (userId: string): Promise<UserRow> => parse(await read("user", userId), { byok: null, mentorOff: {} });
  const keyRow = async (userId: string) =>
    (await db.sql`SELECT provider, ciphertext FROM user_api_keys WHERE user_id = ${userId}`)[0] as { provider: string; ciphertext: string } | undefined;

  return {
    async getServer(): Promise<ServerSettings> {
      const r = await serverRow();
      return { provider: r.provider ? { ...r.provider, hasApiKey: !!r.apiKeyCipher } : null, mcpServers: r.mcpServers ?? [] };
    },
    async saveServer(input: ServerSettingsInput): Promise<void> {
      const prev = await serverRow();
      let apiKeyCipher: string | null = null;
      if (input.provider) {
        if (input.provider.apiKey) apiKeyCipher = await box.encrypt(input.provider.apiKey);
        else if (!input.provider.clearApiKey) apiKeyCipher = prev.apiKeyCipher;
      }
      await write("server", "", {
        provider: input.provider ? pickProvider(input.provider) : null,
        apiKeyCipher,
        mcpServers: input.mcpServers ?? [],
      });
    },
    async serverApiKey(): Promise<string | null> {
      const r = await serverRow();
      return r.provider && r.apiKeyCipher ? box.decrypt(r.apiKeyCipher) : null;
    },
    async getUser(userId: string): Promise<UserSettings> {
      const r = await userRow(userId);
      const k = await keyRow(userId);
      return { byok: r.byok && k ? { ...r.byok, hasApiKey: true } : null, mentorOff: r.mentorOff ?? {} };
    },
    async saveUserKey(userId: string, cfg: ProviderConfig & { apiKey: string }): Promise<void> {
      const ciphertext = await box.encrypt(cfg.apiKey);
      const now = new Date().toISOString();
      await db.sql.begin(async (tx) => {
        await tx`DELETE FROM user_api_keys WHERE user_id = ${userId}`;
        await tx`INSERT INTO user_api_keys (user_id, provider, ciphertext, created_at) VALUES (${userId}, ${cfg.kind}, ${ciphertext}, ${now})`;
      });
      const r = await userRow(userId);
      await write("user", userId, { ...r, byok: pickProvider(cfg) });
    },
    async removeUserKey(userId: string): Promise<void> {
      await db.sql`DELETE FROM user_api_keys WHERE user_id = ${userId}`;
      const r = await userRow(userId);
      await write("user", userId, { ...r, byok: null });
    },
    async userApiKey(userId: string): Promise<string | null> {
      const k = await keyRow(userId);
      return k ? box.decrypt(k.ciphertext) : null;
    },
    async setMentorOff(userId: string, courseId: string, off: boolean): Promise<void> {
      const r = await userRow(userId);
      const mentorOff = { ...r.mentorOff };
      if (off) mentorOff[courseId] = true;
      else delete mentorOff[courseId];
      await write("user", userId, { ...r, mentorOff });
    },
    async isMentorOff(userId: string, courseId: string): Promise<boolean> {
      return (await userRow(userId)).mentorOff?.[courseId] === true;
    },
  };
}

export type AiSettingsRepo = ReturnType<typeof aiSettingsRepo>;