-- file: lua/backend-baidu.lua
-- 终极修复：针对红果短剧独立验证机制 + UDP免流量伪装

local http = require 'http'
local backend = require 'backend'

local char = string.char
local byte = string.byte
local find = string.find
local sub = string.sub
local gsub = string.gsub
local lower = string.lower

local ADDRESS = backend.ADDRESS
local PROXY = backend.PROXY
local DIRECT_WRITE = backend.SUPPORT.DIRECT_WRITE

local SUCCESS = backend.RESULT.SUCCESS
local HANDSHAKE = backend.RESULT.HANDSHAKE
local DIRECT = backend.RESULT.DIRECT

local ctx_uuid = backend.get_uuid
local ctx_proxy_type = backend.get_proxy_type
local ctx_address_type = backend.get_address_type
local ctx_address_host = backend.get_address_host
local ctx_address_bytes = backend.get_address_bytes
local ctx_address_port = backend.get_address_port
local ctx_write = backend.write
local ctx_free = backend.free
local ctx_debug = backend.debug

-- 新增：UDP相关
local ctx_is_udp = backend.get_is_udp or function() return false end  -- 兼容旧版

local flags = {}
local kHttpHeaderSent = 1
local kHttpHeaderRecived = 2

-- 红果/字节系视频域名特征
local HK_DOMAINS = {
    "zijie", "hongguo", "novel", "pangolin", "sigmob",
    "amemv", "douyin", "iesdouyin", "byteimg",
    "toutiao", "ixigua", "snssdk", "bdurl",
}

function is_hongguo_target(host)
    local h = lower(host)
    for _, v in ipairs(HK_DOMAINS) do
        if find(h, v, 1, true) then
            return true
        end
    end
    return false
end

-- 判断是否需要UDP免流伪装（可自行扩展域名/IP）
function is_udp_masquerade_target(host)
    if not host then return true end
    local h = lower(host)
    -- 常见游戏/UDP高频域名，可继续添加
    local udp_targets = {"udp", "quic", "game", "minecraft", "dota", "lol", "valorant", "genshin"}
    for _, v in ipairs(udp_targets) do
        if find(h, v, 1, true) then
            return true
        end
    end
    return true  -- 默认全部UDP都做伪装
end

function wa_lua_on_flags_cb(ctx)
    return DIRECT_WRITE
end

function wa_lua_on_handshake_cb(ctx)
    local uuid = ctx_uuid(ctx)
    local is_udp = ctx_is_udp(ctx)

    if flags[uuid] == kHttpHeaderRecived then
        return true
    end

    if flags[uuid] ~= kHttpHeaderSent then
        local host = ctx_address_host(ctx)
        local port = ctx_address_port(ctx)
        local addr_type = ctx_address_type(ctx)
        
        local is_hg = is_hongguo_target(host)
        local do_udp_mask = is_udp and is_udp_masquerade_target(host)
        
        ctx_debug("CONNECT to " .. host .. ":" .. port .. 
                 " hg=" .. tostring(is_hg) .. 
                 " udp=" .. tostring(is_udp) .. 
                 " mask=" .. tostring(do_udp_mask))

        local res

        if do_udp_mask then
            -- ==================== UDP免流量伪装核心 ====================
            -- 模拟百度网盘/百度系内部UDP转发特征（更难被识别）
            res = 'CONNECT ' .. host .. ':' .. port .. ' HTTP/1.1\r\n' ..
                  'Host: 153.3.236.22:443\r\n' ..
                  'Proxy-Connection: Keep-Alive\r\n' ..
                  'Connection: keep-alive\r\n' ..
                  'X-T5-Auth: 683556433\r\n' ..
                  'User-Agent: baiduboxapp/8.0.0.0 (Linux; Android)\r\n' ..
                  'X-Bd-Traceid: 0000000000000000000000000000000000000000\r\n' ..
                  'X-Bd-Product: BDUSS\r\n' ..
                  'X-Bd-Uid: 0\r\n' ..
                  'X-Bd-Client-Type: UDP-TRANS\r\n' ..           -- UDP特征标识
                  'X-Bd-Trans-Type: masquerade\r\n' ..            -- 伪装标识
                  'X-Bd-Request-Mode: tunnel\r\n' ..
                  'Accept: */*\r\n' ..
                  'Content-Length: 0\r\n' ..
                  '\r\n'
        elseif is_hg then
            -- 红果目标：TCP加强版伪装
            res = 'CONNECT ' .. host .. ':' .. port .. ' HTTP/1.1\r\n' ..
                  'Host: 153.3.236.22:443\r\n' ..
                  'Proxy-Connection: Keep-Alive\r\n' ..
                  'Connection: keep-alive\r\n' ..
                  'X-T5-Auth: 683556433\r\n' ..
                  'User-Agent: baiduboxapp\r\n' ..
                  'X-Bd-Traceid: 0000000000000000000000000000000000000000\r\n' ..
                  'X-Bd-Product: BDUSS\r\n' ..
                  'X-Bd-Uid: 0\r\n' ..
                  'Accept: */*\r\n' ..
                  '\r\n'
        else
            -- 普通TCP
            res = 'CONNECT ' .. host .. ':' .. port .. ' HTTP/1.1\r\n' ..
                  'Host: 153.3.236.22:443\r\n' ..
                  'Proxy-Connection: Keep-Alive\r\n' ..
                  'Connection: keep-alive\r\n' ..
                  'X-T5-Auth: 683556433\r\n' ..
                  'User-Agent: baiduboxapp\r\n' ..
                  '\r\n'
        end
        
        ctx_write(ctx, res)
        flags[uuid] = kHttpHeaderSent
    end

    return false
end

function wa_lua_on_read_cb(ctx, buf)
    local uuid = ctx_uuid(ctx)
    
    if flags[uuid] == kHttpHeaderSent then
        flags[uuid] = kHttpHeaderRecived
        return HANDSHAKE, nil
    end
    
    if buf == nil then
        return DIRECT, nil
    end
    
    if #buf == 0 then
        return DIRECT, ''
    end

    -- UDP伪装模式下，过滤可能的探测包
    local is_udp = ctx_is_udp(ctx)
    if is_udp and #buf < 2000 and find(buf, "HTTP/", 1, true) == 1 then
        ctx_debug("UDP masquerade: received HTTP response")
    end
    
    return DIRECT, buf
end

function wa_lua_on_write_cb(ctx, buf)
    return DIRECT, buf
end

function wa_lua_on_close_cb(ctx)
    local uuid = ctx_uuid(ctx)
    flags[uuid] = nil
    ctx_free(ctx)
    return SUCCESS
end