frontend/src/lib/api.ts

import type { Message, QueryResult } from "../types";

const BASE_URL = "";

/**
 * POST /api/auth/login
 *
 * Sends the shared password to the API and returns a signed JWT on success.
 * Throws an error with message "Invalid password" on HTTP 401.
 * Throws a generic error for any other non-200 response.
 */
export async function login(password: string): Promise<{ token: string }> {
  const response = await fetch(`${BASE_URL}/api/auth/login`, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ password }),
  });

  if (response.status === 401) {
    throw new Error("Invalid password");
  }

  if (!response.ok) {
    throw new Error(`Login failed: ${response.status} ${response.statusText}`);
  }

  return response.json() as Promise<{ token: string }>;
}

/**
 * POST /api/query/stream
 *
 * Opens a streaming SSE connection to the query endpoint and dispatches
 * events to the provided callbacks:
 *   - onToken(text)  — called for each `token` SSE event
 *   - onDone(meta)   — called once when the `done` SSE event is received
 *   - onError(msg)   — called if an `error` SSE event is received
 *
 * Uses fetch + ReadableStream so the JWT can be sent in the Authorization
 * header (EventSource does not support custom headers).
 */
export async function streamQuery(
  payload: {
    query: string;
    history: Message[];
    profession: string | null;
    language: string | null;
  },
  token: string,
  signal: AbortSignal,
  onToken: (text: string) => void,
  onDone: (metadata: QueryResult) => void,
  onError: (message: string) => void
): Promise<void> {
  const response = await fetch(`${BASE_URL}/api/query/stream`, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${token}`,
    },
    body: JSON.stringify(payload),
    signal,
  });

  if (response.status === 401) {
    // Throw a recognisable message so useStream can skip retries and
    // App.tsx can call handle401() to clear the token and show the gate.
    throw new Error("Unauthorized");
  }

  if (!response.ok) {
    throw new Error(
      `Stream request failed: ${response.status} ${response.statusText}`
    );
  }

  if (!response.body) {
    throw new Error("Response body is null — streaming not supported");
  }

  const reader = response.body.getReader();
  const decoder = new TextDecoder("utf-8");

  // Buffer for incomplete lines that span chunk boundaries
  let lineBuffer = "";
  // The most recently seen `event:` line value
  let currentEvent = "";

  try {
    while (true) {
      const { done, value } = await reader.read();
      if (done) break;

      lineBuffer += decoder.decode(value, { stream: true });

      // Process all complete lines (terminated by \n)
      const lines = lineBuffer.split("\n");
      // Keep the last (potentially incomplete) segment in the buffer
      lineBuffer = lines.pop() ?? "";

      for (const rawLine of lines) {
        const line = rawLine.trimEnd(); // strip trailing \r if present

        if (line === "") {
          // Blank line = end of SSE message; reset event type
          currentEvent = "";
          continue;
        }

        if (line.startsWith("event:")) {
          currentEvent = line.slice("event:".length).trim();
          continue;
        }

        if (line.startsWith("data:")) {
          const jsonStr = line.slice("data:".length).trim();

          try {
            const parsed = JSON.parse(jsonStr) as Record<string, unknown>;

            switch (currentEvent) {
              case "token": {
                const text = parsed["text"];
                if (typeof text === "string") {
                  onToken(text);
                }
                break;
              }
              case "done": {
                onDone(parsed as unknown as QueryResult);
                break;
              }
              case "error": {
                const message = parsed["message"];
                onError(typeof message === "string" ? message : jsonStr);
                return; // Close immediately on error event
              }
              default:
                // Unknown event type — ignore
                break;
            }
          } catch {
            // Malformed JSON in data line — skip silently
          }
        }
      }
    }
  } finally {
    reader.releaseLock();
  }
}