// The AI assistant's wire client. `local`/`public` mirror vncmail-native's
// src/api/ai.ts (direct loopback/provider fetch, no streaming) so the two
// clients stay in lockstep — matching docs/AI-ASSISTANT-CONCEPT.md §2's
// "local"/"public" rows, not proxied through this app's own Next.js server.
// That distinction matters once this app is hosted remotely: a server-side
// proxy would reach the *server's* loopback, not the user's own laptop
// running Ollama.
//
// `server` (added 2026-08-05 night) is the opposite by design: it DOES
// proxy through this app's own backend (app/api/ai/server/*), because it's
// centrally-hosted infra (VNC's EU/CH stack — standing in tonight for a real
// Ollama on this Mac, see lib/ai/entitlement.ts), not a user's own machine.
// That server-side hop is also the one real entitlement enforcement point
// (§10 point 2) — `local`/`public` never reach it, by design, and so cannot
// be metered or billed the same way.

export interface ChatMessage {
  role: 'system' | 'user' | 'assistant';
  content: string;
}

// ── Local: Ollama's native API, not the OpenAI-compat shim — one fewer path
// assumption (no "/v1" prefix to guess at) for a runtime this code talks to directly. ──

interface OllamaTagsResponse {
  models?: Array<{ name: string }>;
}

interface OllamaChatResponse {
  message?: { content?: string };
}

export async function listLocalModels(baseUrl: string): Promise<string[]> {
  const res = await fetch(`${baseUrl.replace(/\/+$/, '')}/api/tags`);
  if (!res.ok) throw new Error(`Ollama returned ${res.status}`);
  const body = (await res.json()) as OllamaTagsResponse;
  return (body.models ?? []).map((m) => m.name).filter(Boolean);
}

/**
 * Diagnoses the specific failure rather than a generic "connection failed" —
 * docs/AI-ASSISTANT-CONCEPT.md §3 calls this out explicitly for the browser
 * row: a CORS rejection (the runtime is up but refused this page's origin)
 * looks identical to "nothing is listening" unless told apart. `fetch`
 * itself can't distinguish them (a CORS failure and a connection refusal
 * both surface as `TypeError: Failed to fetch`), so this only upgrades the
 * message when the caller can tell us there's a live page origin to name.
 */
export async function testLocalConnection(
  baseUrl: string,
): Promise<{ ok: boolean; error?: string }> {
  try {
    await listLocalModels(baseUrl);
    return { ok: true };
  } catch (err) {
    const origin = typeof window !== 'undefined' ? window.location.origin : null;
    const hint = origin
      ? ` Reachable in principle, but if Ollama is actually running, it likely refused this page's origin (${origin}) — start it with OLLAMA_ORIGINS=${origin}.`
      : '';
    return {
      ok: false,
      error: (err instanceof Error ? err.message : String(err)) + hint,
    };
  }
}

export async function chatLocal(
  baseUrl: string,
  model: string,
  messages: ChatMessage[],
): Promise<string> {
  const res = await fetch(`${baseUrl.replace(/\/+$/, '')}/api/chat`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ model, messages, stream: false }),
  });
  if (!res.ok) throw new Error(`Ollama returned ${res.status}`);
  const body = (await res.json()) as OllamaChatResponse;
  const content = body.message?.content;
  if (!content) throw new Error('Ollama returned no message content');
  return content;
}

// ── Server: centrally-hosted, proxied through this app's own backend
// (app/api/ai/server/*). Unlike `local`, this is same-origin from the
// browser's perspective — no CORS/OLLAMA_ORIGINS story at all — and unlike
// both `local` and `public`, every call is entitlement-checked server-side. ──

export async function listServerModels(): Promise<string[]> {
  const res = await fetch('/api/ai/server/models');
  if (!res.ok) {
    const body = (await res.json().catch(() => null)) as { error?: string } | null;
    throw new Error(body?.error ?? `AI server returned ${res.status}`);
  }
  const body = (await res.json()) as { models?: string[] };
  return body.models ?? [];
}

export interface ServerChatResult {
  answer: string;
  /** True the moment this call consumed a previously-unassigned licensed seat
   *  (lib/ai/entitlement.ts) — surfaced so the UI can say so once, not left
   *  to happen silently the first time someone uses this class. */
  seatJustAssigned: boolean;
}

export async function chatServer(model: string, messages: ChatMessage[]): Promise<ServerChatResult> {
  const res = await fetch('/api/ai/server/chat', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ model, messages }),
  });
  const body = (await res.json().catch(() => null)) as { answer?: string; error?: string; seatJustAssigned?: boolean } | null;
  if (!res.ok || !body?.answer) {
    throw new Error(body?.error ?? `AI server returned ${res.status}`);
  }
  return { answer: body.answer, seatJustAssigned: body.seatJustAssigned === true };
}

// ── Public: OpenAI-compatible chat-completions. OpenRouter by default, but any
// endpoint speaking this shape works unmodified (self-hosted vLLM, LiteLLM, etc). ──

interface OpenAiChatResponse {
  choices?: Array<{ message?: { content?: string } }>;
}

export async function chatPublic(
  baseUrl: string,
  apiKey: string,
  model: string,
  messages: ChatMessage[],
): Promise<string> {
  const res = await fetch(`${baseUrl.replace(/\/+$/, '')}/chat/completions`, {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      Authorization: `Bearer ${apiKey}`,
    },
    body: JSON.stringify({ model, messages }),
  });
  if (!res.ok) throw new Error(`Provider returned ${res.status}`);
  const body = (await res.json()) as OpenAiChatResponse;
  const content = body.choices?.[0]?.message?.content;
  if (!content) throw new Error('Provider returned no message content');
  return content;
}

// ── Retrieval: this app's own already-built offline search surface
// (app/api/offline/search/route.ts), not a client-side index — the
// encrypted SQLite/FTS5 store it reads only exists in Electron's main
// process. A 404/503 there means "no index in this session", not an error:
// degrade to an unaugmented chat rather than fail the question. ──

export interface AskSource {
  id: string;
  subject: string;
}

export interface AskResult {
  answer: string;
  sources: AskSource[];
  /** True when the question was answered without any retrieved context. */
  unaugmented: boolean;
  /** True the moment this call consumed a previously-unassigned licensed
   *  seat on the `server` class (lib/ai/entitlement.ts). Always false for
   *  `local`/`public`, which aren't entitlement-gated. */
  seatJustAssigned: boolean;
}

interface OfflineSearchHit {
  id: string;
  title: string;
  snippet?: string;
}

interface OfflineSearchResponse {
  ok: true;
  hits: OfflineSearchHit[];
  contextBlock: string;
}

async function retrieveContext(question: string): Promise<OfflineSearchResponse | null> {
  const res = await fetch(`/api/offline/search?q=${encodeURIComponent(question)}&limit=6`);
  if (!res.ok) return null; // 404 (no index configured) or 503 (unavailable this session) — both mean "no retrieval", not an error
  const body = (await res.json()) as OfflineSearchResponse;
  return body.ok ? body : null;
}

export function buildPrompt(question: string, contextBlock: string): ChatMessage[] {
  return [
    {
      role: 'system',
      content:
        "You answer questions about the user's email using only the numbered excerpts " +
        'below as context. Cite sources by their number in brackets, e.g. [1]. If the ' +
        "excerpts don't contain the answer, say so plainly rather than guessing.",
    },
    { role: 'user', content: `${contextBlock}\n\nQuestion: ${question}` },
  ];
}

/**
 * One saved BYOK profile, resolved to an actual key — the caller picks which
 * profile answers *this* question (docs decision 2026-08-05: several keys,
 * selected case by case, not one fixed "the" public provider).
 */
export interface ResolvedPublicProfile {
  baseUrl: string;
  model: string;
  apiKey: string;
}

export interface AskConfig {
  provider: 'local' | 'server' | 'public';
  localBaseUrl: string;
  localModel: string | null;
  serverModel: string | null;
  publicProfile: ResolvedPublicProfile | null;
}

export async function askMail(question: string, config: AskConfig): Promise<AskResult> {
  if (config.provider === 'local' && !config.localModel) {
    throw new Error('No local model selected');
  }
  if (config.provider === 'server' && !config.serverModel) {
    throw new Error('No server model selected');
  }
  if (config.provider === 'public' && !config.publicProfile) {
    throw new Error('No provider profile selected');
  }

  const retrieved = await retrieveContext(question);
  const messages = retrieved
    ? buildPrompt(question, retrieved.contextBlock)
    : [{ role: 'user' as const, content: question }];

  let answer: string;
  let seatJustAssigned = false;
  if (config.provider === 'public') {
    const profile = config.publicProfile as ResolvedPublicProfile;
    answer = await chatPublic(profile.baseUrl, profile.apiKey, profile.model, messages);
  } else if (config.provider === 'server') {
    const result = await chatServer(config.serverModel as string, messages);
    answer = result.answer;
    seatJustAssigned = result.seatJustAssigned;
  } else {
    answer = await chatLocal(config.localBaseUrl, config.localModel as string, messages);
  }

  return {
    answer,
    sources: (retrieved?.hits ?? []).map((h) => ({ id: h.id, subject: h.title })),
    unaugmented: !retrieved,
    seatJustAssigned,
  };
}