"use client";

import { ApiError, consumeNdjson } from "./client-api";
import { localeHeader, t } from "./i18n";
import { authHeaders } from "./settings";
import { providerHeaders, providersStore } from "./providers-client";
import type { ChatSource } from "./chat";

/**
 * Client for the streaming chat route. The conversation window and the chosen
 * context chunks travel with every request (the server never stores either);
 * the API key only ever goes to our own route in its usual header.
 */

export type ChatStreamEvent =
  | { type: "token"; text: string }
  | { type: "thinking"; text: string }
  | { type: "done"; model: string }
  | { type: "error"; error: string; kind?: string };

export type StreamChatInput = {
  model?: string;
  /** A cloud provider the model belongs to (Ollama when omitted). */
  provider?: string;
  messages: { role: "user" | "assistant"; content: string }[];
  context: (ChatSource & { text: string })[];
  /** "teach" runs a Teach it back turn; "teach_summary" asks for the recap JSON. */
  mode?: "teach" | "teach_summary";
  teach?: {
    topic: string;
    difficulty: "friendly" | "skeptical";
    /** Exchanges answered so far, and how many the session plans. */
    exchange: number;
    limit: number;
    /** "[n] question → answer" checklist lines (lib/teach.ts). */
    cards: string[];
  };
  signal?: AbortSignal;
  onToken: (text: string) => void;
  onThinking: (text: string) => void;
  onDone: (model: string) => void;
};

export async function streamChat(input: StreamChatInput): Promise<void> {
  let response: Response;
  try {
    response = await fetch("/api/chat", {
      method: "POST",
      headers: { "Content-Type": "application/json", ...authHeaders(), ...providerHeaders(input.provider), ...localeHeader() },
      body: JSON.stringify({
        model: input.model || undefined,
        messages: input.messages,
        context: input.context,
        mode: input.mode,
        teach: input.teach,
      }),
      signal: input.signal,
    });
  } catch (error) {
    if (error instanceof Error && error.name === "AbortError") {
      throw new ApiError(t("api.cancelled"), "aborted");
    }
    throw new ApiError(t("api.unreachable"), "network");
  }

  if (!response.ok) {
    const body = (await response.json().catch(() => null)) as { error?: string; kind?: string } | null;
    throw new ApiError(body?.error ?? t("api.httpError", { status: response.status }), body?.kind);
  }

  let streamError: ApiError | null = null;
  try {
    await consumeNdjson(response, (raw) => {
      const event = raw as ChatStreamEvent;
      if (event.type === "token") input.onToken(event.text);
      else if (event.type === "thinking") input.onThinking(event.text);
      else if (event.type === "done") input.onDone(event.model);
      else if (event.type === "error") streamError = new ApiError(event.error, event.kind);
    });
  } catch (error) {
    // Aborting while the body is being read rejects the reader with an
    // AbortError, not a fetch rejection — treat it as a user stop.
    if (error instanceof Error && error.name === "AbortError") {
      throw new ApiError(t("api.cancelled"), "aborted");
    }
    throw error;
  }

  if (streamError) throw streamError;
}

/**
 * Turns attached photos (and any client-extracted document text) into plain
 * text through the existing vision pipeline, so the chat model itself never
 * needs to be multimodal.
 */
export async function extractChatAttachment(
  input: { images?: string[]; text?: string },
  options: { signal?: AbortSignal } = {},
): Promise<string> {
  // Attachment transcription follows the study-generation provider, if set.
  const generation = providersStore.getSnapshot().generation;
  let response: Response;
  try {
    response = await fetch("/api/chat/extract", {
      method: "POST",
      headers: { "Content-Type": "application/json", ...authHeaders(), ...providerHeaders(generation?.provider), ...localeHeader() },
      body: JSON.stringify(generation ? { ...input, model: generation.visionModel || generation.textModel } : input),
      signal: options.signal,
    });
  } catch (error) {
    if (error instanceof Error && error.name === "AbortError") {
      throw new ApiError(t("api.cancelled"), "aborted");
    }
    throw new ApiError(t("api.unreachable"), "network");
  }
  const body = (await response.json().catch(() => null)) as { text?: string; error?: string; kind?: string } | null;
  if (!response.ok) {
    throw new ApiError(body?.error ?? t("api.httpError", { status: response.status }), body?.kind);
  }
  if (!body?.text?.trim()) throw new ApiError(t("chat.attachEmpty"), "bad_response");
  return body.text.trim();
}