const axios = require('axios')
const HttpsProxyAgent = require('https-proxy-agent')
const QgProxyManager = require('./QgProxyManager')

function sleep(ms) {
    return new Promise(r => setTimeout(r, ms))
}

/** 外层再包几轮：应对瞬时 NO_AVAILABLE_CHANNEL、网络抖动 */
async function getOutboundWithBackoff(qgOpts, rounds = 5) {
    let lastErr
    for (let i = 0; i < rounds; i++) {
        try {
            if (i > 0) await sleep(380 * i * i)
            return await QgProxyManager.getOutboundAxiosFragment(qgOpts)
        } catch (e) {
            lastErr = e
        }
    }
    throw lastErr
}

/**
 * Axios 对「HTTPS 目标 + 内置 proxy」在部分环境下会引发 ERR_FR_TOO_MANY_REDIRECTS，
 * 改用 HttpsProxyAgent 走 CONNECT 隧道。
 */
function buildAxiosOutboundConfig(fragment) {
    if (!fragment || fragment.proxy === false || !fragment.proxy) {
        return { proxy: false }
    }
    const { host, port, auth } = fragment.proxy
    let userPart = ''
    if (auth && String(auth.username || '').length > 0) {
        const u = encodeURIComponent(auth.username)
        const p = encodeURIComponent(auth.password != null ? String(auth.password) : '')
        userPart = `${u}:${p}@`
    }
    const proxyUrl = `http://${userPart}${host}:${port}`
    return {
        proxy: false,
        httpsAgent: new HttpsProxyAgent(proxyUrl)
    }
}

function debugProxyEnabled() {
    return String(process.env.LEPAO_DEBUG_PROXY || '').trim() === '1'
}

function debugProxyAxiosFragment() {
    const host = process.env.LEPAO_DEBUG_PROXY_HOST || '127.0.0.1'
    const port = Number(process.env.LEPAO_DEBUG_PROXY_PORT || 9000)
    return {
        proxy: {
            host,
            port,
            protocol: 'http'
        }
    }
}

function briefUrlPath(fullUrl) {
    try {
        const u = new URL(fullUrl)
        return `${u.pathname}${u.search}`
    } catch {
        return fullUrl
    }
}

function isQgProxyEligibleFailure(err) {
    if (!err) return false
    const status = err.response?.status
    if (status === 407) return true
    if (status === 502 || status === 503 || status === 504) return true
    if (
        err.code &&
        ['ECONNRESET', 'ECONNABORTED', 'ETIMEDOUT', 'ENOTFOUND', 'EAI_AGAIN', 'ECONNREFUSED', 'EPROTO', 'ERR_FR_TOO_MANY_REDIRECTS'].includes(
            err.code
        )
    ) {
        return true
    }
    if (err.isAxiosError && !err.response) return true
    const msg = (err.message || '').toLowerCase()
    if (msg.includes('timeout') || msg.includes('socket') || msg.includes('network')) return true
    return false
}

function summarizeAxiosError(err) {
    if (!err) return {}
    return {
        message: err.message,
        code: err.code,
        status: err.response?.status,
        isAxiosError: err.isAxiosError
    }
}

/**
 * @param {*} logger Worker logger 或 null
 * @param {{ skipQgSnapshot?: boolean }} opts 为 true 时仅用 axios 配置的 host:port（如 Charles）
 */
async function logSchoolOutbound(logger, phase, url, axiosMerge, opts = {}) {
    if (!logger?.info) return
    const path = briefUrlPath(url)
    if (!axiosMerge || axiosMerge.proxy === false || !axiosMerge.proxy) {
        logger.info(`[lepaoSchoolHttp] ${phase} 对学校 POST 出站=直连 path=${path}`)
        return
    }
    const conn = `${axiosMerge.proxy.host}:${axiosMerge.proxy.port}`
    if (opts.skipQgSnapshot) {
        logger.info(
            `[lepaoSchoolHttp] ${phase} 对学校 POST 出站=调试HTTP代理（非青果） 连接=${conn} path=${path}`
        )
        return
    }
    const snap = await QgProxyManager.getCachedParsed()
    const serverRecord = snap?.server ?? conn
    const egress = snap?.proxyIp ?? '（暂无 proxy_ip）'
    const dl = snap?.deadline ?? '—'
    logger.info(
        `[lepaoSchoolHttp] ${phase} 对学校 POST 出站=HTTP代理 节点server=${serverRecord} 连接${conn} 出口IP(proxy_ip)=${egress} deadline=${dl} path=${path}`
    )
}

/**
 * 对学校 lepao.ctbu.edu.cn 的 POST：优先青果代理；失败轮换一次；再失败直连并记日志。
 */
async function postLepaoSchool(url, data, options = {}) {
    const { headers = {}, timeout = 15000, logger = null } = options

    const doPost = async (qgProxyFragment) => {
        const outbound = buildAxiosOutboundConfig(qgProxyFragment)
        return axios.post(url, data, {
            headers,
            timeout,
            ...outbound
        })
    }

    if (debugProxyEnabled()) {
        const dbg = debugProxyAxiosFragment()
        await logSchoolOutbound(logger, 'Charles调试代理', url, dbg, { skipQgSnapshot: true })
        logger?.info?.('[lepaoSchoolHttp] 使用本地调试代理 LEPAO_DEBUG_PROXY')
        return doPost(dbg)
    }

    const qgOn = await QgProxyManager.isOutboundProxyEnabled()
    if (!qgOn) {
        await logSchoolOutbound(logger, '（青果出站未启用）', url, { proxy: false })
        return doPost({ proxy: false })
    }

    let frag
    try {
        frag = await getOutboundWithBackoff({ forceRefresh: false }, 5)
    } catch (e0) {
        logger?.error?.(`[lepaoSchoolHttp] 青果提取多次重试仍失败，改直连: ${e0.message || e0}`)
        await logSchoolOutbound(logger, '（青果提取异常→直连）', url, { proxy: false })
        await QgProxyManager.recordFallbackDirect({
            reason: 'qg_extract_error',
            ...summarizeAxiosError(e0)
        })
        return doPost({ proxy: false })
    }

    if (frag.proxy === false) {
        try {
            await sleep(600)
            frag = await getOutboundWithBackoff({ forceRefresh: true }, 4)
        } catch {
            /* 保持 frag 原状 */
        }
    }

    if (frag.proxy === false) {
        logger?.warn?.('[lepaoSchoolHttp] 无可用青果节点，对学校 POST 将直连')
        await logSchoolOutbound(logger, '（无缓存节点→直连）', url, { proxy: false })
        await QgProxyManager.recordFallbackDirect({ reason: 'no_proxy_available' })
        return doPost({ proxy: false })
    }

    await logSchoolOutbound(logger, '首次请求', url, frag)
    try {
        return await doPost(frag)
    } catch (e1) {
        if (!isQgProxyEligibleFailure(e1)) throw e1
        logger?.warn?.(
            `[lepaoSchoolHttp] 经代理首次请求失败，将作废IP并换新。err=${e1.message || e1} ${JSON.stringify(summarizeAxiosError(e1))}`
        )
        await QgProxyManager.invalidateCurrent('request_fail', summarizeAxiosError(e1))

        // 通道数为 1 时，服务端释放上一 IP 需要时间；与 QgProxyManager 内 /get 多轮重试配合
        await sleep(1400)

        let frag2
        try {
            frag2 = await getOutboundWithBackoff({ forceRefresh: true }, 5)
        } catch (eFetch) {
            logger?.warn?.(`[lepaoSchoolHttp] 换新 IP 提取失败：${eFetch.message || eFetch}`)
            await logSchoolOutbound(logger, '（换新提取失败→将加试直连前再试）', url, { proxy: false })
            frag2 = { proxy: false }
        }

        if (frag2.proxy === false) {
            frag2 = null
        }

        if (frag2) {
            await logSchoolOutbound(logger, '换新IP重试', url, frag2)
            try {
                return await doPost(frag2)
            } catch (e2) {
                if (!isQgProxyEligibleFailure(e2)) throw e2
                logger?.warn?.(
                    `[lepaoSchoolHttp] 换新IP后仍失败，将进入加试阶段。err=${e2.message || e2} ${JSON.stringify(
                        summarizeAxiosError(e2)
                    )}`
                )
                await QgProxyManager.invalidateCurrent('retry_round_post_fail', summarizeAxiosError(e2))
            }
        }

        for (let extra = 0; extra < 5; extra++) {
            await sleep(750 + 400 * extra * extra)
            try {
                const fragX = await getOutboundWithBackoff({ forceRefresh: true }, 5)
                if (fragX.proxy === false) continue
                await logSchoolOutbound(logger, `补充轮次-${extra + 1}`, url, fragX)
                try {
                    return await doPost(fragX)
                } catch (e4) {
                    if (!isQgProxyEligibleFailure(e4)) throw e4
                    await QgProxyManager.invalidateCurrent('extra_round_fail', summarizeAxiosError(e4))
                }
            } catch (eGrab) {
                logger?.warn?.(`[lepaoSchoolHttp] 补充轮提取失败 (${extra + 1}): ${eGrab.message || eGrab}`)
            }
        }

        logger?.warn?.(`[lepaoSchoolHttp] 多轮代理均不可用，回退直连 path=${briefUrlPath(url)}`)
        await logSchoolOutbound(logger, '（多轮失败后→直连）', url, { proxy: false })
        await QgProxyManager.recordFallbackDirect({
            reason: 'exhausted_proxy_then_direct',
            message: lastNote()
        })
        return doPost({ proxy: false })
    }
}

function lastNote() {
    return '已用尽提取与 POST 加试仍失败或未取到可用节点'
}

module.exports = {
    postLepaoSchool,
    isQgProxyEligibleFailure,
    debugProxyEnabled,
    debugProxyAxiosFragment
}