local strip_path = require("strip_path")

-- filename eg. /file_upload/xxxx-xxxx-xxxx-xxxx.mp3
local function calc_token(filename)

    -- Upyun upload parameters
    local operator = ngx.var.upyun_operator
    local password = ngx.var.upyun_password
    local bucket = ngx.var.upyun_bucket
    local directory = ngx.var.upyun_directory

    local expiration = 1800
    local method = "POST"

    local save_key = "/" .. directory .. "/" .. strip_path.strip_path(filename)
    print("save key...", save_key)
    -- Get RFC1123 data
    local date = ngx.http_time(ngx.time()) -- RFC1123 date
    print("date ...", date)
    -- Generate upyun UCT time
    local utc_time = os.time(os.date("!*t"))
    -- Calculate upyun file expiration
    expiration = utc_time + expiration
    print("expiration ...", expiration)
    -- 不能使用cjson，因为lua的table没有顺序，cjson encode出来的顺序会错乱
    local policy = string.format("{\"bucket\":\"%s\",\"save-key\":\"%s\",\"expiration\":\"%s\",\"date\":\"%s\"}", bucket, save_key, expiration, date)
    local to_be_signed = method .. "&" .. "/" .. bucket .. "&" .. date .. "&" .. ngx.encode_base64(policy)
    print("to be signed ...", to_be_signed)
    local hmac_sha1 = ngx.hmac_sha1(ngx.md5(password), to_be_signed)
    local signature = ngx.encode_base64(hmac_sha1)

    return { token = string.format("UPYUN %s:%s", operator, signature), policy = policy }
end


return calc_token