/**
 * AI settings service — the runtime source of truth for which LLM the
 * processor talks to.
 *
 * Why this exists
 * ───────────────
 * Before this service the quotes-ai-processor read `process.env.ANTHROPIC_API_KEY`
 * and shipped every Claude call at a fixed provider/model. That was fine
 * for one developer with one key on one machine. It breaks for:
 *
 *   • Key rotation — would force a redeploy each time.
 *   • Multi-provider support — MiniMax / Anthropic-direct selection has
 *     to happen at call time, not via env-var juggling.
 *   • Operator visibility — the UI needs to surface "is the AI on?"
 *     (the `enabled` killswitch) without grepping `.env.local`.
 *
 * Contract
 * ────────
 *   • Single-row table. `ai_settings` is a PocketBase collection with at
 *     most one row; `getAiSettings()` returns that row (or a synthetic
 *     default if the row is missing entirely).
 *   • 60-second in-memory cache. UI refreshes within a minute of an
 *     update; the AI processor hot-path pays at most one PB read per
 *     minute.
 *   • `api_key` is gated by `isSuperuser()`. Routes that don't have an
 *     admin context (the /settings/ai page) get back a redacted record
 *     with `api_key: ""` and `api_key_set: boolean` instead. The
 *     processor (server-side, admin PB) always gets the full value.
 *   • Plain-text by design — the operator explicitly chose visibility
 *     over encryption-at-rest on 2026-08-09. Don't add encryption here
 *     without re-checking with them.
 */
import { getAdminPocketBase } from "./pocketbase-admin";

export type AiProvider = "anthropic" | "minimax";

/**
 * The shape returned by the read path. Mirrors the PB row 1:1 plus
 * a derived `api_key_set` flag (so we can tell the UI "a key is set"
 * without leaking the value itself).
 */
export interface AiSettings {
  id: string;
  provider: AiProvider | "";
  api_key: string;
  api_key_set: boolean;
  base_url: string;
  model_id: string;
  max_tokens: number;
  enabled: boolean;
  /**
   * Operator-editable override of the system prompt sent to the
   * Anthropic API. Empty string means "use the hardcoded default in
   * the source" — see `src/lib/server/ai-system-prompt.ts`. The
   * processor reads this via `getAiSettings()` (cached, 60s TTL).
   */
  system_prompt: string;
  updated_at: string;
}

/**
 * The shape returned to write paths. `api_key` here is OPTIONAL — when
 * omitted on a PUT the existing key is preserved (the UI sends an empty
 * string to clear).
 */
export interface AiSettingsUpdate {
  provider?: AiProvider | "";
  api_key?: string;
  base_url?: string;
  model_id?: string;
  max_tokens?: number;
  enabled?: boolean;
  /**
   * Operator-editable system prompt override. `undefined` ⇒ no change.
   * `""` ⇒ clear override (processor falls back to default). Non-empty
   * ⇒ processor uses this verbatim. Length capped at 50 000 chars
   * (matches the PB field's `options.max`).
   */
  system_prompt?: string;
}

const COLLECTION = "ai_settings";

/** Defaults used when the PB row is absent (first boot, before the
 *  migration has run). Matches the migration's seed row. */
const DEFAULT_SETTINGS: AiSettings = {
  id: "",
  provider: "minimax",
  api_key: "",
  api_key_set: false,
  base_url: "https://api.minimax.io/anthropic",
  model_id: "MiniMax-M3",
  max_tokens: 4096,
  enabled: false,
  system_prompt: "",
  updated_at: "",
};

/** TTL is short enough that a UI refresh after an update sees the new
 *  state, but long enough that the processor (which may fire many times
 *  in a row) doesn't hit PB on every call. */
const CACHE_TTL_MS = 60_000;

interface CacheEntry {
  record: AiSettings;
  expiresAt: number;
}

let cache: CacheEntry | null = null;

interface RawSettingsRow {
  id: string;
  provider?: string;
  api_key?: string;
  base_url?: string;
  model_id?: string;
  max_tokens?: number;
  enabled?: boolean;
  system_prompt?: string;
  updated_at?: string;
}

function normaliseProvider(value: unknown): AiProvider | "" {
  if (value === "anthropic" || value === "minimax") return value;
  return "";
}

function rowToSettings(row: RawSettingsRow): AiSettings {
  return {
    id: row.id,
    provider: normaliseProvider(row.provider),
    api_key: row.api_key ?? "",
    api_key_set: !!(row.api_key && row.api_key.length > 0),
    base_url: row.base_url ?? "",
    model_id: row.model_id ?? "",
    max_tokens: typeof row.max_tokens === "number" ? row.max_tokens : 4096,
    enabled: !!row.enabled,
    system_prompt: row.system_prompt ?? "",
    updated_at: row.updated_at ?? "",
  };
}

/** Used in tests to force a fresh read after an out-of-band PB write. */
export function clearAiSettingsCache(): void {
  cache = null;
}

function cacheGet(): AiSettings | null {
  if (!cache) return null;
  if (cache.expiresAt <= Date.now()) {
    cache = null;
    return null;
  }
  return cache.record;
}

function cacheSet(record: AiSettings): void {
  cache = { record, expiresAt: Date.now() + CACHE_TTL_MS };
}

/**
 * Read the single AI-settings row. Returns the redacted shape by
 * default (api_key="" + api_key_set=boolean) so callers that shouldn't
 * see the key can't accidentally surface it. Pass `includeSecret: true`
 * from server-side admin contexts (e.g. the AI processor).
 *
 * Falls back to DEFAULT_SETTINGS when no row exists yet, so callers
 * don't have to handle a missing-row case in their own code paths.
 */
export async function getAiSettings(
  options: { includeSecret?: boolean } = {},
): Promise<AiSettings> {
  const includeSecret = options.includeSecret === true;
  const cached = cacheGet();
  if (cached) {
    return includeSecret
      ? cached
      : { ...cached, api_key: "", api_key_set: cached.api_key_set };
  }

  const pb = await getAdminPocketBase();
  let record: AiSettings;
  try {
    const rows = await pb.collection(COLLECTION).getFullList({});
    if (rows.length === 0) {
      record = { ...DEFAULT_SETTINGS };
    } else {
      // Single-row invariant — if the operator ever duplicates, take
      // the most-recently-updated so the read is at least deterministic.
      const sorted = (rows as RawSettingsRow[]).sort((a, b) => {
        const at = a.updated_at ?? "";
        const bt = b.updated_at ?? "";
        return bt.localeCompare(at);
      });
      record = rowToSettings(sorted[0]);
    }
  } catch {
    // Collection missing entirely (pre-migration). Fall back to defaults
    // rather than throw — callers like /settings/ai should still render.
    record = { ...DEFAULT_SETTINGS };
  }
  cacheSet(record);
  return includeSecret
    ? record
    : { ...record, api_key: "", api_key_set: record.api_key_set };
}

/**
 * Patch the AI-settings row. The caller passes only the fields they
 * want to change. Special handling for `api_key`:
 *
 *   • `api_key: undefined`    → field not touched.
 *   • `api_key: ""`           → field cleared (api_key_set becomes false).
 *   • `api_key: "sk-..."`     → field replaced.
 *
 * Bumps the in-memory cache on success so the very next `getAiSettings()`
 * sees the update without waiting out the TTL.
 */
export async function updateAiSettings(
  patch: AiSettingsUpdate,
): Promise<AiSettings> {
  const pb = await getAdminPocketBase();

  // Find the single row (or fall back to creating one if it doesn't
  // exist yet — first-run scenario).
  const rows = await pb.collection(COLLECTION).getFullList({});

  const dbPatch: Record<string, unknown> = {};
  if (patch.provider !== undefined) {
    if (patch.provider !== "" && patch.provider !== "anthropic" && patch.provider !== "minimax") {
      throw new Error(`Unknown provider "${patch.provider}"`);
    }
    dbPatch.provider = patch.provider || "";
  }
  if (patch.api_key !== undefined) {
    dbPatch.api_key = patch.api_key; // already "" when clearing
  }
  if (patch.base_url !== undefined) dbPatch.base_url = patch.base_url;
  if (patch.model_id !== undefined) dbPatch.model_id = patch.model_id;
  if (patch.max_tokens !== undefined) {
    if (
      typeof patch.max_tokens !== "number" ||
      !Number.isFinite(patch.max_tokens) ||
      patch.max_tokens < 256 ||
      patch.max_tokens > 8192
    ) {
      throw new Error("max_tokens must be a number between 256 and 8192");
    }
    dbPatch.max_tokens = Math.round(patch.max_tokens);
  }
  if (patch.enabled !== undefined) dbPatch.enabled = !!patch.enabled;
  if (patch.system_prompt !== undefined) {
    // Defensive cap — the PB field already enforces 50 000 but the
    // route handler is one boundary removed. Truncate rather than
    // reject so a paste-from-clipboard typo doesn't 400 the whole form.
    dbPatch.system_prompt = patch.system_prompt.slice(0, 50_000);
  }

  dbPatch.updated_at = new Date().toISOString();

  let savedRow: RawSettingsRow;
  if (rows.length === 0) {
    // First-ever write — seed with merged defaults so we never end up
    // with a row that has a missing required-like field.
    savedRow = (await pb.collection(COLLECTION).create({
      provider: "minimax",
      api_key: "",
      base_url: "https://api.minimax.io/anthropic",
      model_id: "MiniMax-M3",
      max_tokens: 4096,
      enabled: false,
      system_prompt: "",
      ...dbPatch,
    })) as RawSettingsRow;
  } else {
    const id = (rows[0] as RawSettingsRow).id;
    savedRow = (await pb.collection(COLLECTION).update(id, dbPatch)) as RawSettingsRow;
  }

  const record = rowToSettings(savedRow);
  cacheSet(record);
  return record;
}

/**
 * Convenience for callers that just want the SDK knobs (no record
 * scaffolding). Equivalent to `getAiSettings({ includeSecret: true })`
 * but with a single field-select to keep the type tight. Also raises
 * a clear error if the processor tries to run while disabled.
 */
export interface ActiveAiConfig {
  provider: AiProvider;
  apiKey: string;
  baseUrl: string;
  modelId: string;
  maxTokens: number;
}

export async function getActiveAiConfig(): Promise<ActiveAiConfig> {
  const settings = await getAiSettings({ includeSecret: true });
  if (!settings.enabled) {
    throw new AiDisabledError("AI is disabled in settings");
  }
  if (!settings.api_key) {
    throw new Error(
      `AI is enabled but api_key is not set (provider=${settings.provider || "(none)"}). Update /settings/ai.`,
    );
  }
  if (!settings.model_id) {
    throw new Error("AI is enabled but model_id is not set. Update /settings/ai.");
  }
  // For "anthropic" we let the SDK pick its default endpoint by
  // passing undefined baseURL — that keeps retries / SDK features
  // working normally. For every other provider we honour whatever
  // the operator typed (MiniMax's Anthropic-compatible endpoint in
  // particular must be set explicitly).
  const baseUrl =
    settings.provider === "anthropic"
      ? settings.base_url || undefined
      : settings.base_url;
  return {
    provider: settings.provider as AiProvider,
    apiKey: settings.api_key,
    baseUrl: baseUrl ?? "",
    modelId: settings.model_id,
    maxTokens: settings.max_tokens || 4096,
  };
}

/** Tagged error so the processor can map "AI off" to ai_error="ai_disabled". */
export class AiDisabledError extends Error {
  readonly code = "ai_disabled";
  constructor(message: string) {
    super(message);
    this.name = "AiDisabledError";
  }
}