package upload

import (
	"bytes"
	"crypto/hmac"
	"crypto/sha1"
	"joybuywork/internal/config"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"github.com/rs/xid"
	"hash"
	"io"
	"time"
)

type ConfigStruct struct {
	Expiration string     `json:"expiration"`
	Conditions [][]string `json:"conditions"`
}

type PolicyToken struct {
	Expire    int64
	Signature string
	Policy    string
	Directory string
	Key       string
}

// GetPolicy 获取上传token
func GetPolicy(fileSuffix string) (policyToken PolicyToken) {
	var (
		exp      = time.Now().Add(30 * time.Second)
		expDate  = exp.Format("2006-01-02T15:04:05Z")
		secret   = bytes.NewBufferString(config.Config.Upload.Secret)
		dir      = fmt.Sprintf("%s%s/", config.Config.Upload.Prefix, time.Now().Format("2006/01/02"))
		filename = xid.New().String()
	)

	if fileSuffix != "" {
		filename = fmt.Sprintf("%s.%s", filename, fileSuffix)
	}

	//create post policy json
	var conf ConfigStruct
	conf.Expiration = expDate
	var condition []string
	condition = append(condition, "starts-with")
	condition = append(condition, "$key")
	condition = append(condition, dir)
	conf.Conditions = append(conf.Conditions, condition)

	//calucate signature
	result, _ := json.Marshal(conf)
	debyte := base64.StdEncoding.EncodeToString(result)
	h := hmac.New(func() hash.Hash { return sha1.New() }, secret.Bytes())
	io.WriteString(h, debyte)
	signedStr := base64.StdEncoding.EncodeToString(h.Sum(nil))

	policyToken.Expire = int64(exp.Sub(time.Now()).Seconds())
	policyToken.Signature = signedStr
	policyToken.Directory = dir
	policyToken.Policy = debyte
	policyToken.Key = filename

	return
}