import { MessageBubble } from '@/components/chat/MessageBubble';
import { TypingIndicator } from '@/components/chat/TypingIndicator';
import { ChatMessage } from '@/store/useAppStore';
import { findLastAssistantId, shouldShowTypingIndicator } from '@/utils/chatSelectors';
import React, { useEffect, useRef } from 'react';
import { FlatList, StyleSheet } from 'react-native';
import Animated, { FadeInDown } from 'react-native-reanimated';

interface MessageListProps {
    messages: ChatMessage[];
    isStreaming: boolean;
    onEdit: (id: string) => void;
    onDelete: (id: string) => void;
    onRegenerate: () => void;
}

interface MessageRowProps {
    message: ChatMessage;
    delayed: boolean;
    isStreaming: boolean;
    isLastAssistant: boolean;
    onEdit: (id: string) => void;
    onDelete: (id: string) => void;
    onRegenerate: () => void;
}

// Memoized so that a streamed token only re-renders (and re-parses the Markdown of)
// the message that changed, not the whole conversation.
const MessageRow = React.memo(function MessageRow({
    message,
    delayed,
    isStreaming,
    isLastAssistant,
    onEdit,
    onDelete,
    onRegenerate,
}: MessageRowProps) {
    return (
        <Animated.View entering={FadeInDown.duration(300).delay(delayed ? 100 : 0)}>
            <MessageBubble
                message={message}
                onEdit={() => onEdit(message.id)}
                onRegenerate={onRegenerate}
                onDelete={() => onDelete(message.id)}
                isStreaming={isStreaming}
                isLastAssistant={isLastAssistant}
            />
        </Animated.View>
    );
});

export function MessageList({ messages, isStreaming, onEdit, onDelete, onRegenerate }: MessageListProps) {
    const flatListRef = useRef<FlatList>(null);
    const lastAssistantId = findLastAssistantId(messages);
    const lastContentLength = messages[messages.length - 1]?.content?.length;

    useEffect(() => {
        if (messages.length > 0 && flatListRef.current) {
            setTimeout(() => {
                flatListRef.current?.scrollToEnd({ animated: !isStreaming });
            }, 100);
        }
    }, [messages.length, lastContentLength, isStreaming]);

    return (
        <>
            <FlatList
                ref={flatListRef}
                data={messages}
                keyExtractor={(item) => item.id}
                renderItem={({ item, index }) => (
                    <MessageRow
                        message={item}
                        delayed={index > messages.length - 4}
                        isStreaming={isStreaming}
                        isLastAssistant={item.id === lastAssistantId}
                        onEdit={onEdit}
                        onDelete={onDelete}
                        onRegenerate={onRegenerate}
                    />
                )}
                contentContainerStyle={styles.listContent}
            />
            {shouldShowTypingIndicator(messages, isStreaming) && <TypingIndicator />}
        </>
    );
}

const styles = StyleSheet.create({
    listContent: {
        paddingTop: 16,
        paddingBottom: 24,
    },
});