package cloud

import (
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"math"
	"net/http"
	"sort"
	"strconv"
	"strings"
	"time"
)

// FetchDailyBill 通过 Cost Explorer 拉取 AWS 单日服务和区域费用。 // Logan.Li
func (p *AWSProvider) FetchDailyBill(billingDate string) ([]CloudBillingRecord, error) {
	start, err := time.Parse("2006-01-02", billingDate)
	if err != nil {
		return nil, fmt.Errorf("账单日期格式应为 YYYY-MM-DD")
	}
	type aggregationKey struct {
		service string
		region  string
	}
	aggregation := map[aggregationKey]float64{}
	nextToken := ""
	currency := "USD"
	for {
		payload := map[string]interface{}{
			"TimePeriod":  map[string]string{"Start": billingDate, "End": start.AddDate(0, 0, 1).Format("2006-01-02")},
			"Granularity": "DAILY",
			"Metrics":     []string{"UnblendedCost"},
			"GroupBy": []map[string]string{
				{"Type": "DIMENSION", "Key": "SERVICE"},
				{"Type": "DIMENSION", "Key": "REGION"},
			},
		}
		if nextToken != "" {
			payload["NextPageToken"] = nextToken
		}
		body, callErr := p.callCostExplorer(payload)
		if callErr != nil {
			return nil, callErr
		}
		var response struct {
			NextPageToken string `json:"NextPageToken"`
			ResultsByTime []struct {
				Groups []struct {
					Keys    []string `json:"Keys"`
					Metrics map[string]struct {
						Amount string `json:"Amount"`
						Unit   string `json:"Unit"`
					} `json:"Metrics"`
				} `json:"Groups"`
			} `json:"ResultsByTime"`
		}
		if err = json.Unmarshal(body, &response); err != nil {
			return nil, fmt.Errorf("解析 AWS Cost Explorer 响应失败: %w", err)
		}
		for _, period := range response.ResultsByTime {
			for _, group := range period.Groups {
				metric := group.Metrics["UnblendedCost"]
				cost, _ := strconv.ParseFloat(metric.Amount, 64)
				if cost == 0 {
					continue
				}
				if metric.Unit != "" {
					currency = metric.Unit
				}
				service, region := "其他", "全局"
				if len(group.Keys) > 0 && group.Keys[0] != "" {
					service = group.Keys[0]
				}
				if len(group.Keys) > 1 && group.Keys[1] != "" && group.Keys[1] != "NoRegion" {
					region = group.Keys[1]
				}
				aggregation[aggregationKey{service: service, region: region}] += cost
			}
		}
		nextToken = response.NextPageToken
		if nextToken == "" {
			break
		}
	}
	keys := make([]aggregationKey, 0, len(aggregation))
	for key := range aggregation {
		keys = append(keys, key)
	}
	sort.Slice(keys, func(i, j int) bool {
		if keys[i].service == keys[j].service {
			return keys[i].region < keys[j].region
		}
		return keys[i].service < keys[j].service
	})
	records := make([]CloudBillingRecord, 0, len(keys))
	for _, key := range keys {
		records = append(records, CloudBillingRecord{
			BillingDate: billingDate, Provider: "aws", Cost: math.Round(aggregation[key]*1000000) / 1000000,
			Currency: currency, Service: key.service, Region: key.region,
			Description: "云 API 自动同步（AWS Cost Explorer）",
		})
	}
	return records, nil
}

// callCostExplorer 使用 Signature V4 调用 AWS Cost Explorer JSON API。 // Logan.Li
func (p *AWSProvider) callCostExplorer(payload interface{}) ([]byte, error) {
	body, err := json.Marshal(payload)
	if err != nil {
		return nil, fmt.Errorf("编码 AWS 账单请求失败: %w", err)
	}
	const host = "ce.us-east-1.amazonaws.com"
	const target = "AWSInsightsIndexService.GetCostAndUsage"
	now := time.Now().UTC()
	amzDate, date := now.Format("20060102T150405Z"), now.Format("20060102")
	canonicalHeaders := "content-type:application/x-amz-json-1.1\nhost:" + host + "\nx-amz-date:" + amzDate + "\nx-amz-target:" + target + "\n"
	signedHeaders := "content-type;host;x-amz-date;x-amz-target"
	canonicalRequest := "POST\n/\n\n" + canonicalHeaders + "\n" + signedHeaders + "\n" + sha256Hex(string(body))
	credentialScope := date + "/us-east-1/ce/aws4_request"
	stringToSign := "AWS4-HMAC-SHA256\n" + amzDate + "\n" + credentialScope + "\n" + sha256Hex(canonicalRequest)
	kDate := hmacSHA256([]byte("AWS4"+p.secretKey), date)
	kRegion := hmacSHA256(kDate, "us-east-1")
	kService := hmacSHA256(kRegion, "ce")
	signature := hex.EncodeToString(hmacSHA256(hmacSHA256(kService, "aws4_request"), stringToSign))
	req, err := http.NewRequest(http.MethodPost, "https://"+host+"/", strings.NewReader(string(body)))
	if err != nil {
		return nil, fmt.Errorf("创建 AWS 账单请求失败: %w", err)
	}
	req.Header.Set("Content-Type", "application/x-amz-json-1.1")
	req.Header.Set("X-Amz-Date", amzDate)
	req.Header.Set("X-Amz-Target", target)
	req.Header.Set("Authorization", "AWS4-HMAC-SHA256 Credential="+p.accessKey+"/"+credentialScope+", SignedHeaders="+signedHeaders+", Signature="+signature)
	resp, err := (&http.Client{Timeout: 30 * time.Second}).Do(req)
	if err != nil {
		return nil, fmt.Errorf("请求 AWS Cost Explorer 失败: %w", err)
	}
	defer resp.Body.Close()
	data, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("读取 AWS Cost Explorer 响应失败: %w", err)
	}
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return nil, fmt.Errorf("AWS Cost Explorer 返回 HTTP %d: %s", resp.StatusCode, string(data))
	}
	return data, nil
}