/**
 * 下载管理工具
 * 文件保存到公共下载目录，用户可通过文件管理器访问
 */

const STORAGE_KEY = 'localDownloads'
const SUB_DIR = 'AppDownloads' // 公共下载目录下的子文件夹

/**
 * 获取公共下载目录路径
 * @returns {Promise<string>} 下载目录绝对路径
 */
function getPublicDownloadDir() {
	return new Promise((resolve, reject) => {
		// #ifdef APP-PLUS
		plus.io.requestFileSystem(
			plus.io.PUBLIC_DOWNLOADS,
			(fs) => {
				// PUBLIC_DOWNLOADS 对应 /storage/emulated/0/Download/
				fs.root.getDirectory(
					SUB_DIR,
					{ create: true },
					(dirEntry) => {
						resolve(dirEntry.fullPath)
					},
					(err) => {
						console.error('getDirectory failed:', err)
						reject(err)
					}
				)
			},
			(err) => {
				console.error('requestFileSystem failed:', err)
				reject(err)
			}
		)
		// #endif
		// #ifndef APP-PLUS
		reject(new Error('仅APP端支持'))
		// #endif
	})
}

/**
 * 从完整路径中提取可读的显示路径
 * 如 /storage/emulated/0/Download/AppDownloads/xxx.pdf → 下载/AppDownloads/xxx.pdf
 */
function getDisplayPath(fullPath) {
	const idx = fullPath.indexOf('/Download/')
	if (idx !== -1) {
		return '下载/' + fullPath.slice(idx + 10)
	}
	return fullPath
}

/**
 * 获取所有下载记录
 * @returns {Array} 下载记录列表
 */
export function getDownloadList() {
	try {
		return uni.getStorageSync(STORAGE_KEY) || []
	} catch (e) {
		return []
	}
}

/**
 * 保存下载记录（复制到公共下载目录）
 * @param {string} tempFilePath 临时文件路径（uni.downloadFile 返回的）
 * @param {string} fileName     文件名
 * @param {number} fileSize     文件大小（字节，可选）
 */
export function saveDownload(tempFilePath, fileName, fileSize) {
	return new Promise((resolve, reject) => {
		// #ifdef APP-PLUS
		getPublicDownloadDir().then((dirPath) => {
			const destPathForUrl = plus.io.convertLocalFileSystemURL(dirPath + '/' + fileName)

			plus.io.resolveLocalFileSystemURL(
				tempFilePath,
				(fileEntry) => {
					plus.io.resolveLocalFileSystemURL(
						dirPath,
						(dirEntry) => {
							fileEntry.copyTo(
								dirEntry,
								fileName,
								() => {
									const record = {
										id: Date.now().toString(),
										name: fileName,
										path: destPathForUrl,
										displayPath: getDisplayPath(destPathForUrl),
										size: fileSize || 0,
										time: Date.now()
									}
									const list = getDownloadList()
									const exists = list.some(item => item.name === fileName)
									if (exists) {
										const idx = list.findIndex(item => item.name === fileName)
										if (idx !== -1) list.splice(idx, 1)
									}
									list.unshift(record)
									try {
										uni.setStorageSync(STORAGE_KEY, list)
									} catch (e) {
										list.pop()
										uni.setStorageSync(STORAGE_KEY, list)
									}
									resolve(record)
								},
								(err) => {
									console.error('copyTo failed:', err)
									reject(err)
								}
							)
						},
						reject
					)
				},
				reject
			)
		}).catch(reject)
		// #endif
		// #ifndef APP-PLUS
		// 非 APP 端降级使用 uni.saveFile
		uni.saveFile({
			tempFilePath: tempFilePath,
			success: (saveRes) => {
				const record = {
					id: Date.now().toString(),
					name: fileName,
					path: saveRes.savedFilePath,
					size: fileSize || 0,
					time: Date.now()
				}
				const list = getDownloadList()
				list.unshift(record)
				uni.setStorageSync(STORAGE_KEY, list)
				resolve(record)
			},
			fail: reject
		})
		// #endif
	})
}

/**
 * 删除单条下载记录及其文件
 * @param {string} id 记录 ID
 */
export function deleteDownload(id) {
	return new Promise((resolve, reject) => {
		const list = getDownloadList()
		const record = list.find(item => item.id === id)
		if (!record) {
			reject(new Error('记录不存在'))
			return
		}

		// #ifdef APP-PLUS
		// 删除公共目录下的文件
		plus.io.resolveLocalFileSystemURL(
			record.path,
			(fileEntry) => {
				fileEntry.remove(
					() => {
						const newList = list.filter(item => item.id !== id)
						uni.setStorageSync(STORAGE_KEY, newList)
						resolve()
					},
					() => {
						// 文件不存在也清除记录
						const newList = list.filter(item => item.id !== id)
						uni.setStorageSync(STORAGE_KEY, newList)
						resolve()
					}
				)
			},
			() => {
				// 无法解析路径，直接清除记录
				const newList = list.filter(item => item.id !== id)
				uni.setStorageSync(STORAGE_KEY, newList)
				resolve()
			}
		)
		// #endif
		// #ifndef APP-PLUS
		uni.removeSavedFile({
			filePath: record.path,
			success: () => {
				const newList = list.filter(item => item.id !== id)
				uni.setStorageSync(STORAGE_KEY, newList)
				resolve()
			},
			fail: () => {
				const newList = list.filter(item => item.id !== id)
				uni.setStorageSync(STORAGE_KEY, newList)
				resolve()
			}
		})
		// #endif
	})
}

/**
 * 清空所有下载记录和文件
 */
export function clearAllDownloads() {
	return new Promise((resolve) => {
		const list = getDownloadList()
		if (list.length === 0) {
			resolve()
			return
		}

		// #ifdef APP-PLUS
		let count = 0
		const done = () => {
			count++
			if (count >= list.length) {
				uni.setStorageSync(STORAGE_KEY, [])
				resolve()
			}
		}

		list.forEach(record => {
			plus.io.resolveLocalFileSystemURL(
				record.path,
				(fileEntry) => {
					fileEntry.remove(done, done)
				},
				done
			)
		})

		setTimeout(() => {
			uni.setStorageSync(STORAGE_KEY, [])
			resolve()
		}, 5000)
		// #endif
		// #ifndef APP-PLUS
		let count = 0
		list.forEach(record => {
			uni.removeSavedFile({
				filePath: record.path,
				success: () => { count++; if (count >= list.length) { uni.setStorageSync(STORAGE_KEY, []); resolve() } },
				fail: () => { count++; if (count >= list.length) { uni.setStorageSync(STORAGE_KEY, []); resolve() } }
			})
		})
		if (list.length === 0) resolve()
		setTimeout(() => { uni.setStorageSync(STORAGE_KEY, []); resolve() }, 3000)
		// #endif
	})
}

/**
 * 格式化文件大小为可读字符串
 * @param {number} bytes 字节数
 * @returns {string}
 */
export function formatFileSize(bytes) {
	if (!bytes || bytes <= 0) return '未知大小'
	const units = ['B', 'KB', 'MB', 'GB']
	let i = 0
	let size = bytes
	while (size >= 1024 && i < units.length - 1) {
		size /= 1024
		i++
	}
	return size.toFixed(i === 0 ? 0 : 1) + ' ' + units[i]
}

/**
 * 格式化时间戳为可读日期
 * @param {number} timestamp
 * @returns {string}
 */
export function formatTime(timestamp) {
	const d = new Date(timestamp)
	const pad = n => String(n).padStart(2, '0')
	return `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())} ${pad(d.getHours())}:${pad(d.getMinutes())}`
}