/* ===== Batch Selection & Actions ===== */
window.NAIBatch = {
    /**
     * Create a batch controller for a gallery page.
     * @param {object} opts
     *   - gridSel: grid container selector
     *   - toolbarSel: toolbar container selector
     *   - getItems: () => [{id, ...}] all items
     *   - renderCard: (item, isSelected, batchMode) => HTMLElement
     *   - onDelete: async (ids) => void
     *   - onDownload: async (ids) => void  (optional, we provide default ZIP)
     *   - getImageB64: async (id) => {b64, filename}
     *   - getName: (item) => string filename
     */
    create(opts) {
        const ctrl = {
            opts,
            batchMode: false,
            selected: new Set(),

            toggle() {
                this.batchMode = !this.batchMode;
                if (!this.batchMode) this.selected.clear();
                this.updateToolbar();
                this.refreshGrid();
            },

            selectAll() {
                const items = this.opts.getItems();
                items.forEach(item => this.selected.add(item.id ?? item.path));
                this.updateToolbar();
                this.refreshGrid();
            },

            selectNone() {
                this.selected.clear();
                this.updateToolbar();
                this.refreshGrid();
            },

            toggleItem(id) {
                if (this.selected.has(id)) {
                    this.selected.delete(id);
                } else {
                    this.selected.add(id);
                }
                this.updateToolbar();
                // Update just the card
                const card = document.querySelector(`[data-batch-id="${id}"]`);
                if (card) {
                    card.classList.toggle('batch-selected', this.selected.has(id));
                    const cb = card.querySelector('.batch-checkbox');
                    if (cb) cb.checked = this.selected.has(id);
                }
            },

            // Shift-click range select
            _lastClickedId: null,
            rangeSelect(id) {
                const items = this.opts.getItems();
                const ids = items.map(i => i.id ?? i.path);
                const curIdx = ids.indexOf(id);
                const lastIdx = ids.indexOf(this._lastClickedId);
                if (lastIdx === -1 || curIdx === -1) {
                    this.toggleItem(id);
                    this._lastClickedId = id;
                    return;
                }
                const start = Math.min(curIdx, lastIdx);
                const end = Math.max(curIdx, lastIdx);
                for (let i = start; i <= end; i++) {
                    this.selected.add(ids[i]);
                }
                this._lastClickedId = id;
                this.updateToolbar();
                this.refreshGrid();
            },

            updateToolbar() {
                const toolbar = document.querySelector(this.opts.toolbarSel);
                if (!toolbar) return;

                if (!this.batchMode) {
                    toolbar.style.display = 'none';
                    return;
                }

                toolbar.style.display = 'flex';
                const count = this.selected.size;
                const total = this.opts.getItems().length;

                const countEl = toolbar.querySelector('.batch-count');
                if (countEl) countEl.textContent = `已选 ${count} / ${total}`;

                const allCb = toolbar.querySelector('.batch-select-all');
                if (allCb) {
                    allCb.checked = count > 0 && count === total;
                    allCb.indeterminate = count > 0 && count < total;
                }

                // Disable actions when nothing selected
                toolbar.querySelectorAll('.batch-action-btn').forEach(btn => {
                    btn.disabled = count === 0;
                });
            },

            refreshGrid() {
                // Re-render grid via the host page
                if (this.opts.onRefreshGrid) this.opts.onRefreshGrid();
            },

            async batchDelete() {
                const count = this.selected.size;
                if (count === 0) return;
                if (!confirm(`确定删除选中的 ${count} 张图片？`)) return;

                const ids = [...this.selected];
                try {
                    await this.opts.onDelete(ids);
                    this.selected.clear();
                    this.updateToolbar();
                } catch(e) {
                    console.error('Batch delete failed:', e);
                    alert('部分删除失败，请重试');
                }
            },

            async batchDownload() {
                const count = this.selected.size;
                if (count === 0) return;

                const ids = [...this.selected];
                const toolbar = document.querySelector(this.opts.toolbarSel);
                const progressEl = toolbar?.querySelector('.batch-progress');

                // Use JSZip to create ZIP in browser
                if (typeof JSZip === 'undefined') {
                    alert('JSZip 未加载，无法打包下载');
                    return;
                }

                const zip = new JSZip();
                let loaded = 0;

                if (progressEl) {
                    progressEl.style.display = '';
                    progressEl.textContent = `打包中 0/${count}`;
                }

                for (const id of ids) {
                    try {
                        const result = await this.opts.getImageB64(id);
                        if (result && result.b64) {
                            zip.file(result.filename, result.b64, { base64: true });
                        }
                    } catch(e) {
                        console.error('Failed to fetch image:', id, e);
                    }
                    loaded++;
                    if (progressEl) progressEl.textContent = `打包中 ${loaded}/${count}`;
                }

                if (progressEl) progressEl.textContent = '生成ZIP...';

                try {
                    const blob = await zip.generateAsync({
                        type: 'blob',
                        compression: 'STORE',
                    }, (meta) => {
                        if (progressEl) progressEl.textContent = `压缩 ${Math.round(meta.percent)}%`;
                    });

                    const url = URL.createObjectURL(blob);
                    const a = document.createElement('a');
                    a.href = url;
                    const now = new Date();
                    a.download = `nai_batch_${now.getFullYear()}${String(now.getMonth()+1).padStart(2,'0')}${String(now.getDate()).padStart(2,'0')}.zip`;
                    document.body.appendChild(a);
                    a.click();
                    document.body.removeChild(a);
                    URL.revokeObjectURL(url);
                } catch(e) {
                    console.error('ZIP generation failed:', e);
                    alert('ZIP生成失败');
                }

                if (progressEl) {
                    progressEl.textContent = '完成';
                    setTimeout(() => { progressEl.style.display = 'none'; }, 2000);
                }
            },
        };

        return ctrl;
    },
};