import { NextRequest } from "next/server";
import { promises as fs } from "fs";
import os from "os";
import path from "path";

export const runtime = "nodejs";

const BASE_URL = process.env.BASE_URL || "https://llama.gptbox.dev/v1";
const API_KEY = process.env.OPENAI_API_KEY || "";
const MODEL_ID = process.env.MODEL_ID || "qwen3-4b-thinking-2507-claude-4.5-opus-distill";

const SEARXNG_CONFIG = {
    command: "npx",
    args: ["-y", "@kevinwatt/mcp-server-searxng"],
    env: {
        SEARXNG_INSTANCES: "https://searxng.gptbox.dev",
        SEARXNG_USER_AGENT: "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36",
        NODE_TLS_REJECT_UNAUTHORIZED: "0",
    },
};

const WEB_SEARCH_TOOL = {
    type: "function" as const,
    function: {
        name: "web_search",
        description: "Search the web for current information. Use this when you need up-to-date information.",
        parameters: {
            type: "object",
            properties: {
                query: { type: "string", description: "Search query" },
            },
            required: ["query"],
        },
    },
};

async function executeWebSearch(query: string): Promise<string> {
    try {
        const { Client } = await import("@modelcontextprotocol/sdk/client/index.js");
        const { StdioClientTransport } = await import("@modelcontextprotocol/sdk/client/stdio.js");

        const transport = new StdioClientTransport({
            command: SEARXNG_CONFIG.command,
            args: SEARXNG_CONFIG.args,
            env: { ...process.env, ...SEARXNG_CONFIG.env },
        });

        const client = new Client({ name: "chat-client", version: "1.0.0" });
        await client.connect(transport);

        const result = await client.callTool({
            name: "web_search",
            arguments: { query },
        });

        await client.close();

        if (result.content && Array.isArray(result.content)) {
            return result.content
                .map((c: { type: string; text?: string }) => (c.type === "text" ? c.text : ""))
                .filter(Boolean)
                .join("\n");
        }
        return "No results found.";
    } catch (error) {
        console.error("Web search error:", error);
        return `Search error: ${error instanceof Error ? error.message : "Unknown error"}`;
    }
}

const storageDirPromise = (async () => {
    const candidates: Array<string | undefined> = [
        process.env.DATA_DIR,
        process.env.HF_HOME,
        process.env.HOME,
        "/tmp",
        os.tmpdir(),
        process.cwd(),
    ];

    const seen = new Set<string>();
    const unique = candidates.filter((c): c is string => {
        if (!c) return false;
        if (seen.has(c)) return false;
        seen.add(c);
        return true;
    });

    for (const dir of unique) {
        try {
            await fs.mkdir(dir, { recursive: true });
            const probe = path.join(dir, ".write-probe");
            await fs.writeFile(probe, "ok", "utf8");
            await fs.unlink(probe);
            return dir;
        } catch {
            // try next
        }
    }

    return os.tmpdir();
})();

async function getLogFilePath() {
    if (process.env.CHAT_LOG_PATH) return process.env.CHAT_LOG_PATH;
    const baseDir = await storageDirPromise;
    return path.join(baseDir, "chat-logs.jsonl");
}

async function getUsageFilePath() {
    if (process.env.USAGE_STATS_PATH) return process.env.USAGE_STATS_PATH;
    const baseDir = await storageDirPromise;
    return path.join(baseDir, "usage-stats.json");
}

type UsageStats = {
    totalRequests: number;
    perDay: Record<string, number>;
    lastUpdated: string;
};

async function readUsageStats(): Promise<UsageStats> {
    try {
        const usageFile = await getUsageFilePath();
        const raw = await fs.readFile(usageFile, "utf8");
        const parsed = JSON.parse(raw) as Partial<UsageStats>;
        return {
            totalRequests: typeof parsed.totalRequests === "number" ? parsed.totalRequests : 0,
            perDay: parsed.perDay && typeof parsed.perDay === "object" ? (parsed.perDay as Record<string, number>) : {},
            lastUpdated: typeof parsed.lastUpdated === "string" ? parsed.lastUpdated : new Date(0).toISOString(),
        };
    } catch {
        return {
            totalRequests: 0,
            perDay: {},
            lastUpdated: new Date(0).toISOString(),
        };
    }
}

async function writeUsageStats(stats: UsageStats) {
    const payload: UsageStats = {
        totalRequests: stats.totalRequests,
        perDay: stats.perDay,
        lastUpdated: stats.lastUpdated,
    };
    try {
        const usageFile = await getUsageFilePath();
        await fs.mkdir(path.dirname(usageFile), { recursive: true });
        await fs.writeFile(usageFile, JSON.stringify(payload, null, 2), "utf8");
    } catch (error) {
        // Don't fail chat if stats persistence isn't writable
        console.error("Failed to write usage stats:", error);
    }
}

async function incrementUsageStats() {
    try {
        const stats = await readUsageStats();
        const nowIso = new Date().toISOString();
        const day = nowIso.slice(0, 10);
        stats.totalRequests += 1;
        stats.perDay[day] = (stats.perDay[day] || 0) + 1;
        stats.lastUpdated = nowIso;
        await writeUsageStats(stats);
    } catch (error) {
        console.error("Failed to increment usage stats:", error);
    }
}

async function appendChatLog(entry: unknown) {
    try {
        const logFile = await getLogFilePath();
        const line = JSON.stringify(entry) + "\n";
        await fs.mkdir(path.dirname(logFile), { recursive: true });
        await fs.appendFile(logFile, line, "utf8");
    } catch (error) {
        // Don't fail chat if logging isn't writable
        console.error("Failed to write chat log:", error);
        // Fallback to OS temp directory (best effort)
        try {
            const fallback = path.join(os.tmpdir(), "chat-logs.jsonl");
            await fs.appendFile(fallback, JSON.stringify(entry) + "\n", "utf8");
        } catch {
            // ignore
        }
    }
}

// Helper to stream a single completion request
async function streamCompletion(
    currentMessages: Array<{ role: string; content: string | null; tool_calls?: unknown; tool_call_id?: string }>,
    tools: typeof WEB_SEARCH_TOOL[] | undefined,
    send: (data: object) => void,
    abortSignal?: AbortSignal
): Promise<{
    content: string;
    reasoning: string;
    toolCalls: Array<{ id: string; function: { name: string; arguments: string } }>;
}> {
    const response = await fetch(`${BASE_URL}/chat/completions`, {
        method: "POST",
        headers: {
            "Content-Type": "application/json",
            Authorization: `Bearer ${API_KEY}`,
        },
        body: JSON.stringify({
            model: MODEL_ID,
            messages: currentMessages,
            tools,
            tool_choice: tools ? "auto" : undefined,
            stream: true,
            max_tokens: 4096,
        }),
    });

    if (!response.ok) {
        throw new Error(`API error: ${response.status}`);
    }

    const reader = response.body?.getReader();
    if (!reader) throw new Error("No reader");

    const decoder = new TextDecoder();
    let buffer = "";
    let content = "";
    let reasoning = "";
    const toolCalls: Array<{ id: string; function: { name: string; arguments: string } }> = [];
    let currentToolCall: { id: string; function: { name: string; arguments: string } } | null = null;

    while (true) {
        if (abortSignal?.aborted) {
            try {
                await reader.cancel();
            } catch {
                // ignore cancel errors
            }
            break;
        }
        const { done, value } = await reader.read();
        if (done) break;

        buffer += decoder.decode(value, { stream: true });
        const lines = buffer.split("\n");
        buffer = lines.pop() || "";

        for (const line of lines) {
            if (!line.startsWith("data: ")) continue;
            const data = line.slice(6).trim();
            if (data === "[DONE]") continue;

            try {
                const parsed = JSON.parse(data);
                const delta = parsed.choices?.[0]?.delta;

                // Handle reasoning content (vLLM uses delta.reasoning, DeepSeek uses delta.reasoning_content)
                const reasoningChunk = delta?.reasoning || delta?.reasoning_content;
                if (reasoningChunk) {
                    reasoning += reasoningChunk;
                    send({ type: "reasoning", content: reasoningChunk });
                }

                // Handle regular content
                if (delta?.content) {
                    content += delta.content;
                    send({ type: "content", content: delta.content });
                }

                // Handle tool calls
                if (delta?.tool_calls) {
                    for (const tc of delta.tool_calls) {
                        if (tc.id) {
                            currentToolCall = {
                                id: tc.id,
                                function: { name: tc.function?.name || "", arguments: "" },
                            };
                            toolCalls.push(currentToolCall);
                        }
                        if (tc.function?.name && currentToolCall) {
                            currentToolCall.function.name = tc.function.name;
                        }
                        if (tc.function?.arguments && currentToolCall) {
                            currentToolCall.function.arguments += tc.function.arguments;
                        }
                    }
                }
            } catch {
                // Ignore parse errors
            }
        }
    }

    return { content, reasoning, toolCalls };
}

export async function POST(req: NextRequest) {
    const { messages, searchEnabled } = await req.json();

    const encoder = new TextEncoder();
    const stream = new ReadableStream({
        async start(controller) {
            let closed = false;
            const safeEnqueue = (chunk: string) => {
                if (closed || req.signal.aborted) return;
                try {
                    controller.enqueue(encoder.encode(chunk));
                } catch {
                    closed = true;
                }
            };
            const send = (data: object) => {
                safeEnqueue(`data: ${JSON.stringify(data)}\n\n`);
            };

            // If the client disconnects, stop streaming gracefully
            req.signal.addEventListener("abort", () => {
                closed = true;
                try {
                    controller.close();
                } catch {
                    // already closed
                }
            });

            const timestamp = new Date().toISOString();
            const logRounds: Array<{
                content: string;
                reasoning: string;
                toolCalls: Array<{ id: string; name: string; args: string }>;
            }> = [];
            let logError: string | null = null;

            try {
                // Fire-and-forget so chat never fails due to stats IO
                void incrementUsageStats();
                const nowIso = new Date().toISOString();
                const today = nowIso.slice(0, 10);
                const currentYear = nowIso.slice(0, 4);
                const systemMessage = {
                    role: "system",
                    content: `You are a helpful AI assistant. The current date/time is ${nowIso} (UTC). The current year is ${currentYear}. If web search is enabled and the user asks for up-to-date information (e.g., the latest in, news, current events, recent updates), you MUST call the web_search tool.`,
                };

                const tools = searchEnabled ? [WEB_SEARCH_TOOL] : undefined;
                let currentMessages: Array<{ role: string; content: string | null; tool_calls?: unknown; tool_call_id?: string }> = [
                    systemMessage,
                    ...messages,
                ];

                // Loop for tool calls - model reasons, calls tool, then we send results back
                for (let round = 0; round < 5; round++) {
                    const { content, reasoning, toolCalls } = await streamCompletion(
                        currentMessages,
                        tools,
                        send,
                        req.signal as unknown as AbortSignal
                    );

                    logRounds.push({
                        content,
                        reasoning,
                        toolCalls: toolCalls.map((tc) => ({
                            id: tc.id,
                            name: tc.function.name,
                            args: tc.function.arguments,
                        })),
                    });

                    // If no tool calls, we're done
                    if (toolCalls.length === 0) {
                        break;
                    }

                    // Add assistant message with tool calls to history
                    currentMessages.push({
                        role: "assistant",
                        content: content || null,
                        tool_calls: toolCalls.map((tc) => ({
                            id: tc.id,
                            type: "function",
                            function: tc.function,
                        })),
                    });

                    // Execute tool calls and add results to history
                    for (const tc of toolCalls) {
                        const args = JSON.parse(tc.function.arguments || "{}");
                        send({
                            type: "tool_call",
                            name: tc.function.name,
                            args,
                            status: "running",
                        });

                        let result = "";
                        if (tc.function.name === "web_search") {
                            result = await executeWebSearch(args.query);
                        }

                        send({
                            type: "tool_call",
                            name: tc.function.name,
                            args,
                            status: "complete",
                            result: result.slice(0, 2000),
                        });

                        // Add tool result to messages for next round
                        currentMessages.push({
                            role: "tool",
                            tool_call_id: tc.id,
                            content: result,
                        });
                    }

                    // Signal new reasoning block for next round
                    send({ type: "reasoning_start" });

                    // Continue loop to get model's response with tool results
                }

                send({ type: "done" });
            } catch (error) {
                console.error("Chat error:", error);
                logError = error instanceof Error ? error.message : String(error);
                send({
                    type: "error",
                    message: error instanceof Error ? error.message : "Unknown error",
                });
            } finally {
                // Fire-and-forget logging of raw chat history for debugging
                void appendChatLog({
                    timestamp,
                    searchEnabled,
                    messages,
                    rounds: logRounds,
                    error: logError,
                });
                safeEnqueue("data: [DONE]\n\n");
                if (!closed) {
                    try {
                        controller.close();
                        closed = true;
                    } catch {
                        // ignore
                    }
                }
            }
        },
    });

    return new Response(stream, {
        headers: {
            "Content-Type": "text/event-stream",
            "Cache-Control": "no-cache",
            Connection: "keep-alive",
        },
    });
}

// Optional: expose logs for download via API
export async function GET(req: NextRequest) {
    const url = new URL(req.url);
    const wantLogs = url.searchParams.get("logs");
    if (wantLogs) {
        try {
            const logFile = await getLogFilePath();
            const limitParam = url.searchParams.get("limit");
            const limit = Math.max(1, Math.min(5000, parseInt(limitParam || "1000", 10)));
            const raw = await fs.readFile(logFile, "utf8").catch(() => "");
            if (!raw) {
                return new Response(JSON.stringify({ error: "No logs found" }), {
                    status: 404,
                    headers: { "Content-Type": "application/json" },
                });
            }
            const lines = raw.split(/\r?\n/).filter(Boolean);
            const slice = lines.slice(-limit).join("\n") + "\n";
            return new Response(slice, {
                headers: {
                    "Content-Type": "text/plain; charset=utf-8",
                    "Cache-Control": "no-cache",
                },
            });
        } catch (error) {
            return new Response(
                JSON.stringify({ error: error instanceof Error ? error.message : String(error) }),
                { status: 500, headers: { "Content-Type": "application/json" } }
            );
        }
    }
    return new Response(JSON.stringify({ ok: true }), {
        headers: { "Content-Type": "application/json" },
    });
}