import { API_BASE_URL, getSession, clearSession } from '@/services/api.uts'
import { APP_ENVIRONMENT } from '@/services/config.uts'

export type ReportDownload = { cancel: () => void, done: Promise<string> }

// #ifdef MP-WEIXIN
let previewFiles: string[] = []
const cleanPreviewFiles = () => {
    previewFiles = previewFiles.filter((path: string): boolean => {
        try { uni.getFileSystemManager().unlinkSync(path); return false } catch (_err) { return true }
    })
}
// 系统文档预览期间保留临时文件，返回小程序后清理；不调用saveFile持久化报告。
uni.onAppShow(() => cleanPreviewFiles())
// #endif

export function downloadReportPdf(id: string, revisionId: string = ''): ReportDownload {
    // #ifndef H5 || MP-WEIXIN
    return { cancel: () => {}, done: new Promise<string>((_resolve, reject) => { reject(new Error('当前客户端暂未开放PDF下载，请在普通浏览器打开H5并登录后下载。')) }) }
    // #endif
    // #ifdef MP-WEIXIN
    cleanPreviewFiles()
    let cancelled = false; let opening = false; let settled = false
    let task: DownloadTask | null = null; let tempPath = ''; let rejectDownload: ((error: Error) => void) | null = null
    const removeTemp = () => {
        if (tempPath.length == 0) return
        try { uni.getFileSystemManager().unlinkSync(tempPath) } catch (_err) { previewFiles.push(tempPath) }
        tempPath = ''
    }
    const fail = (message: string) => {
        removeTemp()
        if (settled) return
        settled = true; rejectDownload?.(new Error(message))
    }
    const stop = (message: string) => { fail(message); task?.abort() }
    const cancel = () => {
        // openDocument已经接管文件后，原页面可能隐藏/销毁，不能中止或删除正在预览的文件。
        if (opening || settled) return
        cancelled = true; stop('下载已取消。')
    }
    const done = new Promise<string>((resolve, reject) => {
        rejectDownload = reject
        if (!/^[1-9][0-9]{0,9}$/.test(id) || (revisionId.length > 0 && !/^[1-9][0-9]{0,9}$/.test(revisionId))) { fail('报告或版本编号无效，请重新打开本人报告。'); return }
        const token = getSession()?.getString('token') ?? ''
        if (token.length == 0) { fail('登录已过期，请重新登录后下载。'); return }
        if (!API_BASE_URL.startsWith('https://')) { fail('小程序PDF下载需要配置HTTPS服务地址。'); return }
        const current = (): boolean => {
            if (settled) return false
            if (cancelled || getSession()?.getString('token') != token) { fail('页面或登录状态已变化，本次下载已取消。'); return false }
            return true
        }
        let mime = ''; let declaredSize = 0; let encoded = false
        task = uni.downloadFile({
            url: API_BASE_URL + '/assessments/' + id + '/report.pdf' + (revisionId.length > 0 ? '?revisionId=' + encodeURIComponent(revisionId) : ''),
            header: { Authorization: 'Bearer ' + token, 'X-Requested-With': 'XMLHttpRequest' }, timeout: 45000,
            success: (response) => {
                tempPath = response.tempFilePath
                if (!current()) { removeTemp(); return }
                if (response.statusCode == 401) { clearSession(); fail('登录已过期，请重新登录后下载。'); return }
                try {
                    const fs = uni.getFileSystemManager()
                    const size = (fs.statSync(tempPath, false) as UniNamespace.Stats).size
                    if (response.statusCode != 200 || mime != 'application/pdf') {
                        let message = 'PDF暂不可下载，请稍后重试；已保存报告不受影响。'
                        if (mime == 'application/json' && size > 0 && size <= 8192) {
                            const body = JSON.parse<UTSJSONObject>(fs.readFileSync(tempPath, 'utf8') as string)
                            const serverMessage = body?.getString('msg') ?? ''
                            if (serverMessage.length > 0 && serverMessage.length < 200) message = serverMessage
                        }
                        fail(message); return
                    }
                    if (size > 20971520) { fail('PDF文件过大，请联系管理员。'); return }
                    if (size < 100 || (!encoded && declaredSize > 0 && declaredSize != size)) { fail('下载内容不是完整PDF，请重试。'); return }
                    // 只读取头尾，避免将整份报告加载到小程序内存。
                    const start = fs.readFileSync(tempPath, 'ascii', 0, 5) as string
                    const tailLength = Math.min(size, 1024)
                    const end = fs.readFileSync(tempPath, 'ascii', size - tailLength, tailLength) as string
                    if (start != '%PDF-' || !end.includes('%%EOF')) { fail('下载内容不是完整PDF，请重试。'); return }
                    if (!current()) return
                    opening = true
                    uni.openDocument({ filePath: tempPath, fileType: 'pdf', showMenu: true,
                        success: () => {
                            if (!current()) return
                            previewFiles.push(tempPath); tempPath = ''; settled = true
                            resolve('PDF已打开，可通过右上角菜单保存或转发。')
                        }, fail: () => { opening = false; fail('PDF已下载但暂时无法打开，请重试或更新微信。') }
                    })
                } catch (_err) { fail('PDF文件读取失败或内容异常，请重试。') }
            },
            fail: (error) => {
                if (!current()) return
                const reason = error.errMsg ?? ''
                if (reason.includes('domain list')) fail('PDF下载域名未配置，请联系管理员。')
                else if (reason.includes('timeout')) fail('PDF生成超时，请稍后重试。')
                else fail('PDF下载失败，请检查网络后重试。')
            }
        })
        task!.onHeadersReceived((response) => {
            if (!current()) { task?.abort(); return }
            const header = response.header as UTSJSONObject
            Object.keys(header).forEach((key: string) => {
                const value = header[key]?.toString() ?? ''
                if (key.toLowerCase() == 'content-type') mime = value.split(';')[0].trim().toLowerCase()
                if (key.toLowerCase() == 'content-length') declaredSize = Number(value)
                if (key.toLowerCase() == 'content-encoding') encoded = value.length > 0 && value.toLowerCase() != 'identity'
            })
            if (declaredSize > 20971520) stop('PDF文件过大，请联系管理员。')
        })
        task!.onProgressUpdate((progress) => {
            if (!current()) { task?.abort(); return }
            if (progress.totalBytesWritten > 20971520 || progress.totalBytesExpectedToWrite > 20971520) stop('PDF文件过大，请联系管理员。')
        })
    })
    return { cancel, done }
    // #endif
    // #ifdef H5
    const controller = new AbortController()
    let cancelled = false
    const cancel = () => { cancelled = true; controller.abort() }
    const done = async (): Promise<string> => {
        if (!/^[1-9][0-9]{0,9}$/.test(id) || (revisionId.length > 0 && !/^[1-9][0-9]{0,9}$/.test(revisionId))) throw new Error('报告或版本编号无效，请重新打开本人报告。')
        if (/MicroMessenger/i.test(navigator.userAgent)) throw new Error('微信内浏览器暂不支持此下载。请点右上角菜单，选择“在浏览器打开”，登录后重新点击下载PDF。')
        const token = getSession()?.getString('token') ?? ''
        if (token.length == 0) throw new Error('登录已过期，请重新登录后下载。')
        if (API_BASE_URL.length == 0 || (APP_ENVIRONMENT == 'production' && !API_BASE_URL.startsWith('https://'))) throw new Error('下载服务地址尚未配置。')
        const current = () => {
            if (cancelled || getSession()?.getString('token') != token) throw new Error('页面或登录状态已变化，本次下载已取消。')
        }
        const timeout = setTimeout(() => controller.abort(), 45000)
        try {
            const response = await fetch(API_BASE_URL + '/assessments/' + id + '/report.pdf' + (revisionId.length > 0 ? '?revisionId=' + encodeURIComponent(revisionId) : ''), {
                method: 'GET', headers: { Authorization: 'Bearer ' + token, 'X-Requested-With': 'XMLHttpRequest' },
                cache: 'no-store', credentials: 'omit', redirect: 'error', signal: controller.signal
            })
            current()
            if (response == null) throw new Error('下载服务未返回文件，请重试。')
            if (response.status == 401) { clearSession(); throw new Error('登录已过期，请重新登录后下载。') }
            const mime = (response.headers.get('Content-Type') ?? '').split(';')[0].trim().toLowerCase()
            if (!response.ok || mime != 'application/pdf') {
                let message = 'PDF暂不可下载，请稍后重试；已保存报告不受影响。'
                if (mime == 'application/json') {
                    const body = await response.json()
                    if (typeof body.msg == 'string' && body.msg.length > 0 && body.msg.length < 200) message = body.msg
                }
                current(); throw new Error(message)
            }
            const declaredSize = Number(response.headers.get('Content-Length') ?? '0')
            if (declaredSize > 20971520) throw new Error('PDF文件过大，请联系管理员。')
            const bytes = await response.arrayBuffer()
            current()
            const start = new TextDecoder('ascii').decode(bytes.slice(0, 5))
            const end = new TextDecoder('ascii').decode(bytes.slice(Math.max(0, bytes.byteLength - 1024)))
            const encoded = (response.headers.get('Content-Encoding') ?? '').toLowerCase()
            if (bytes.byteLength < 100 || bytes.byteLength > 20971520 || ((encoded.length == 0 || encoded == 'identity') && declaredSize > 0 && declaredSize != bytes.byteLength) || start != '%PDF-' || !end.includes('%%EOF')) throw new Error('下载内容不是完整PDF，请重试。')
            // 验证响应后才创建本机Blob。令牌只放请求头，不写URL、文件名或本机存储。
            const url = URL.createObjectURL(new Blob([bytes], { type: 'application/pdf' }))
            const link = document.createElement('a')
            link.href = url; link.download = 'financing-report-' + id + '.pdf'; link.style.display = 'none'
            document.body.appendChild(link); link.click(); link.remove()
            setTimeout(() => URL.revokeObjectURL(url), 1000)
            return 'PDF已交给浏览器处理，请查看下载列表；若打开预览，可使用浏览器的保存功能。'
        } catch (err) {
            if (cancelled) throw new Error('下载已取消。')
            if (controller.signal.aborted) throw new Error('PDF生成超时，请稍后重试。')
            if (err instanceof TypeError) throw new Error('网络连接失败，请检查网络后重试。')
            throw err
        } finally { clearTimeout(timeout) }
    }
    return { cancel, done: done() }
    // #endif
}