import React from "react";
import { FlatList, Pressable, View } from "react-native";
import { ActivityIndicator, Text } from "react-native-paper";
import { SafeAreaView } from "react-native-safe-area-context";
import { useNavigation } from "@react-navigation/native";
import { parseBibleReference } from "../utils/bibleReferences.js";
import GlobalState from "../contexts/GlobalState.js";

const BibleChapterView = ({ route }) => {
    const navigation = useNavigation();
    const reference = route?.params?.reference || "";
    const selectable = route?.params?.selectable === true;
    const { chapterReference, verse: selectedVerse } = parseBibleReference(reference);
    const [loading, setLoading] = React.useState(true);
    const [error, setError] = React.useState("");
    const [chapterData, setChapterData] = React.useState(null);
    const listRef = React.useRef(null);
    const autoScrolledRef = React.useRef(false);

    React.useEffect(() => {
        let mounted = true;
        const loadChapter = async () => {
            setLoading(true);
            setError("");
            try {
                const response = await fetch(`https://bible-api.com/${encodeURIComponent(chapterReference)}`);
                if (!response.ok) throw new Error("Failed chapter request");
                const payload = await response.json();
                if (!mounted) return;
                setChapterData(payload);
            } catch (_error) {
                if (!mounted) return;
                setError("Unable to load chapter.");
                setChapterData(null);
            } finally {
                if (mounted) setLoading(false);
            }
        };
        loadChapter();
        return () => {
            mounted = false;
        };
    }, [chapterReference]);

    const verses = Array.isArray(chapterData?.verses) ? chapterData.verses : [];
    const selectedVerseNumber = Number(selectedVerse || 1);
    const selectedIndex = verses.findIndex((item) => Number(item?.verse || 0) === selectedVerseNumber);

    React.useEffect(() => {
        autoScrolledRef.current = false;
    }, [chapterReference, selectedVerseNumber]);

    const scrollToSelectedVerse = React.useCallback((animated = false) => {
        if (autoScrolledRef.current) return;
        if (!listRef.current || selectedIndex < 0 || !verses.length) return;
        try {
            listRef.current.scrollToIndex({
                index: selectedIndex,
                animated,
                viewPosition: 0.35,
            });
            autoScrolledRef.current = true;
        } catch (_error) {
            // FlatList can throw before enough measurements are available.
        }
    }, [selectedIndex, verses.length]);

    if (loading) {
        return (
            <SafeAreaView style={{ flex: 1, justifyContent: "center", alignItems: "center" }}>
                <ActivityIndicator />
            </SafeAreaView>
        );
    }

    if (error) {
        return (
            <SafeAreaView style={{ flex: 1, justifyContent: "center", alignItems: "center", padding: 16 }}>
                <Text style={{ color: "#b91c1c" }}>{error}</Text>
            </SafeAreaView>
        );
    }

    const handleVersePress = (verseNumber) => {
        if (!selectable) return;
        GlobalState.bibleChapterSelection = {
            ...parseBibleReference(`${chapterReference}:${verseNumber}`),
            ts: Date.now(),
        };
        navigation.goBack();
    };

    return (
        <SafeAreaView style={{ flex: 1 }}>
        <View style={{ flex: 1, padding: 12 }}>
            <Text style={{ fontSize: 22, fontWeight: "700", marginBottom: 4 }}>
                {chapterData?.reference || chapterReference}
            </Text>
            <Text style={{ color: "#6b7280", marginBottom: 10 }}>
                {chapterData?.translation_name || chapterData?.translation_id || "KJV"}
            </Text>
            {selectable ? (
                <Text style={{ color: "#6b7280", marginBottom: 8 }}>Tap a verse to select it.</Text>
            ) : null}
            <FlatList
                ref={listRef}
                data={verses}
                keyExtractor={(item, idx) => `${item?.verse || idx}`}
                initialNumToRender={24}
                onLayout={() => {
                    setTimeout(() => scrollToSelectedVerse(false), 40);
                }}
                onContentSizeChange={() => {
                    setTimeout(() => scrollToSelectedVerse(false), 40);
                }}
                onScrollToIndexFailed={({ index, averageItemLength }) => {
                    if (!listRef.current) return;
                    listRef.current.scrollToOffset({
                        offset: Math.max(0, (averageItemLength || 36) * index),
                        animated: false,
                    });
                    setTimeout(() => {
                        scrollToSelectedVerse(false);
                    }, 120);
                }}
                renderItem={({ item }) => {
                    const verseNumber = Number(item?.verse || 0);
                    const isSelected = verseNumber === selectedVerseNumber;
                    return (
                        <Pressable
                            onPress={() => handleVersePress(verseNumber)}
                            style={{
                                paddingVertical: 8,
                                paddingHorizontal: 10,
                                borderRadius: 8,
                                marginBottom: 6,
                                backgroundColor: isSelected ? "#fff3cd" : "transparent",
                                borderWidth: isSelected ? 1 : 0,
                                borderColor: isSelected ? "#f59e0b" : "transparent",
                            }}
                        >
                            <Text style={{ fontWeight: "700", color: isSelected ? "#92400e" : "#374151" }}>
                                {verseNumber}
                            </Text>
                            <Text style={{ color: "#111827", lineHeight: 21 }}>{item?.text || ""}</Text>
                        </Pressable>
                    );
                }}
            />
        </View>
        </SafeAreaView>
    );
};

export default BibleChapterView;