-- =========================================
-- 文件上传接口
-- =========================================
local upload = require "resty.upload"
local cjson = require "cjson.safe"

ngx.header.content_type = "application/json; charset=utf-8"

local upload_dir = "/opt/oss/upload/"
local max_size = 20 * 1024 * 1024  -- 20MB

-- 工具函数
local function now_ms()
    return tostring(math.floor(ngx.now() * 1000))
end

local function get_ym()
    return os.date("%Y%m")
end

local function safe_suffix(name)
    -- 获取文件后缀，例如 .png
    return name:match("^.+(%..+)$") or ""
end

local form, err = upload:new(4096)
if not form then
    ngx.say(cjson.encode({ code = 500, msg = "创建上传对象失败: " .. (err or ""), data = {} }))
    return
end
form:set_timeout(10000)

local file, filename, filesize = nil, nil, 0

while true do
    local typ, res, err = form:read()
    if not typ then
        ngx.say(cjson.encode({ code = 500, msg = "读取上传内容失败: " .. (err or ""), data = {} }))
        return
    end

    if typ == "header" then
        local name, value = res[1], res[2]
        if name == "Content-Disposition" then
            local orig_name = value:match('filename="(.-)"')
            if orig_name then
                local suffix = safe_suffix(orig_name)
                local newname = get_ym() .. "_" .. now_ms() .. suffix
                local fullpath = upload_dir .. newname

                -- 判断文件是否存在
                local f = io.open(fullpath, "r")
                if f then
                    f:close()
                    ngx.say(cjson.encode({code = 429, msg = "当前访问人数较多，请稍后重试", data = {}}))
                    return
                end

                -- 打开文件写入
                file, err = io.open(fullpath, "w+")
                if not file then
                    ngx.say(cjson.encode({ code = 500, msg = "无法创建文件: " .. (err or ""), data = {} }))
                    return
                end

                filename = newname
            end
        end
    elseif typ == "body" then
        if file then
            filesize = filesize + #res
            if filesize > max_size then
                file:close()
                os.remove(upload_dir .. filename)
                ngx.say(cjson.encode({ code = 413, msg = "文件过大（限制20MB）", data = {} }))
                return
            end
            file:write(res)
        end
    elseif typ == "part_end" then
        if file then
            file:close()
            file = nil
        end
    elseif typ == "eof" then
        break
    end
end

ngx.say(cjson.encode({
    code = 200,
    msg = "上传成功",
    data = {
        filename = filename,
        url = "/oss/upload/" .. filename,
        size = filesize
    }
}))