/**
 * Custom LangChain ChatModel for Cloudflare Workers AI
 *
 * Cloudflare Workers AI has limitations:
 * - Does NOT support multi-turn tool conversations (error 3043)
 * - Some models (Mistral) output tools as text: [TOOL_CALLS][{...}]
 *
 * This class handles these quirks to provide a LangChain-compatible interface.
 */

import { BaseChatModel } from "@langchain/core/language_models/chat_models";
import { AIMessage } from "@langchain/core/messages";
import { getCloudflareAccountId, getCloudflareApiToken } from "./providerConfig.js";
import { toolSchemas } from "./langchainTools.js";
import { zodToJsonSchema } from "zod-to-json-schema";

/**
 * Try to repair and parse a potentially truncated JSON object
 */
function tryRepairAndParse(jsonStr) {
    try {
        return JSON.parse(jsonStr);
    } catch (e) {
        const repairs = [
            jsonStr + '}',
            jsonStr + '"}',
            jsonStr + '}}',
            jsonStr + '"}}',
            jsonStr + ': null}}',
            jsonStr + '": null}}'
        ];

        for (const attempt of repairs) {
            try {
                const parsed = JSON.parse(attempt);
                if (parsed.name) {
                    return parsed;
                }
            } catch (e2) {
                // Continue trying
            }
        }
        return null;
    }
}

/**
 * Parse tool calls from text response
 * Handles: [TOOL_CALLS][{...}] and [Called tool: name({args})]
 */
function parseTextToolCalls(text) {
    if (!text) return { cleanText: '', toolCalls: [] };

    const toolCalls = [];
    let cleanText = text;

    // Format 1: [TOOL_CALLS][...] (Mistral native format)
    const toolCallMatch = text.match(/\[TOOL_CALLS\]\s*(\[[\s\S]*)/);

    if (toolCallMatch) {
        const toolCallsJson = toolCallMatch[1];

        // Try normal JSON.parse first
        try {
            const parsedCalls = JSON.parse(toolCallsJson);
            if (Array.isArray(parsedCalls)) {
                const validCalls = parsedCalls
                    .filter(call => call && call.name)
                    .map(call => ({
                        id: `toolu_cf_${Date.now()}_${toolCalls.length}`,
                        name: call.name,
                        args: call.arguments || {}
                    }));

                cleanText = text.replace(/\[TOOL_CALLS\]\s*\[[\s\S]*/, '').trim();
                return { cleanText, toolCalls: validCalls };
            }
        } catch (e) {
            // Try multi-line format
        }

        // Try parsing as multiple single-element arrays on separate lines
        const lines = toolCallsJson.split('\n');
        const lineMatches = [];

        for (const line of lines) {
            const trimmed = line.trim();
            if (trimmed.startsWith('[') && trimmed.endsWith(']')) {
                try {
                    const parsed = JSON.parse(trimmed);
                    if (Array.isArray(parsed) && parsed.length > 0 && parsed[0].name) {
                        lineMatches.push({
                            id: `toolu_cf_${Date.now()}_${lineMatches.length}`,
                            name: parsed[0].name,
                            args: parsed[0].arguments || {}
                        });
                    }
                } catch (e) {
                    const objMatch = trimmed.match(/\[\s*(\{[\s\S]*)/);
                    if (objMatch) {
                        const repaired = tryRepairAndParse(objMatch[1].replace(/\]\s*$/, ''));
                        if (repaired && repaired.name) {
                            lineMatches.push({
                                id: `toolu_cf_${Date.now()}_${lineMatches.length}`,
                                name: repaired.name,
                                args: repaired.arguments || {}
                            });
                        }
                    }
                }
            }
        }

        if (lineMatches.length > 0) {
            cleanText = text.replace(/\[TOOL_CALLS\][\s\S]*/, '').trim();
            return { cleanText, toolCalls: lineMatches };
        }

        // Extract individual tool calls using regex for truncated JSON
        const startPattern = /\{"name"\s*:\s*"/g;
        let match;
        const toolCallStarts = [];

        while ((match = startPattern.exec(toolCallsJson)) !== null) {
            toolCallStarts.push(match.index);
        }

        for (let i = 0; i < toolCallStarts.length; i++) {
            const start = toolCallStarts[i];
            const end = toolCallStarts[i + 1] || toolCallsJson.length;
            let segment = toolCallsJson.substring(start, end).replace(/,\s*$/, '');
            const parsed = tryRepairAndParse(segment);

            if (parsed && parsed.name) {
                toolCalls.push({
                    id: `toolu_cf_${Date.now()}_${i}`,
                    name: parsed.name,
                    args: parsed.arguments || {}
                });
            }
        }

        cleanText = text.replace(/\[TOOL_CALLS\]\s*\[[\s\S]*/, '').trim();
        if (toolCalls.length > 0) {
            return { cleanText, toolCalls };
        }
    }

    // Format 2: [Called tool: name({args})]
    const calledToolPattern = /\[Called tool:\s*(\w+)\((\{[\s\S]*?\})\)\]/g;
    let calledMatch;

    while ((calledMatch = calledToolPattern.exec(text)) !== null) {
        try {
            const args = JSON.parse(calledMatch[2]);
            toolCalls.push({
                id: `toolu_cf_${Date.now()}_${toolCalls.length}`,
                name: calledMatch[1],
                args: args
            });
            cleanText = cleanText.replace(calledMatch[0], '');
        } catch (e) {
            const repaired = tryRepairAndParse(calledMatch[2]);
            if (repaired) {
                toolCalls.push({
                    id: `toolu_cf_${Date.now()}_${toolCalls.length}`,
                    name: calledMatch[1],
                    args: repaired
                });
                cleanText = cleanText.replace(calledMatch[0], '');
            }
        }
    }

    return { cleanText: cleanText.trim(), toolCalls };
}

/**
 * Convert LangChain messages to Cloudflare format
 * IMPORTANT: Converts tool history to text (Cloudflare limitation)
 */
function messagesToCloudflare(messages) {
    const cfMessages = [];

    for (const msg of messages) {
        const msgType = msg.constructor.name;

        if (msgType === 'SystemMessage') {
            cfMessages.push({
                role: "system",
                content: msg.content
            });
        } else if (msgType === 'HumanMessage') {
            cfMessages.push({
                role: "user",
                content: msg.content
            });
        } else if (msgType === 'AIMessage') {
            // Convert tool calls to text for Cloudflare
            let content = msg.content || '';
            if (msg.tool_calls && msg.tool_calls.length > 0) {
                const toolText = msg.tool_calls.map(tc =>
                    `[Called tool: ${tc.name}(${JSON.stringify(tc.args)})]`
                ).join('\n');
                content = content ? `${content}\n${toolText}` : toolText;
            }
            if (content) {
                cfMessages.push({
                    role: "assistant",
                    content: content
                });
            }
        } else if (msgType === 'ToolMessage') {
            // Convert tool results to user messages
            cfMessages.push({
                role: "user",
                content: `[Tool Result (${msg.name}): ${msg.content}]`
            });
        }
    }

    return cfMessages;
}

/**
 * ChatCloudflare - LangChain ChatModel for Cloudflare Workers AI
 */
export class ChatCloudflare extends BaseChatModel {
    static lc_name() {
        return "ChatCloudflare";
    }

    constructor(fields = {}) {
        super(fields);
        this.model = fields.model || "@cf/mistral/mistral-7b-instruct-v0.2";
        this.accountId = fields.accountId || getCloudflareAccountId();
        this.apiToken = fields.apiToken || getCloudflareApiToken();
        this.maxTokens = fields.maxTokens || 1024;
        this._tools = [];
    }

    _llmType() {
        return "cloudflare";
    }

    /**
     * Bind tools to this model instance
     */
    bindTools(tools) {
        const bound = new ChatCloudflare({
            model: this.model,
            accountId: this.accountId,
            apiToken: this.apiToken,
            maxTokens: this.maxTokens
        });

        // Convert tools to OpenAI format
        bound._tools = tools.map(tool => ({
            type: "function",
            function: {
                name: tool.name,
                description: tool.description,
                parameters: zodToJsonSchema(tool.schema, { target: "openApi3" })
            }
        }));

        return bound;
    }

    async _generate(messages, options, runManager) {
        const cfMessages = messagesToCloudflare(messages);

        const requestBody = {
            messages: cfMessages,
            max_tokens: this.maxTokens
        };

        // Add tools if bound
        if (this._tools.length > 0) {
            requestBody.tools = this._tools;
        }

        const endpoint = `https://api.cloudflare.com/client/v4/accounts/${this.accountId}/ai/run/${this.model}`;

        console.log(`[ChatCloudflare] Sending request to: ${endpoint}`);
        console.log(`[ChatCloudflare] Messages: ${cfMessages.length}, Tools: ${this._tools.length}`);

        const response = await fetch(endpoint, {
            method: "POST",
            headers: {
                "Content-Type": "application/json",
                "Authorization": `Bearer ${this.apiToken}`,
            },
            body: JSON.stringify(requestBody),
        });

        const cfData = await response.json();

        if (!cfData.success) {
            throw new Error(cfData.errors?.[0]?.message || "Cloudflare API error");
        }

        const result = cfData.result || cfData;

        // Get tool calls from proper field or parse from text
        let toolCalls = result.tool_calls || [];
        let textResponse = result.response || '';

        // Parse tool calls from text if not present natively
        if (toolCalls.length === 0 && textResponse) {
            const parsed = parseTextToolCalls(textResponse);
            if (parsed.toolCalls.length > 0) {
                toolCalls = parsed.toolCalls;
                textResponse = parsed.cleanText;
            }
        } else {
            // Convert native tool calls to LangChain format
            toolCalls = toolCalls.map((tc, i) => ({
                id: `toolu_cf_${Date.now()}_${i}`,
                name: tc.name,
                args: typeof tc.arguments === 'string' ? JSON.parse(tc.arguments) : (tc.arguments || {})
            }));
        }

        // Create AIMessage with tool calls
        const aiMessage = new AIMessage({
            content: textResponse,
            tool_calls: toolCalls.length > 0 ? toolCalls : undefined,
            usage_metadata: {
                input_tokens: result.usage?.prompt_tokens || 0,
                output_tokens: result.usage?.completion_tokens || 0
            }
        });

        return {
            generations: [{
                text: textResponse,
                message: aiMessage,
            }],
            llmOutput: {
                tokenUsage: {
                    promptTokens: result.usage?.prompt_tokens || 0,
                    completionTokens: result.usage?.completion_tokens || 0,
                }
            }
        };
    }
}

/**
 * Get a Cloudflare model instance with tools bound
 * @param {string} modelId - The Cloudflare model name
 * @returns {ChatCloudflare} ChatCloudflare instance with tools
 */
export function getCloudflareModel(modelId) {
    const model = new ChatCloudflare({ model: modelId });

    const langchainTools = Object.values(toolSchemas).map(tool => ({
        name: tool.name,
        description: tool.description,
        schema: tool.schema
    }));

    return model.bindTools(langchainTools);
}

export default ChatCloudflare;