import React, { useState, useRef, useEffect } from 'react';
import ReactMarkdown from 'react-markdown';
// @ts-ignore
import remarkGfm from 'remark-gfm';
import { Icons } from '../constants';
import { sendChatMessage } from '../services/geminiService';
import { ChatMessage, AIModel, AVAILABLE_MODELS } from '../types';
import CompactModelSelector from './CompactModelSelector';

interface ChatInterfaceProps {
    onNavigateToPage: (page: number) => void;
}

const ChatInterface: React.FC<ChatInterfaceProps> = ({ onNavigateToPage }) => {
    const [selectedModel, setSelectedModel] = useState<AIModel>(AVAILABLE_MODELS[0]);
    const [messages, setMessages] = useState<ChatMessage[]>([
        { role: 'model', content: "Hello! I've analyzed your document. Ask me anything about it." }
    ]);
    const [input, setInput] = useState('');
    const [loading, setLoading] = useState(false);
    const [useRLM, setUseRLM] = useState(false);
    const messagesEndRef = useRef<HTMLDivElement>(null);

    const scrollToBottom = () => {
        messagesEndRef.current?.scrollIntoView({ behavior: "smooth" });
    };

    useEffect(() => {
        scrollToBottom();
    }, [messages]);

    const handleSend = async () => {
        if (!input.trim() || loading) return;

        const userMsg: ChatMessage = { role: 'user', content: input };
        setMessages(prev => [...prev, userMsg]);
        setInput('');
        setLoading(true);

        try {
            // Build conversation history from previous messages (excluding the current one we just added)
            // Format: [{role: "user"|"assistant", content: "..."}]
            // Skip the initial greeting and only include actual conversation
            const conversationHistory = messages
                .filter((msg, idx) => idx > 0) // Skip initial AI greeting
                .map(msg => ({
                    role: msg.role === 'model' ? 'assistant' : 'user',
                    content: msg.content
                }));

            // For RLM mode, we can optionally skip history as deep research handles context differently
            // But for normal chat, always pass history
            const historyToSend = useRLM ? [] : conversationHistory;

            const response = await sendChatMessage(userMsg.content, historyToSend, selectedModel, useRLM);
            const botMsg: ChatMessage = {
                role: 'model',
                content: response.answer,
                reasoning_trace: response.reasoning_trace
            };
            setMessages(prev => [...prev, botMsg]);
        } catch (error) {
            setMessages(prev => [...prev, { role: 'model', content: "Sorry, I encountered an error answering that. Please try again." }]);
        } finally {
            setLoading(false);
        }
    };

    const handleKeyDown = (e: React.KeyboardEvent) => {
        if (e.key === 'Enter' && !e.shiftKey) {
            e.preventDefault();
            handleSend();
        }
    };

    return (
        <div className="flex flex-col h-full bg-gradient-to-b from-industrial-900/80 to-industrial-950/90 rounded-2xl border border-industrial-700/50 overflow-hidden backdrop-blur-sm shadow-2xl shadow-black/20">
            {/* Header with Model Selector */}
            <div className="px-3 py-2 border-b border-industrial-700/50 bg-industrial-900/60 backdrop-blur-md flex justify-between items-center shrink-0">
                <div className="flex items-center gap-2">
                    <div className="w-1.5 h-1.5 rounded-full bg-petro-500 animate-pulse shadow-lg shadow-petro-500/50"></div>
                    <span className="text-xs font-medium text-gray-300">AI Assistant</span>
                </div>
                <CompactModelSelector
                    selectedModel={selectedModel}
                    onModelChange={setSelectedModel}
                    disabled={loading}
                />
            </div>

            {/* Messages Area */}
            <div className="flex-1 overflow-y-auto p-4 space-y-4 custom-scrollbar min-h-0">
                {messages.map((msg, idx) => {
                    const isUser = msg.role === 'user';
                    // Convert page citations to clickable links
                    // Handle multiple formats: [Page X], [page X], (Page X), Page X, etc.
                    // Match [Page X], (Page X), Page X, p. X formats (case insensitive)
                    let markdownContent = msg.content
                        // Standardize [Page X] -> [Page X](citation:X)
                        .replace(/\[(?:page|p\.?)\s*(\d+)\]/gi, '[Page $1](citation:$1)')
                        // Standardize (Page X) -> [Page X](citation:X)
                        .replace(/\((?:page|p\.?)\s*(\d+)\)/gi, '[Page $1](citation:$1)')
                        // Standardize plain "Page X" if not already linked -> [Page X](citation:X)
                        // Negative lookbehind/ahead would be ideal but complex in JS regex for all cases, 
                        // so we use a simpler approach that avoids double-linking
                        .replace(/(?<!\[|\]|\()(?:\b(?:page|p\.?)\s+(\d+))\b(?![^\[]*\]|\))/gi, '[Page $1](citation:$1)')
                        // Cleanup any accidental double links or malformed ones
                        .replace(/\[Page (\d+)\]\([^)]*citation:\d+[^)]*\)/gi, '[Page $1](citation:$1)');

                    return (
                        <div
                            key={idx}
                            className={`flex ${isUser ? 'justify-end' : 'justify-start'} animate-fadeIn`}
                            style={{ animationDelay: `${idx * 50}ms` }}
                        >
                            <div
                                className={`max-w-[90%] p-3 rounded-2xl text-sm leading-relaxed transition-all duration-300 hover:shadow-lg ${isUser
                                    ? 'bg-gradient-to-br from-petro-600 to-petro-700 text-white rounded-br-md shadow-lg shadow-petro-900/30'
                                    : 'bg-industrial-800/80 backdrop-blur-sm text-gray-200 rounded-bl-md border border-industrial-700/50 hover:border-industrial-600/50'
                                    }`}
                            >
                                {isUser ? (
                                    <div className="whitespace-pre-wrap">{msg.content}</div>
                                ) : (
                                    <div className="flex gap-2 items-start">
                                        <div className="mt-1 min-w-[16px] shrink-0 text-petro-400">
                                            <div className="w-4 h-4 rounded-full bg-petro-600/20 flex items-center justify-center">
                                                <Icons.Cpu className="w-2.5 h-2.5" />
                                            </div>
                                        </div>
                                        <div className="w-full overflow-hidden">
                                            {msg.reasoning_trace && msg.reasoning_trace.length > 0 && (
                                                <div className="mb-2 rounded-lg bg-gradient-to-br from-industrial-900/80 to-industrial-950/60 border border-industrial-700/30 overflow-hidden backdrop-blur-sm">
                                                    <details className="group">
                                                        <summary className="flex items-center gap-2 p-2 bg-industrial-900/50 cursor-pointer text-[10px] font-medium text-gray-400 hover:text-gray-200 select-none transition-colors">
                                                            <Icons.Activity className="w-3 h-3 text-petro-500" />
                                                            <span>Deep Research ({msg.reasoning_trace.length} steps)</span>
                                                            <div className="ml-auto transform group-open:rotate-180 transition-transform duration-300">
                                                                <Icons.ChevronDown className="w-3 h-3" />
                                                            </div>
                                                        </summary>
                                                        <div className="p-2 space-y-2 bg-industrial-950/50 text-[10px] border-t border-industrial-700/30 max-h-[200px] overflow-y-auto custom-scrollbar">
                                                            {msg.reasoning_trace.map((step, sIdx) => (
                                                                <div key={sIdx} className="space-y-1 animate-fadeIn" style={{ animationDelay: `${sIdx * 50}ms` }}>
                                                                    <div className="flex items-center gap-1.5 text-gray-400">
                                                                        <span className="font-mono bg-petro-900/50 text-petro-400 px-1 py-0.5 rounded text-[9px] border border-petro-800/50">{step.step}</span>
                                                                        <span className="font-medium text-gray-300 truncate">{step.thought}</span>
                                                                    </div>
                                                                    {step.type === 'execute' && step.content && (
                                                                        <div className="ml-2 pl-2 border-l border-petro-800/50">
                                                                            <div className="bg-industrial-950/80 p-2 rounded border border-industrial-800/50 font-mono text-gray-500 overflow-x-auto">
                                                                                <pre className="text-[9px]">{step.content}</pre>
                                                                            </div>
                                                                        </div>
                                                                    )}
                                                                </div>
                                                            ))}
                                                        </div>
                                                    </details>
                                                </div>
                                            )}
                                            <div className="prose prose-invert prose-xs max-w-none">
                                                <ReactMarkdown
                                                    remarkPlugins={[remarkGfm]}
                                                    components={{
                                                        a: ({ node: _node, href, children, ...props }) => {
                                                            // Check for citation: prefix
                                                            if (href?.startsWith('citation:')) {
                                                                const pageNum = parseInt(href.replace('citation:', ''), 10);
                                                                return (
                                                                    <button
                                                                        onClick={() => onNavigateToPage(pageNum)}
                                                                        className="text-petro-400 hover:text-petro-300 underline underline-offset-2 transition-colors duration-200 font-medium cursor-pointer"
                                                                    >
                                                                        {children}
                                                                    </button>
                                                                );
                                                            }
                                                            // Also catch any remaining page links that slip through
                                                            const childText = String(children);
                                                            const pageMatch = childText.match(/page\s*(\d+)/i);
                                                            if (pageMatch) {
                                                                const pageNum = parseInt(pageMatch[1], 10);
                                                                return (
                                                                    <button
                                                                        onClick={() => onNavigateToPage(pageNum)}
                                                                        className="text-petro-400 hover:text-petro-300 underline underline-offset-2 transition-colors duration-200 font-medium cursor-pointer"
                                                                    >
                                                                        {children}
                                                                    </button>
                                                                );
                                                            }
                                                            return <a href={href} {...props} target="_blank" rel="noopener noreferrer" className="text-petro-400 hover:text-petro-300 transition-colors">{children}</a>;
                                                        },
                                                        table: ({ node: _node, ...props }) => (
                                                            <div className="overflow-x-auto my-2 rounded border border-industrial-700/50">
                                                                <table {...props} className="min-w-full text-xs border-collapse" />
                                                            </div>
                                                        ),
                                                        thead: ({ node: _node, ...props }) => <thead {...props} className="bg-industrial-800/80" />,
                                                        th: ({ node: _node, ...props }) => <th {...props} className="border border-industrial-700/50 px-2 py-1.5 text-left font-semibold text-gray-300" />,
                                                        td: ({ node: _node, ...props }) => <td {...props} className="border border-industrial-700/50 px-2 py-1.5 text-gray-400" />,
                                                        code: ({ node: _node, className, children, ...props }: any) => {
                                                            const match = /language-(\w+)/.exec(className || '');
                                                            return match ? (
                                                                <code {...props} className="block bg-industrial-950/80 p-2 rounded text-xs font-mono my-2 overflow-x-auto border border-industrial-700/50" />
                                                            ) : (
                                                                <code {...props} className="bg-petro-900/30 px-1 py-0.5 rounded text-xs font-mono text-petro-300 border border-petro-800/30" />
                                                            );
                                                        },
                                                        p: ({ node: _node, ...props }) => (
                                                            <p {...props} className="mb-2 last:mb-0 leading-relaxed" />
                                                        ),
                                                    }}
                                                >
                                                    {markdownContent}
                                                </ReactMarkdown>
                                            </div>
                                        </div>
                                    </div>
                                )}
                            </div>
                        </div>
                    );
                })}

                {loading && (
                    <div className="flex justify-start animate-fadeIn">
                        <div className="bg-industrial-800/60 backdrop-blur-sm p-3 rounded-2xl rounded-bl-md border border-industrial-700/50 flex items-center gap-2.5">
                            <div className="flex gap-1">
                                <div className="w-1.5 h-1.5 bg-petro-500 rounded-full animate-bounce" style={{ animationDelay: '0ms' }}></div>
                                <div className="w-1.5 h-1.5 bg-petro-500 rounded-full animate-bounce" style={{ animationDelay: '150ms' }}></div>
                                <div className="w-1.5 h-1.5 bg-petro-500 rounded-full animate-bounce" style={{ animationDelay: '300ms' }}></div>
                            </div>
                            <span className="text-xs text-gray-400">
                                {useRLM ? 'Deep researching...' : 'Thinking...'}
                            </span>
                        </div>
                    </div>
                )}
                <div ref={messagesEndRef} />
            </div>

            {/* Input Area */}
            <div className="p-3 bg-gradient-to-t from-industrial-950 to-industrial-900/80 border-t border-industrial-700/50 backdrop-blur-md shrink-0">
                <div className="flex gap-2 items-center bg-industrial-800/50 border border-industrial-700/50 rounded-xl p-2 focus-within:border-petro-600/50 focus-within:shadow-lg focus-within:shadow-petro-900/20 transition-all duration-300">
                    <textarea
                        value={input}
                        onChange={(e) => setInput(e.target.value)}
                        onKeyDown={handleKeyDown}
                        placeholder="Ask a question about the document..."
                        className="flex-1 bg-transparent text-white text-sm focus:outline-none resize-none h-[40px] custom-scrollbar placeholder-gray-500"
                    />
                    <div className="flex items-center gap-1.5 border-l border-industrial-700/50 pl-2">
                        <button
                            onClick={() => setUseRLM(!useRLM)}
                            className={`p-2 rounded-lg transition-all duration-300 ${useRLM
                                ? 'bg-petro-600/30 text-petro-400 shadow-lg shadow-petro-900/30 border border-petro-600/30'
                                : 'text-gray-500 hover:text-gray-300 hover:bg-industrial-700/50 border border-transparent'
                                }`}
                            title={useRLM ? "Disable Deep Research" : "Enable Deep Research (RLM)"}
                        >
                            <Icons.Database className={`w-4 h-4 ${useRLM ? 'animate-pulse' : ''}`} />
                        </button>
                        <button
                            onClick={handleSend}
                            disabled={!input.trim() || loading}
                            className="p-2 bg-gradient-to-r from-petro-600 to-petro-500 hover:from-petro-500 hover:to-petro-400 text-white rounded-lg disabled:opacity-50 disabled:cursor-not-allowed transition-all duration-300 shadow-lg shadow-petro-900/40 hover:shadow-petro-800/50 disabled:shadow-none"
                            title="Send Message"
                        >
                            <Icons.MessageSquare className="w-4 h-4" />
                        </button>
                    </div>
                </div>
            </div>
        </div>
    );
};

export default ChatInterface;