import { Charset, Index } from './thirdparty/flexsearch.bundle.module.min.js'
import { settingValues } from "./settings.js";

// --- Constants ---

// Tag data sources
export const TagSource = {
    Danbooru: 'danbooru',
    E621: 'e621',
}

export const TagCategory = {
    'danbooru': [
        'general',
        'artist',
        'unused',
        'copyright',
        'character',
        'meta',
    ],
    'e621': [
        'general',
        'artist',
        'unused',
        'copyright',
        'character',
        'species',
        'invalid',
        'meta',
        'lore',
    ]
}

// --- Data Structures ---

/**
 * Class representing a tag and its metadata
 */
export class TagData {
    /**
     * Create a tag data object
     * @param {string} tag - The tag name
     * @param {string[]} [alias=[]] - Array of aliases for the tag
     * @param {string} [category='general'] - Category of the tag
     * @param {number} [count=0] - Frequency count/popularity of the tag
     * @param {string} [source=TagSources.Danbooru] - The source of the tag data
     */
    constructor(tag, alias = [], category = 'general', count = 0, source = TagSource.Danbooru) {
        /** @type {string} */
        this.tag = tag;

        /** @type {string[]} */
        this.alias = alias;

        /** @type {string} */
        this.category = category;

        /** @type {number} */
        this.count = count;

        this.source = source;
    }
}

class AutocompleteData {
    constructor() {
        /** @type {Index} */
        this.flexSearchIndex = null;

        /** @type {TagData[]} */
        this.sortedTags = [];

        /** @type {Map<string, TagData>} */
        this.tagMap = new Map();

        /** @type {Map<string, TagData>} */
        this.aliasMap = new Map();

        /** @type {Map<string, Map<string, number>>} */
        this.cooccurrenceMap = new Map();

        this.isInitializing = false;
        this.initialized = false;

        // Progress of "base" csv loading
        this.baseLoadingProgress = {
            // tags: 0,
            cooccurrence: 0
        };
    }
}

/**
 * @type {Object<string, AutocompleteData>}
 */
export const autoCompleteData = {};

// CSV Header for tags
const TAGS_CSV_HEADER = 'tag,category,count,alias';
const TAGS_CSV_HEADER_COLUMNS = TAGS_CSV_HEADER.split(',');
const TAG_INDEX = TAGS_CSV_HEADER_COLUMNS.indexOf('tag');
const ALIAS_INDEX = TAGS_CSV_HEADER_COLUMNS.indexOf('alias');
const CATEGORY_INDEX = TAGS_CSV_HEADER_COLUMNS.indexOf('category');
const COUNT_INDEX = TAGS_CSV_HEADER_COLUMNS.indexOf('count');

// --- Helder Functions ---

/**
 * Get the available tag sources in priority order based on the current settings.
 * @returns {string[]} Array of available tag sources in priority order
 */
export function getEnabledTagSourceInPriorityOrder() {
    return Object.values(TagSource)
        .filter((s) => {
            return settingValues.tagSource === s || settingValues.tagSource === 'all';
        })
        .toSorted((a, b) => {
            return a === settingValues.primaryTagSource ? -1 : 1;
        });
}

// --- Data Loading Functions ---

/**
 * Loads tag data from a single CSV file.
 * @param {string} csvUrl - The URL of the CSV file to load.
 * @param {string} siteName - The site name (e.g., 'danbooru', 'e621').
 * @returns {Promise<void>}
 */
async function loadTags(csvUrl, siteName) {
    try {
        const response = await fetch(csvUrl, { cache: "no-store" });
        if (!response.ok) {
            throw new Error(`HTTP error! status: ${response.status}`);
        }
        const csvText = await response.text();
        const lines = csvText.split('\n').filter(line => line.trim().length > 0);
        const totalLines = lines.length;

        const startIndex = lines[0].toLowerCase().startsWith(TAGS_CSV_HEADER) ? 1 : 0;

        for (let i = startIndex; i < lines.length; i++) {
            const line = lines[i];
            const columns = parseCSVLine(line);

            if (columns.length === TAGS_CSV_HEADER_COLUMNS.length) {
                const tag = columns[TAG_INDEX].trim();
                const aliasStr = columns[ALIAS_INDEX].trim();
                const category = columns[CATEGORY_INDEX].trim();
                const count = parseInt(columns[COUNT_INDEX].trim(), 10);

                if (!tag || isNaN(count)) continue;

                // Skip if tag already exists (priority to earlier loaded files - extra then base)
                if (autoCompleteData[siteName].tagMap.has(tag)) {
                    continue;
                }

                // Parse aliases - might be comma-separated list inside quotes
                const aliases = aliasStr ? aliasStr.split(',').map(a => a.trim()).filter(a => a.length > 0) : [];

                // Create a TagData instance instead of a plain object
                const tagData = new TagData(tag, aliases, category, count, siteName);

                autoCompleteData[siteName].sortedTags.push(tagData);
            } else {
                console.warn(`[Autocomplete-Plus] Invalid CSV format in line ${i + 1} of ${csvUrl}: ${line}. Expected ${TAGS_CSV_HEADER_COLUMNS.length} columns, but got ${columns.length}.`);
                continue;
            }
        }

        // Sort by count in descending order
        autoCompleteData[siteName].sortedTags.sort((a, b) => b.count - a.count);

        // Build maps as before, but ensure not to overwrite if already processed from extra files
        autoCompleteData[siteName].sortedTags.forEach(tagData => {
            if (!autoCompleteData[siteName].tagMap.has(tagData.tag)) {
                autoCompleteData[siteName].tagMap.set(tagData.tag, tagData);
                if (tagData.alias && Array.isArray(tagData.alias)) {
                    tagData.alias.forEach(alias => {
                        if (!autoCompleteData[siteName].aliasMap.has(alias)) {
                            autoCompleteData[siteName].aliasMap.set(alias, tagData.tag); // Map alias back to the main tag
                        }
                    });
                }
            }
        });

    } catch (error) {
        console.error(`[Autocomplete-Plus] Failed to fetch or process tags from ${csvUrl}:`, error);
    }
}

/**
 * Build FlexSearch index for the given site name.
 * @param {string} siteName 
 */
async function buildFlexSearchIndex(siteName) {
    try {
        const index = new Index({
            tokenize: "forward",
            // encoder: Charset.CJK, // FIXME: English search doesn't work properly when using CJK
        });

        let startIdx = 0;
        const startTime = performance.now();
        function processChunkTasks() {
            const chunkSize = 1000;
            const end = Math.min(startIdx + chunkSize, autoCompleteData[siteName].sortedTags.length);
            for (; startIdx < end; startIdx++) {
                const tagData = autoCompleteData[siteName].sortedTags[startIdx];
                let allTags = [];
                allTags.push(tagData.tag);
                if (tagData.alias && Array.isArray(tagData.alias)) {
                    tagData.alias.forEach(alias => {
                        allTags.push(alias);
                    });
                }
                allTags = [...new Set(allTags)];
                index.add(startIdx, allTags.join(','));
            }

            if (startIdx < autoCompleteData[siteName].sortedTags.length) {
                setTimeout(processChunkTasks, 0);
                // console.log(`[Autocomplete-Plus] Current porcess: ${startIdx}`);
            } else {
                const endTime = performance.now();
                const duration = endTime - startTime;
                autoCompleteData[siteName].flexSearchIndex = index;
                console.debug(`[Autocomplete-Plus] Building ${autoCompleteData[siteName].sortedTags.length} index for ${siteName} took ${duration.toFixed(2)}ms.`);
            }
        }
        processChunkTasks();
    } catch (error) {
        console.error(`[Autocomplete-Plus] Failed to building flexSearch index`, error);
    }
}

/**
 * Loads co-occurrence data from a single CSV file.
 * @param {string} csvUrl - The URL of the CSV file to load.
 * @param {string} siteName - The site name (e.g., 'danbooru', 'e621').
 * @returns {Promise<void>}
 */
async function loadCooccurrence(csvUrl, siteName) {
    try {
        const response = await fetch(csvUrl, { cache: "no-store" });
        if (!response.ok) {
            throw new Error(`HTTP error! status: ${response.status}`);
        }

        const csvText = await response.text();
        const lines = csvText.split('\n').filter(line => line.trim().length > 0);

        const startIndex = lines[0].startsWith('tag_a,tag_b,count') ? 1 : 0;

        await processInChunks(lines, startIndex, autoCompleteData[siteName].cooccurrenceMap, csvUrl, siteName);
    } catch (error) {
        console.error(`[Autocomplete-Plus] Failed to fetch or process cooccurrence data from ${csvUrl}:`, error);
    }
}

/**
 * Process CSV data in chunks to avoid blocking the UI.
 * Modifies the targetMap directly.
 */
function processInChunks(lines, startIndex, targetMap, csvUrl, siteName) {
    return new Promise((resolve) => {
        const CHUNK_SIZE = 10000;
        let i = startIndex;
        let pairCount = 0;

        function processChunk() {
            const endIndex = Math.min(i + CHUNK_SIZE, lines.length);

            for (; i < endIndex; i++) {
                const line = lines[i];
                const columns = parseCSVLine(line);

                if (columns.length >= 3) {
                    const tagA = columns[0].trim();
                    const tagB = columns[1].trim();
                    const count = parseInt(columns[2].trim(), 10);

                    if (!tagA || !tagB || isNaN(count)) continue;

                    // Add tagA -> tagB relationship
                    if (!targetMap.has(tagA)) {
                        targetMap.set(tagA, new Map());
                    }
                    targetMap.get(tagA).set(tagB, count);


                    // Add tagB -> tagA relationship (bidirectional)
                    if (!targetMap.has(tagB)) {
                        targetMap.set(tagB, new Map());
                    }
                    targetMap.get(tagB).set(tagA, count);

                    pairCount++;
                }
            }

            if (i < lines.length) {
                autoCompleteData[siteName].baseLoadingProgress.cooccurrence = Math.round((i / lines.length) * 100);
                setTimeout(processChunk, 0);
            } else {
                resolve();
            }
        }

        processChunk();
    });
}

/**
 * Parse a CSV line properly, handling quoted values that may contain commas.
 * @param {string} line A single CSV line
 * @returns {string[]} Array of column values
 */
function parseCSVLine(line) {
    const result = [];
    let current = '';
    let inQuotes = false;

    for (let i = 0; i < line.length; i++) {
        const char = line[i];

        if (char === '"') {
            if (inQuotes && i + 1 < line.length && line[i + 1] === '"') {
                current += '"';
                i++;
            } else {
                inQuotes = !inQuotes;
            }
        } else if (char === ',' && !inQuotes) {
            result.push(current);
            current = '';
        } else {
            current += char;
        }
    }

    result.push(current);

    return result;
}

export async function fetchCsvList() {
    try {
        const response = await fetch('/autocomplete-plus/csv');
        if (!response.ok) {
            throw new Error(`[Autocomplete-Plus] Failed to fetch CSV list: ${response.status} ${response.statusText}`);
        }
        return await response.json();
    } catch (error) {
        console.error("[Autocomplete-Plus] Error fetch csv data:", error);
    }

    return null;
}

/**
 * Initializes the autocomplete data by fetching the list of CSV files and loading them.
 * This function is called when the extension is initialized.
 */
export async function initializeData(csvListData, source) {
    if (autoCompleteData.hasOwnProperty(source) === false) {
        autoCompleteData[source] = new AutocompleteData();
    }

    if (autoCompleteData[source].isInitializing || autoCompleteData[source].initialized) {
        return;
    }

    const startTime = performance.now();
    autoCompleteData[source].isInitializing = true;
    // console.log("[Autocomplete-Plus] Initializing autocomplete data...");

    try {
        // Store functions that return Promises (Promise Factories)
        // These factories will be called later to start the actual loading.
        const tagsLoadPromiseFactories = [];
        const cooccurrenceLoadPromiseFactories = [];

        // Check if siteName exists in csvListData to prevent errors if a sourte is removed or misconfigured
        if (!csvListData[source]) {
            console.warn(`[Autocomplete-Plus] CSV list data not found for sourte: ${source}. Skipping.`);
            return;
        }

        const extraTagsFileList = csvListData[source].extra_tags || [];
        const extraCooccurrenceFileList = csvListData[source].extra_cooccurrence || [];

        const tagsUrl = `/autocomplete-plus/csv/${source}/tags`;
        const cooccurrenceUrl = `/autocomplete-plus/csv/${source}/tags_cooccurrence`;

        // Factory for loading tags for the current sourte
        const siteTagsLoaderFactory = async () => {
            let promiseChain = Promise.resolve();
            for (let i = 0; i < extraTagsFileList.length; i++) {
                promiseChain = promiseChain.then(() => loadTags(`${tagsUrl}/extra/${i}`, source));
            }
            if (csvListData[source].base_tags) {
                promiseChain = promiseChain.then(() => loadTags(`${tagsUrl}/base`, source));
            }
            return promiseChain;
        };
        tagsLoadPromiseFactories.push(siteTagsLoaderFactory);

        // Factory for loading cooccurrence data for the current sourte
        const siteCooccurrenceLoaderFactory = async () => {
            let promiseChain = Promise.resolve();
            for (let i = 0; i < extraCooccurrenceFileList.length; i++) {
                promiseChain = promiseChain.then(() => loadCooccurrence(`${cooccurrenceUrl}/extra/${i}`, source));
            }
            if (csvListData[source].base_cooccurrence) {
                promiseChain = promiseChain.then(() => loadCooccurrence(`${cooccurrenceUrl}/base`, source));
            }
            return promiseChain;
        };
        cooccurrenceLoadPromiseFactories.push(siteCooccurrenceLoaderFactory);

        // Now, execute all promise factories and wait for their completion.
        // The actual loading (fetch calls) will start when the factories are invoked here.
        await Promise.all([
            Promise.all(tagsLoadPromiseFactories.map(factory => factory()))
                .then(() => {
                    // Build FlexSearch index after tags are loaded
                    return buildFlexSearchIndex(source);
                })
                .then(() => {
                    const endTime = performance.now();
                    if (csvListData[source].base_tags) {
                        console.log(`[Autocomplete-Plus] "${source}" Tags loading complete in ${(endTime - startTime).toFixed(2)}ms`);
                    }
                }),
            Promise.all(cooccurrenceLoadPromiseFactories.map(factory => factory())).then(() => {
                const endTime = performance.now();
                if (csvListData[source].base_cooccurrence) {
                    console.log(`[Autocomplete-Plus] "${source}" Co-occurrence loading complete in ${(endTime - startTime).toFixed(2)}ms.`);
                }
            })
        ]);

        autoCompleteData[source].initialized = true;
    } catch (error) {
        console.error("[Autocomplete-Plus] Error initializing autocomplete data:", error);
    } finally {
        autoCompleteData[source].isInitializing = false;
    }
}