import type {
  ChatMessage,
  Citation,
  Conversation,
  LegalDocument,
  LocalModelStatus,
  ModelPullHandlers,
  StreamHandlers,
} from "@/lib/types";

export const API_BASE = (process.env.NEXT_PUBLIC_API_BASE_URL || "http://localhost:8001/api").replace(
  /\/$/,
  "",
);

function apiUrl(path: string) {
  const href = `${API_BASE}${path}`;
  if (/^https?:\/\//i.test(href)) return href;
  if (typeof window === "undefined") return href;
  return new URL(href, window.location.origin).toString();
}

function apiUrlObject(path: string) {
  const href = `${API_BASE}${path}`;
  const base = typeof window === "undefined" ? "http://localhost" : window.location.origin;
  return new URL(href, base);
}

export function supportsLocalModelSetupClient() {
  return /^https?:\/\/(?:localhost|127\.0\.0\.1|\[::1\])/i.test(API_BASE);
}

async function readJson<T>(response: Response): Promise<T> {
  if (!response.ok) {
    const text = await response.text();
    let apiMessage: string | undefined;
    try {
      const payload = JSON.parse(text) as { detail?: string };
      apiMessage = payload.detail;
    } catch {
      apiMessage = undefined;
    }
    throw new Error(apiMessage || text || response.statusText);
  }
  return response.json() as Promise<T>;
}

export async function listDocuments(search?: string) {
  const url = apiUrlObject("/documents");
  if (search) url.searchParams.set("search", search);
  return readJson<LegalDocument[]>(await fetch(url));
}

export async function uploadDocument(file: File) {
  const form = new FormData();
  form.append("file", file);
  return readJson<LegalDocument & { chunk_count: number; duplicate: boolean }>(
    await fetch(apiUrl("/documents/upload"), {
      method: "POST",
      body: form,
    }),
  );
}

export async function listConversations() {
  return readJson<Conversation[]>(await fetch(apiUrl("/conversations")));
}

export async function listMessages(conversationId: string) {
  return readJson<ChatMessage[]>(await fetch(apiUrl(`/conversations/${conversationId}/messages`)));
}

export async function getLocalModelStatus(model = "qwen3:1.7b") {
  const url = apiUrlObject("/model/status");
  url.searchParams.set("model", model);
  return readJson<LocalModelStatus>(await fetch(url));
}

export async function enableLocalModel(model = "qwen3:1.7b") {
  return readJson<LocalModelStatus>(
    await fetch(apiUrl("/model/enable-local"), {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ model }),
    }),
  );
}

export function documentFileUrl(documentId: string) {
  return apiUrl(`/documents/${documentId}/file`);
}

export async function streamChat(
  request: { message: string; conversation_id?: string | null; top_k?: number },
  handlers: StreamHandlers,
) {
  const response = await fetch(apiUrl("/chat"), {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(request),
  });

  if (!response.ok || !response.body) {
    throw new Error((await response.text()) || "Unable to start chat stream.");
  }

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

  const handlePayload = (line: string) => {
    if (!line.startsWith("data:")) return;
    const raw = line.slice(5).trim();
    if (!raw) return;
    const event = JSON.parse(raw) as {
      type: string;
      conversation?: Conversation;
      label?: string;
      citations?: Citation[];
      delta?: string;
      conversation_id?: string;
      error?: string;
    };
    if (event.type === "conversation" && event.conversation) handlers.onConversation?.(event.conversation);
    if (event.type === "stage" && event.label) handlers.onStage?.(event.label);
    if (event.type === "citations" && event.citations) handlers.onCitations?.(event.citations);
    if (event.type === "answer_delta" && event.delta) handlers.onDelta?.(event.delta);
    if (event.type === "done" && event.conversation_id) handlers.onDone?.(event.conversation_id);
    if (event.type === "error" && event.error) handlers.onError?.(event.error);
  };

  while (true) {
    const { value, done } = await reader.read();
    if (done) break;
    buffer += decoder.decode(value, { stream: true });
    const events = buffer.split("\n\n");
    buffer = events.pop() || "";
    for (const event of events) {
      for (const line of event.split("\n")) {
        handlePayload(line);
      }
    }
  }

  if (buffer.trim()) {
    for (const line of buffer.split("\n")) {
      handlePayload(line);
    }
  }
}

export async function streamLocalModelPull(model: string, handlers: ModelPullHandlers) {
  const response = await fetch(apiUrl("/model/pull"), {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ model }),
  });

  if (!response.ok || !response.body) {
    throw new Error((await response.text()) || "Unable to start model download.");
  }

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

  const handlePayload = (line: string) => {
    if (!line.startsWith("data:")) return;
    const raw = line.slice(5).trim();
    if (!raw) return;
    const event = JSON.parse(raw) as {
      type: string;
      status?: string;
      completed?: number | null;
      total?: number | null;
      model?: string;
      error?: string;
    };
    if (event.type === "progress" && event.status) {
      handlers.onProgress?.({
        status: event.status,
        completed: event.completed,
        total: event.total,
      });
    }
    if (event.type === "done" && event.model) handlers.onDone?.(event.model);
    if (event.type === "error" && event.error) handlers.onError?.(event.error);
  };

  while (true) {
    const { value, done } = await reader.read();
    if (done) break;
    buffer += decoder.decode(value, { stream: true });
    const events = buffer.split("\n\n");
    buffer = events.pop() || "";
    for (const event of events) {
      for (const line of event.split("\n")) {
        handlePayload(line);
      }
    }
  }

  if (buffer.trim()) {
    for (const line of buffer.split("\n")) {
      handlePayload(line);
    }
  }
}