/*
 * Copyright (C) 2016-2020  Alex Yatskov <alex@foosoft.net>
 * Author: Alex Yatskov <alex@foosoft.net>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

/*global dictFieldSplit, dictTagSanitize, JSZip*/

class Database {
    constructor() {
        this.db = null;
    }

    async prepare() {
        if (this.db !== null) {
            throw new Error('Database already initialized');
        }

        try {
            this.db = await Database.open('dict', 5, (db, transaction, oldVersion) => {
                Database.upgrade(db, transaction, oldVersion, [
                    {
                        version: 2,
                        stores: {
                            terms: {
                                primaryKey: {keyPath: 'id', autoIncrement: true},
                                indices: ['dictionary', 'expression', 'reading']
                            },
                            kanji: {
                                primaryKey: {autoIncrement: true},
                                indices: ['dictionary', 'character']
                            },
                            tagMeta: {
                                primaryKey: {autoIncrement: true},
                                indices: ['dictionary']
                            },
                            dictionaries: {
                                primaryKey: {autoIncrement: true},
                                indices: ['title', 'version']
                            }
                        }
                    },
                    {
                        version: 3,
                        stores: {
                            termMeta: {
                                primaryKey: {autoIncrement: true},
                                indices: ['dictionary', 'expression']
                            },
                            kanjiMeta: {
                                primaryKey: {autoIncrement: true},
                                indices: ['dictionary', 'character']
                            },
                            tagMeta: {
                                primaryKey: {autoIncrement: true},
                                indices: ['dictionary', 'name']
                            }
                        }
                    },
                    {
                        version: 4,
                        stores: {
                            terms: {
                                primaryKey: {keyPath: 'id', autoIncrement: true},
                                indices: ['dictionary', 'expression', 'reading', 'sequence']
                            }
                        }
                    },
                    {
                        version: 5,
                        stores: {
                            terms: {
                                primaryKey: {keyPath: 'id', autoIncrement: true},
                                indices: ['dictionary', 'expression', 'reading', 'sequence', 'expressionReverse', 'readingReverse']
                            }
                        }
                    }
                ]);
            });
            return true;
        } catch (e) {
            console.error(e);
            return false;
        }
    }

    async close() {
        this.validate();
        this.db.close();
        this.db = null;
    }

    async purge() {
        this.validate();

        this.db.close();
        await Database.deleteDatabase(this.db.name);
        this.db = null;

        await this.prepare();
    }

    async deleteDictionary(dictionaryName, onProgress, progressSettings) {
        this.validate();

        const targets = [
            ['dictionaries', 'title'],
            ['kanji', 'dictionary'],
            ['kanjiMeta', 'dictionary'],
            ['terms', 'dictionary'],
            ['termMeta', 'dictionary'],
            ['tagMeta', 'dictionary']
        ];
        const promises = [];
        const progressData = {
            count: 0,
            processed: 0,
            storeCount: targets.length,
            storesProcesed: 0
        };
        let progressRate = (typeof progressSettings === 'object' && progressSettings !== null ? progressSettings.rate : 0);
        if (typeof progressRate !== 'number' || progressRate <= 0) {
            progressRate = 1000;
        }

        for (const [objectStoreName, index] of targets) {
            const dbTransaction = this.db.transaction([objectStoreName], 'readwrite');
            const dbObjectStore = dbTransaction.objectStore(objectStoreName);
            const dbIndex = dbObjectStore.index(index);
            const only = IDBKeyRange.only(dictionaryName);
            promises.push(Database.deleteValues(dbObjectStore, dbIndex, only, onProgress, progressData, progressRate));
        }

        await Promise.all(promises);
    }

    async findTermsBulk(termList, titles, wildcard) {
        this.validate();

        const promises = [];
        const visited = {};
        const results = [];
        const processRow = (row, index) => {
            if (titles.includes(row.dictionary) && !hasOwn(visited, row.id)) {
                visited[row.id] = true;
                results.push(Database.createTerm(row, index));
            }
        };

        const useWildcard = !!wildcard;
        const prefixWildcard = wildcard === 'prefix';

        const dbTransaction = this.db.transaction(['terms'], 'readonly');
        const dbTerms = dbTransaction.objectStore('terms');
        const dbIndex1 = dbTerms.index(prefixWildcard ? 'expressionReverse' : 'expression');
        const dbIndex2 = dbTerms.index(prefixWildcard ? 'readingReverse' : 'reading');

        for (let i = 0; i < termList.length; ++i) {
            const term = prefixWildcard ? stringReverse(termList[i]) : termList[i];
            const query = useWildcard ? IDBKeyRange.bound(term, `${term}\uffff`, false, false) : IDBKeyRange.only(term);
            promises.push(
                Database.getAll(dbIndex1, query, i, processRow),
                Database.getAll(dbIndex2, query, i, processRow)
            );
        }

        await Promise.all(promises);

        return results;
    }

    async findTermsExactBulk(termList, readingList, titles) {
        this.validate();

        const promises = [];
        const results = [];
        const processRow = (row, index) => {
            if (row.reading === readingList[index] && titles.includes(row.dictionary)) {
                results.push(Database.createTerm(row, index));
            }
        };

        const dbTransaction = this.db.transaction(['terms'], 'readonly');
        const dbTerms = dbTransaction.objectStore('terms');
        const dbIndex = dbTerms.index('expression');

        for (let i = 0; i < termList.length; ++i) {
            const only = IDBKeyRange.only(termList[i]);
            promises.push(Database.getAll(dbIndex, only, i, processRow));
        }

        await Promise.all(promises);

        return results;
    }

    async findTermsBySequenceBulk(sequenceList, mainDictionary) {
        this.validate();

        const promises = [];
        const results = [];
        const processRow = (row, index) => {
            if (row.dictionary === mainDictionary) {
                results.push(Database.createTerm(row, index));
            }
        };

        const dbTransaction = this.db.transaction(['terms'], 'readonly');
        const dbTerms = dbTransaction.objectStore('terms');
        const dbIndex = dbTerms.index('sequence');

        for (let i = 0; i < sequenceList.length; ++i) {
            const only = IDBKeyRange.only(sequenceList[i]);
            promises.push(Database.getAll(dbIndex, only, i, processRow));
        }

        await Promise.all(promises);

        return results;
    }

    async findTermMetaBulk(termList, titles) {
        return this.findGenericBulk('termMeta', 'expression', termList, titles, Database.createTermMeta);
    }

    async findKanjiBulk(kanjiList, titles) {
        return this.findGenericBulk('kanji', 'character', kanjiList, titles, Database.createKanji);
    }

    async findKanjiMetaBulk(kanjiList, titles) {
        return this.findGenericBulk('kanjiMeta', 'character', kanjiList, titles, Database.createKanjiMeta);
    }

    async findGenericBulk(tableName, indexName, indexValueList, titles, createResult) {
        this.validate();

        const promises = [];
        const results = [];
        const processRow = (row, index) => {
            if (titles.includes(row.dictionary)) {
                results.push(createResult(row, index));
            }
        };

        const dbTransaction = this.db.transaction([tableName], 'readonly');
        const dbTerms = dbTransaction.objectStore(tableName);
        const dbIndex = dbTerms.index(indexName);

        for (let i = 0; i < indexValueList.length; ++i) {
            const only = IDBKeyRange.only(indexValueList[i]);
            promises.push(Database.getAll(dbIndex, only, i, processRow));
        }

        await Promise.all(promises);

        return results;
    }

    async findTagForTitle(name, title) {
        this.validate();

        let result = null;
        const dbTransaction = this.db.transaction(['tagMeta'], 'readonly');
        const dbTerms = dbTransaction.objectStore('tagMeta');
        const dbIndex = dbTerms.index('name');
        const only = IDBKeyRange.only(name);
        await Database.getAll(dbIndex, only, null, (row) => {
            if (title === row.dictionary) {
                result = row;
            }
        });

        return result;
    }

    async getDictionaryInfo() {
        this.validate();

        const results = [];
        const dbTransaction = this.db.transaction(['dictionaries'], 'readonly');
        const dbDictionaries = dbTransaction.objectStore('dictionaries');

        await Database.getAll(dbDictionaries, null, null, (info) => results.push(info));

        return results;
    }

    async getDictionaryCounts(dictionaryNames, getTotal) {
        this.validate();

        const objectStoreNames = [
            'kanji',
            'kanjiMeta',
            'terms',
            'termMeta',
            'tagMeta'
        ];
        const dbCountTransaction = this.db.transaction(objectStoreNames, 'readonly');

        const targets = [];
        for (const objectStoreName of objectStoreNames) {
            targets.push([
                objectStoreName,
                dbCountTransaction.objectStore(objectStoreName).index('dictionary')
            ]);
        }

        // Query is required for Edge, otherwise index.count throws an exception.
        const query1 = IDBKeyRange.lowerBound('', false);
        const totalPromise = getTotal ? Database.getCounts(targets, query1) : null;

        const counts = [];
        const countPromises = [];
        for (let i = 0; i < dictionaryNames.length; ++i) {
            counts.push(null);
            const index = i;
            const query2 = IDBKeyRange.only(dictionaryNames[i]);
            const countPromise = Database.getCounts(targets, query2).then((v) => counts[index] = v);
            countPromises.push(countPromise);
        }
        await Promise.all(countPromises);

        const result = {counts};
        if (totalPromise !== null) {
            result.total = await totalPromise;
        }
        return result;
    }

    async importDictionary(archive, progressCallback, details) {
        this.validate();

        const errors = [];
        const prefixWildcardsSupported = details.prefixWildcardsSupported;

        const maxTransactionLength = 1000;
        const bulkAdd = async (objectStoreName, items, total, current) => {
            const db = this.db;
            for (let i = 0; i < items.length; i += maxTransactionLength) {
                if (progressCallback) {
                    progressCallback(total, current + i / items.length);
                }

                try {
                    const count = Math.min(maxTransactionLength, items.length - i);
                    const transaction = db.transaction([objectStoreName], 'readwrite');
                    const objectStore = transaction.objectStore(objectStoreName);
                    await Database.bulkAdd(objectStore, items, i, count);
                } catch (e) {
                    errors.push(e);
                }
            }
        };

        const indexDataLoaded = async (summary) => {
            if (summary.version > 3) {
                throw new Error('Unsupported dictionary version');
            }

            const db = this.db;
            const dbCountTransaction = db.transaction(['dictionaries'], 'readonly');
            const dbIndex = dbCountTransaction.objectStore('dictionaries').index('title');
            const only = IDBKeyRange.only(summary.title);
            const count = await Database.getCount(dbIndex, only);

            if (count > 0) {
                throw new Error('Dictionary is already imported');
            }

            const transaction = db.transaction(['dictionaries'], 'readwrite');
            const objectStore = transaction.objectStore('dictionaries');
            await Database.bulkAdd(objectStore, [summary], 0, 1);
        };

        const termDataLoaded = async (summary, entries, total, current) => {
            const rows = [];
            if (summary.version === 1) {
                for (const [expression, reading, definitionTags, rules, score, ...glossary] of entries) {
                    rows.push({
                        expression,
                        reading,
                        definitionTags,
                        rules,
                        score,
                        glossary,
                        dictionary: summary.title
                    });
                }
            } else {
                for (const [expression, reading, definitionTags, rules, score, glossary, sequence, termTags] of entries) {
                    rows.push({
                        expression,
                        reading,
                        definitionTags,
                        rules,
                        score,
                        glossary,
                        sequence,
                        termTags,
                        dictionary: summary.title
                    });
                }
            }

            if (prefixWildcardsSupported) {
                for (const row of rows) {
                    row.expressionReverse = stringReverse(row.expression);
                    row.readingReverse = stringReverse(row.reading);
                }
            }

            await bulkAdd('terms', rows, total, current);
        };

        const termMetaDataLoaded = async (summary, entries, total, current) => {
            const rows = [];
            for (const [expression, mode, data] of entries) {
                rows.push({
                    expression,
                    mode,
                    data,
                    dictionary: summary.title
                });
            }

            await bulkAdd('termMeta', rows, total, current);
        };

        const kanjiDataLoaded = async (summary, entries, total, current)  => {
            const rows = [];
            if (summary.version === 1) {
                for (const [character, onyomi, kunyomi, tags, ...meanings] of entries) {
                    rows.push({
                        character,
                        onyomi,
                        kunyomi,
                        tags,
                        meanings,
                        dictionary: summary.title
                    });
                }
            } else {
                for (const [character, onyomi, kunyomi, tags, meanings, stats] of entries) {
                    rows.push({
                        character,
                        onyomi,
                        kunyomi,
                        tags,
                        meanings,
                        stats,
                        dictionary: summary.title
                    });
                }
            }

            await bulkAdd('kanji', rows, total, current);
        };

        const kanjiMetaDataLoaded = async (summary, entries, total, current) => {
            const rows = [];
            for (const [character, mode, data] of entries) {
                rows.push({
                    character,
                    mode,
                    data,
                    dictionary: summary.title
                });
            }

            await bulkAdd('kanjiMeta', rows, total, current);
        };

        const tagDataLoaded = async (summary, entries, total, current) => {
            const rows = [];
            for (const [name, category, order, notes, score] of entries) {
                const row = dictTagSanitize({
                    name,
                    category,
                    order,
                    notes,
                    score,
                    dictionary: summary.title
                });

                rows.push(row);
            }

            await bulkAdd('tagMeta', rows, total, current);
        };

        const result = await Database.importDictionaryZip(
            archive,
            indexDataLoaded,
            termDataLoaded,
            termMetaDataLoaded,
            kanjiDataLoaded,
            kanjiMetaDataLoaded,
            tagDataLoaded,
            details
        );

        return {result, errors};
    }

    validate() {
        if (this.db === null) {
            throw new Error('Database not initialized');
        }
    }

    static async importDictionaryZip(
        archive,
        indexDataLoaded,
        termDataLoaded,
        termMetaDataLoaded,
        kanjiDataLoaded,
        kanjiMetaDataLoaded,
        tagDataLoaded,
        details
    ) {
        const zip = await JSZip.loadAsync(archive);

        const indexFile = zip.files['index.json'];
        if (!indexFile) {
            throw new Error('No dictionary index found in archive');
        }

        const index = JSON.parse(await indexFile.async('string'));
        if (!index.title || !index.revision) {
            throw new Error('Unrecognized dictionary format');
        }

        const summary = {
            title: index.title,
            revision: index.revision,
            sequenced: index.sequenced,
            version: index.format || index.version,
            prefixWildcardsSupported: !!details.prefixWildcardsSupported
        };

        await indexDataLoaded(summary);

        const buildTermBankName      = (index) => `term_bank_${index + 1}.json`;
        const buildTermMetaBankName  = (index) => `term_meta_bank_${index + 1}.json`;
        const buildKanjiBankName     = (index) => `kanji_bank_${index + 1}.json`;
        const buildKanjiMetaBankName = (index) => `kanji_meta_bank_${index + 1}.json`;
        const buildTagBankName       = (index) => `tag_bank_${index + 1}.json`;

        const countBanks = (namer) => {
            let count = 0;
            while (zip.files[namer(count)]) {
                ++count;
            }

            return count;
        };

        const termBankCount      = countBanks(buildTermBankName);
        const termMetaBankCount  = countBanks(buildTermMetaBankName);
        const kanjiBankCount     = countBanks(buildKanjiBankName);
        const kanjiMetaBankCount = countBanks(buildKanjiMetaBankName);
        const tagBankCount       = countBanks(buildTagBankName);

        let bankLoadedCount = 0;
        let bankTotalCount =
            termBankCount +
            termMetaBankCount +
            kanjiBankCount +
            kanjiMetaBankCount +
            tagBankCount;

        if (tagDataLoaded && index.tagMeta) {
            const bank = [];
            for (const name in index.tagMeta) {
                const tag = index.tagMeta[name];
                bank.push([name, tag.category, tag.order, tag.notes, tag.score]);
            }

            tagDataLoaded(summary, bank, ++bankTotalCount, bankLoadedCount++);
        }

        const loadBank = async (summary, namer, count, callback) => {
            if (callback) {
                for (let i = 0; i < count; ++i) {
                    const bankFile = zip.files[namer(i)];
                    const bank = JSON.parse(await bankFile.async('string'));
                    await callback(summary, bank, bankTotalCount, bankLoadedCount++);
                }
            }
        };

        await loadBank(summary, buildTermBankName, termBankCount, termDataLoaded);
        await loadBank(summary, buildTermMetaBankName, termMetaBankCount, termMetaDataLoaded);
        await loadBank(summary, buildKanjiBankName, kanjiBankCount, kanjiDataLoaded);
        await loadBank(summary, buildKanjiMetaBankName, kanjiMetaBankCount, kanjiMetaDataLoaded);
        await loadBank(summary, buildTagBankName, tagBankCount, tagDataLoaded);

        return summary;
    }

    static createTerm(row, index) {
        return {
            index,
            expression: row.expression,
            reading: row.reading,
            definitionTags: dictFieldSplit(row.definitionTags || row.tags || ''),
            termTags: dictFieldSplit(row.termTags || ''),
            rules: dictFieldSplit(row.rules),
            glossary: row.glossary,
            score: row.score,
            dictionary: row.dictionary,
            id: row.id,
            sequence: typeof row.sequence === 'undefined' ? -1 : row.sequence
        };
    }

    static createKanji(row, index) {
        return {
            index,
            character: row.character,
            onyomi: dictFieldSplit(row.onyomi),
            kunyomi: dictFieldSplit(row.kunyomi),
            tags: dictFieldSplit(row.tags),
            glossary: row.meanings,
            stats: row.stats,
            dictionary: row.dictionary
        };
    }

    static createTermMeta({expression, mode, data, dictionary}, index) {
        return {expression, mode, data, dictionary, index};
    }

    static createKanjiMeta({character, mode, data, dictionary}, index) {
        return {character, mode, data, dictionary, index};
    }

    static getAll(dbIndex, query, context, processRow) {
        const fn = typeof dbIndex.getAll === 'function' ? Database.getAllFast : Database.getAllUsingCursor;
        return fn(dbIndex, query, context, processRow);
    }

    static getAllFast(dbIndex, query, context, processRow) {
        return new Promise((resolve, reject) => {
            const request = dbIndex.getAll(query);
            request.onerror = (e) => reject(e);
            request.onsuccess = (e) => {
                for (const row of e.target.result) {
                    processRow(row, context);
                }
                resolve();
            };
        });
    }

    static getAllUsingCursor(dbIndex, query, context, processRow) {
        return new Promise((resolve, reject) => {
            const request = dbIndex.openCursor(query, 'next');
            request.onerror = (e) => reject(e);
            request.onsuccess = (e) => {
                const cursor = e.target.result;
                if (cursor) {
                    processRow(cursor.value, context);
                    cursor.continue();
                } else {
                    resolve();
                }
            };
        });
    }

    static getCounts(targets, query) {
        const countPromises = [];
        const counts = {};
        for (const [objectStoreName, index] of targets) {
            const n = objectStoreName;
            const countPromise = Database.getCount(index, query).then((count) => counts[n] = count);
            countPromises.push(countPromise);
        }
        return Promise.all(countPromises).then(() => counts);
    }

    static getCount(dbIndex, query) {
        return new Promise((resolve, reject) => {
            const request = dbIndex.count(query);
            request.onerror = (e) => reject(e);
            request.onsuccess = (e) => resolve(e.target.result);
        });
    }

    static getAllKeys(dbIndex, query) {
        const fn = typeof dbIndex.getAllKeys === 'function' ? Database.getAllKeysFast : Database.getAllKeysUsingCursor;
        return fn(dbIndex, query);
    }

    static getAllKeysFast(dbIndex, query) {
        return new Promise((resolve, reject) => {
            const request = dbIndex.getAllKeys(query);
            request.onerror = (e) => reject(e);
            request.onsuccess = (e) => resolve(e.target.result);
        });
    }

    static getAllKeysUsingCursor(dbIndex, query) {
        return new Promise((resolve, reject) => {
            const primaryKeys = [];
            const request = dbIndex.openKeyCursor(query, 'next');
            request.onerror = (e) => reject(e);
            request.onsuccess = (e) => {
                const cursor = e.target.result;
                if (cursor) {
                    primaryKeys.push(cursor.primaryKey);
                    cursor.continue();
                } else {
                    resolve(primaryKeys);
                }
            };
        });
    }

    static async deleteValues(dbObjectStore, dbIndex, query, onProgress, progressData, progressRate) {
        const hasProgress = (typeof onProgress === 'function');
        const count = await Database.getCount(dbIndex, query);
        ++progressData.storesProcesed;
        progressData.count += count;
        if (hasProgress) {
            onProgress(progressData);
        }

        const onValueDeleted = (
            hasProgress ?
            () => {
                const p = ++progressData.processed;
                if ((p % progressRate) === 0 || p === progressData.count) {
                    onProgress(progressData);
                }
            } :
            () => {}
        );

        const promises = [];
        const primaryKeys = await Database.getAllKeys(dbIndex, query);
        for (const key of primaryKeys) {
            const promise = Database.deleteValue(dbObjectStore, key).then(onValueDeleted);
            promises.push(promise);
        }

        await Promise.all(promises);
    }

    static deleteValue(dbObjectStore, key) {
        return new Promise((resolve, reject) => {
            const request = dbObjectStore.delete(key);
            request.onerror = (e) => reject(e);
            request.onsuccess = () => resolve();
        });
    }

    static bulkAdd(objectStore, items, start, count) {
        return new Promise((resolve, reject) => {
            if (start + count > items.length) {
                count = items.length - start;
            }

            if (count <= 0) {
                resolve();
                return;
            }

            const end = start + count;
            let completedCount = 0;
            const onError = (e) => reject(e);
            const onSuccess = () => {
                if (++completedCount >= count) {
                    resolve();
                }
            };

            for (let i = start; i < end; ++i) {
                const request = objectStore.add(items[i]);
                request.onerror = onError;
                request.onsuccess = onSuccess;
            }
        });
    }

    static open(name, version, onUpgradeNeeded) {
        return new Promise((resolve, reject) => {
            const request = window.indexedDB.open(name, version * 10);

            request.onupgradeneeded = (event) => {
                try {
                    request.transaction.onerror = (e) => reject(e);
                    onUpgradeNeeded(request.result, request.transaction, event.oldVersion / 10, event.newVersion / 10);
                } catch (e) {
                    reject(e);
                }
            };

            request.onerror = (e) => reject(e);
            request.onsuccess = () => resolve(request.result);
        });
    }

    static upgrade(db, transaction, oldVersion, upgrades) {
        for (const {version, stores} of upgrades) {
            if (oldVersion >= version) { continue; }

            const objectStoreNames = Object.keys(stores);
            for (const objectStoreName of objectStoreNames) {
                const {primaryKey, indices} = stores[objectStoreName];

                const objectStoreNames = transaction.objectStoreNames || db.objectStoreNames;
                const objectStore = (
                    Database.listContains(objectStoreNames, objectStoreName) ?
                    transaction.objectStore(objectStoreName) :
                    db.createObjectStore(objectStoreName, primaryKey)
                );

                for (const indexName of indices) {
                    if (Database.listContains(objectStore.indexNames, indexName)) { continue; }

                    objectStore.createIndex(indexName, indexName, {});
                }
            }
        }
    }

    static deleteDatabase(dbName) {
        return new Promise((resolve, reject) => {
            const request = indexedDB.deleteDatabase(dbName);
            request.onerror = (e) => reject(e);
            request.onsuccess = () => resolve();
        });
    }

    static listContains(list, value) {
        for (let i = 0, ii = list.length; i < ii; ++i) {
            if (list[i] === value) { return true; }
        }
        return false;
    }
}