/** 拼接 API 根路径与相对路径，避免双斜杠 */
export function joinApiUrl(base, path) {
    const b = String(base || '').replace(/\/+$/, '')
    const p = String(path || '').replace(/^\/+/, '')
    return p ? `${b}/${p}` : b
}

function appendQuery(url, data) {
    if (!data || typeof data !== 'object') return url
    const keys = Object.keys(data)
    if (!keys.length) return url
    const qs = keys
        .map((k) => `${encodeURIComponent(k)}=${encodeURIComponent(data[k] ?? '')}`)
        .join('&')
    return url + (url.includes('?') ? '&' : '?') + qs
}

function decodeChunkData(data) {
    if (typeof data === 'string') return data
    if (!data) return ''
    if (typeof TextDecoder !== 'undefined' && data instanceof ArrayBuffer) {
        return new TextDecoder('utf-8').decode(new Uint8Array(data))
    }
    if (data instanceof ArrayBuffer) {
        const bytes = new Uint8Array(data)
        let str = ''
        for (let i = 0; i < bytes.length; i++) str += String.fromCharCode(bytes[i])
        try {
            return decodeURIComponent(escape(str))
        } catch (e) {
            return str
        }
    }
    return ''
}

/** 从 SSE 文本缓冲中解析并消费完整事件 */
export function consumeSseBuffer(buffer, onEvent) {
    let rest = buffer
    let idx = rest.indexOf('\n\n')
    while (idx !== -1) {
        const block = rest.slice(0, idx)
        rest = rest.slice(idx + 2)
        let event = 'message'
        let dataLine = ''
        block.split('\n').forEach((line) => {
            if (line.startsWith('event:')) event = line.slice(6).trim()
            else if (line.startsWith('data:')) dataLine += line.slice(5).trim()
        })
        if (dataLine) {
            try {
                onEvent(event, JSON.parse(dataLine))
            } catch (e) {
                onEvent(event, dataLine)
            }
        }
        idx = rest.indexOf('\n\n')
    }
    return rest
}

/** 从流式纯文本中提取三餐（支持未写完的最后一行） */
export function parsePartialDietPlainText(text) {
    const out = {}
    if (!text) return out

    const lineRe = /^(早餐|午餐|晚餐|提示|少碰)[：:]\s*(.*)$/gm
    let match
    while ((match = lineRe.exec(text)) !== null) {
        const key = { '早餐': 'breakfast', '午餐': 'lunch', '晚餐': 'dinner', '提示': 'tips', '少碰': 'avoid' }[match[1]]
        const val = (match[2] || '').trim()
        if (key === 'avoid') {
            out.avoid = val.split(/[、,，;；\s]+/).map((s) => s.trim()).filter(Boolean)
        } else {
            out[key] = val
        }
    }

    const tail = text.match(/(?:^|\n)(早餐|午餐|晚餐|提示|少碰)[：:]\s*([^\n]*)$/)
    if (tail) {
        const key = { '早餐': 'breakfast', '午餐': 'lunch', '晚餐': 'dinner', '提示': 'tips', '少碰': 'avoid' }[tail[1]]
        const val = (tail[2] || '').trim()
        if (key === 'avoid') {
            if (val) out.avoid = val.split(/[、,，;；\s]+/).map((s) => s.trim()).filter(Boolean)
        } else {
            out[key] = val
        }
    }

    return out
}

/** @deprecated 使用 parsePartialDietPlainText */
export function parsePartialDietJson(text) {
    return parsePartialDietPlainText(text)
}

/**
 * SSE 流式请求（微信小程序 enableChunked；其它端走 fallback）
 *
 * @param {object} opts
 * @param {string} opts.baseUrl
 * @param {string} opts.url
 * @param {string} [opts.method]
 * @param {object} [opts.data]
 * @param {function(string, object):void} opts.onEvent
 * @param {function():Promise<object>} [opts.fallback] 不支持流式时的降级请求
 */
export function requestAiStream(opts) {
    const {
        baseUrl,
        url,
        method = 'GET',
        data = {},
        onEvent,
        fallback
    } = opts

    // #ifdef MP-WEIXIN
    return new Promise((resolve, reject) => {
        const token = uni.getStorageSync('token') || ''
        let sseBuffer = ''
        let requestUrl = joinApiUrl(baseUrl, url)
        if (method === 'GET') {
            requestUrl = appendQuery(requestUrl, data)
        }

        const task = wx.request({
            url: requestUrl,
            method,
            data: method === 'POST' ? data : {},
            enableChunked: true,
            timeout: 60000,
            header: {
                token,
                'content-type': 'application/x-www-form-urlencoded',
                'Cache-Control': 'no-cache'
            },
            success: (res) => {
                if (res && res.data) {
                    sseBuffer += decodeChunkData(res.data)
                    sseBuffer = consumeSseBuffer(sseBuffer, onEvent)
                }
                resolve(res)
            },
            fail: (err) => reject(err)
        })

        if (task && typeof task.onChunkReceived === 'function') {
            task.onChunkReceived((res) => {
                sseBuffer += decodeChunkData(res.data)
                sseBuffer = consumeSseBuffer(sseBuffer, onEvent)
            })
        } else if (typeof fallback === 'function') {
            fallback().then(resolve).catch(reject)
        } else {
            reject(new Error('当前环境不支持流式请求'))
        }
    })
    // #endif

    // #ifndef MP-WEIXIN
    if (typeof fallback === 'function') {
        return fallback()
    }
    return Promise.reject(new Error('当前环境不支持流式请求'))
    // #endif
}