package fileauth

import (
	"encoding/base64"
	"encoding/json"
	"errors"
	"strings"
)

// UploadTokenParts 上传凭证分步结果（FileAuth.java：AccessKey:encodedSign:policyB64）。
type UploadTokenParts struct {
	AccessKey        string
	PolicyJSON       string
	EncodedPutPolicy string // 第三段：policy JSON 的 URL-safe Base64
	SignInput        string // HMAC 输入：policy JSON 明文
	EncodedSign      string
	UploadToken      string
	DeadlineUnix     int64
	ExpiresSec       int64
	Algorithm        string
}

// FormatCheck 单条 uploadToken 格式校验结果。
type FormatCheck struct {
	ID     string `json:"id"`
	OK     bool   `json:"ok"`
	Detail string `json:"detail"`
}

// BuildUploadTokenParts 分步生成上传凭证（生产 upload profile，scope=仅 bucket）。
func BuildUploadTokenParts(accessKey, secret, bucket string, deadlineUnix int64) (UploadTokenParts, error) {
	return BuildUploadTokenPartsForUpload(accessKey, secret, bucket, deadlineUnix)
}

// SplitUploadToken 按前两处英文冒号拆分为 accessKey、encodedSign、encodedPutPolicy。
func SplitUploadToken(token string) (accessKey, encodedSign, encodedPutPolicy string, ok bool) {
	token = strings.TrimSpace(token)
	i := strings.Index(token, ":")
	if i <= 0 {
		return "", "", "", false
	}
	rest := token[i+1:]
	j := strings.Index(rest, ":")
	if j <= 0 {
		return "", "", "", false
	}
	ak := token[:i]
	sign := rest[:j]
	pol := rest[j+1:]
	if ak == "" || sign == "" || pol == "" {
		return "", "", "", false
	}
	return ak, sign, pol, true
}

// ValidateUploadTokenFormat 校验 token 是否符合 AccessKey:sign:policyB64；expectedAccessKey 非空时校验首段。
func ValidateUploadTokenFormat(token, expectedAccessKey string) (allOK bool, checks []FormatCheck) {
	ak, sign, pol, ok := SplitUploadToken(token)
	checks = []FormatCheck{
		{
			ID:     "three_parts",
			OK:     ok,
			Detail: "uploadToken = AccessKey + ':' + encodedSign + ':' + policyB64（按前两处冒号拆分）",
		},
		{
			ID:     "access_key_non_empty",
			OK:     ok && ak != "",
			Detail: "第 1 段 AccessKey 非空",
		},
		{
			ID:     "encoded_sign_non_empty",
			OK:     ok && sign != "",
			Detail: "第 2 段 encodedSign（URL-safe Base64 HMAC）非空",
		},
		{
			ID:     "encoded_policy_non_empty",
			OK:     ok && pol != "",
			Detail: "第 3 段 policyB64（URL-safe Base64 policy JSON）非空",
		},
	}
	if expectedAccessKey != "" {
		exp := strings.TrimSpace(expectedAccessKey)
		match := ok && ak == exp
		checks = append(checks, FormatCheck{
			ID:     "access_key_match",
			OK:     match,
			Detail: "第 1 段与当前 AccessKey 一致",
		})
	}
	_, decErr := DecodePutPolicyB64(pol)
	checks = append(checks, FormatCheck{
		ID:     "policy_b64_decodable",
		OK:     ok && decErr == nil,
		Detail: "第 3 段可 URL-safe Base64 解码为 JSON",
	})
	allOK = true
	for _, c := range checks {
		if !c.OK {
			allOK = false
			break
		}
	}
	return allOK, checks
}

// DecodePutPolicyB64 解码 policyB64 为 JSON 字符串（美化缩进）。
func DecodePutPolicyB64(encoded string) (string, error) {
	encoded = strings.TrimSpace(encoded)
	if encoded == "" {
		return "", errors.New("empty encoded policy")
	}
	raw, err := base64.RawURLEncoding.DecodeString(encoded)
	if err != nil {
		raw, err = base64.URLEncoding.DecodeString(encoded)
		if err != nil {
			return "", err
		}
	}
	var pretty interface{}
	if err := json.Unmarshal(raw, &pretty); err != nil {
		return string(raw), nil
	}
	out, err := json.MarshalIndent(pretty, "", "  ")
	if err != nil {
		return string(raw), nil
	}
	return string(out), nil
}