export type SearchHit = {
  doc_id: string;
  page_num: number;
  score: number;
  image_key: string;
  image_url?: string | null;
  width: number;
  height: number;
};

export type SearchResponse = {
  query: string;
  results: SearchHit[];
};

export type ChatResponse = {
  answer: string;
  model: string;
  citations: SearchHit[];
  usage?: Record<string, unknown> | null;
};

export type ExportRequest = {
  query: string;
  top_k: number;
  include_images: boolean;
  hybrid: boolean;
  format: "json" | "markdown";
  include_snippets?: boolean;
  max_snippet_chars?: number;
  answer?: string | null;
};

export type ChatStreamEvent =
  | { event: "citations"; data: { citations: SearchHit[] } }
  | { event: "delta"; data: { text: string } }
  | { event: "done"; data: { model?: string; usage?: Record<string, unknown> | null } }
  | { event: "error"; data: { message: string } }
  | { event: "message"; data: unknown };

const API_BASE =
  process.env.NEXT_PUBLIC_API_BASE?.replace(/\/$/, "") ||
  "/api";

const DEFAULT_TIMEOUT_MS = 30000;
const MAX_ERROR_CHARS = 600;

function resolvePath(path: string) {
  if (path.startsWith("http://") || path.startsWith("https://")) {
    return path;
  }
  if (!path.startsWith("/")) {
    return `${API_BASE}/${path}`;
  }
  return `${API_BASE}${path}`;
}

export function resolveImageUrl(imageUrl?: string | null): string | null {
  if (!imageUrl) return null;
  if (imageUrl.startsWith("/files/")) return imageUrl;
  return resolvePath(imageUrl);
}

async function postJson<T>(path: string, payload: unknown): Promise<T> {
  const res = await fetchWithTimeout(resolvePath(path), {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify(payload),
    cache: "no-store",
  });

  if (!res.ok) {
    const text = truncateError(await res.text());
    throw new Error(`Request failed: ${res.status} ${text}`);
  }

  return (await res.json()) as T;
}

export async function exportEvidence(params: ExportRequest): Promise<Blob> {
  const res = await fetchWithTimeout(resolvePath("/export"), {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify(params),
    cache: "no-store",
  }, DEFAULT_TIMEOUT_MS);

  if (!res.ok) {
    const text = truncateError(await res.text());
    throw new Error(`Export failed: ${res.status} ${text}`);
  }

  return await res.blob();
}

export async function runSearch(params: {
  query: string;
  top_k: number;
  include_images: boolean;
  hybrid: boolean;
}): Promise<SearchResponse> {
  const response = await postJson<SearchResponse>("/search", params);
  const results = Array.isArray(response.results)
    ? response.results
        .map(normalizeHit)
        .filter((item): item is SearchHit => item !== null)
    : [];
  return {
    query: typeof response.query === "string" ? response.query : params.query,
    results,
  };
}

export async function runChat(params: {
  query: string;
  top_k: number;
  include_images: boolean;
  hybrid: boolean;
}): Promise<ChatResponse> {
  const response = await postJson<ChatResponse>("/chat", params);
  const citations = Array.isArray(response.citations)
    ? response.citations
        .map(normalizeHit)
        .filter((item): item is SearchHit => item !== null)
    : [];
  return {
    answer: typeof response.answer === "string" ? response.answer : "",
    model: typeof response.model === "string" ? response.model : "",
    citations,
    usage: typeof response.usage === "object" ? response.usage : null,
  };
}

function parseEventBlock(block: string): { event: string; data: string } | null {
  const lines = block.split(/\r?\n/);
  let event = "message";
  let data = "";
  for (const line of lines) {
    if (!line) continue;
    if (line.startsWith(":") || line.startsWith("retry:") || line.startsWith("id:")) {
      continue;
    }
    if (line.startsWith("event:")) {
      event = line.replace("event:", "").trim();
      continue;
    }
    if (line.startsWith("data:")) {
      let chunk = line.slice(5);
      if (chunk.startsWith(" ")) {
        chunk = chunk.slice(1);
      }
      data += chunk;
    }
  }
  if (!data) return null;
  return { event, data };
}

export async function streamChat(
  params: {
    query: string;
    top_k: number;
    include_images: boolean;
    hybrid: boolean;
  },
  onEvent: (event: ChatStreamEvent) => void,
  signal?: AbortSignal
): Promise<void> {
  const res = await fetch(resolvePath("/chat/stream"), {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Accept: "text/event-stream",
    },
    body: JSON.stringify(params),
    cache: "no-store",
    signal,
  });

  if (!res.ok) {
    const text = truncateError(await res.text());
    throw new Error(`Stream failed: ${res.status} ${text}`);
  }

  if (!res.body) {
    throw new Error("Stream failed: response body is empty.");
  }

  const reader = res.body.getReader();
  const decoder = new TextDecoder();
  let buffer = "";

  while (true) {
    const { value, done } = await reader.read();
    if (done) break;
    buffer += decoder.decode(value, { stream: true });
    const blocks = buffer.split("\n\n");
    buffer = blocks.pop() ?? "";
    for (const block of blocks) {
      const parsed = parseEventBlock(block);
      if (!parsed) continue;
      try {
        const payload = JSON.parse(parsed.data);
        onEvent({ event: parsed.event as ChatStreamEvent["event"], data: payload } as ChatStreamEvent);
      } catch {
        onEvent({ event: parsed.event as ChatStreamEvent["event"], data: parsed.data } as ChatStreamEvent);
      }
    }
  }

  if (buffer.trim()) {
    const parsed = parseEventBlock(buffer);
    if (parsed) {
      try {
        const payload = JSON.parse(parsed.data);
        onEvent({ event: parsed.event as ChatStreamEvent["event"], data: payload } as ChatStreamEvent);
      } catch {
        onEvent({ event: parsed.event as ChatStreamEvent["event"], data: parsed.data } as ChatStreamEvent);
      }
    }
  }
}

function truncateError(text: string): string {
  if (!text) return "";
  if (text.length <= MAX_ERROR_CHARS) return text;
  return `${text.slice(0, MAX_ERROR_CHARS)}…`;
}

async function fetchWithTimeout(
  input: RequestInfo | URL,
  init: RequestInit,
  timeoutMs: number = DEFAULT_TIMEOUT_MS
): Promise<Response> {
  const controller = new AbortController();
  if (init.signal) {
    if (init.signal.aborted) {
      controller.abort();
    } else {
      init.signal.addEventListener("abort", () => controller.abort(), { once: true });
    }
  }
  const timeout = setTimeout(() => controller.abort(), timeoutMs);
  try {
    return await fetch(input, {
      ...init,
      signal: controller.signal,
    });
  } finally {
    clearTimeout(timeout);
  }
}

function normalizeHit(raw: SearchHit | null | undefined): SearchHit | null {
  if (!raw || typeof raw !== "object") return null;
  const docId = typeof raw.doc_id === "string" ? raw.doc_id : "";
  const imageKey = typeof raw.image_key === "string" ? raw.image_key : "";
  const pageNum = Number(raw.page_num);
  const score = Number(raw.score);
  const width = Number(raw.width);
  const height = Number(raw.height);
  if (!docId || !imageKey || !Number.isFinite(pageNum)) return null;
  return {
    doc_id: docId,
    page_num: Number.isFinite(pageNum) ? pageNum : 0,
    score: Number.isFinite(score) ? score : 0,
    image_key: imageKey,
    image_url: typeof raw.image_url === "string" ? raw.image_url : (imageKey ? `/files/${imageKey}` : null),
    width: Number.isFinite(width) ? width : 0,
    height: Number.isFinite(height) ? height : 0,
  };
}