package service

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"gin-template/model"
	"sort"
	"strings"
	"time"

	"gorm.io/gorm"
)

type ReleaseResult struct {
	Version *model.ConfigVersion `json:"version"`
	Routes  []*model.ProxyRoute  `json:"routes"`
}

type SupportFile struct {
	Path    string `json:"path"`
	Content string `json:"content"`
}

const nginxCertDirPlaceholder = "__ATSF_CERT_DIR__"

func ListConfigVersions() ([]*model.ConfigVersion, error) {
	return model.ListConfigVersions()
}

func GetActiveConfigVersion() (*model.ConfigVersion, error) {
	return model.GetActiveConfigVersion()
}

func PublishConfigVersion(createdBy string) (*ReleaseResult, error) {
	routes, err := model.GetEnabledProxyRoutes()
	if err != nil {
		return nil, err
	}
	if len(routes) == 0 {
		return nil, errors.New("没有可发布的启用规则")
	}
	snapshotJSON, err := renderSnapshot(routes)
	if err != nil {
		return nil, err
	}
	renderedConfig, supportFiles, err := renderNginxConfig(routes)
	if err != nil {
		return nil, err
	}
	supportFilesJSON, err := json.Marshal(supportFiles)
	if err != nil {
		return nil, err
	}
	version, err := nextVersionNumber(time.Now())
	if err != nil {
		return nil, err
	}
	record := &model.ConfigVersion{
		Version:          version,
		SnapshotJSON:     snapshotJSON,
		RenderedConfig:   renderedConfig,
		SupportFilesJSON: string(supportFilesJSON),
		Checksum:         checksumBundle(renderedConfig, supportFiles),
		IsActive:         true,
		CreatedBy:        createdBy,
	}
	err = model.DB.Transaction(func(tx *gorm.DB) error {
		if err := tx.Model(&model.ConfigVersion{}).Where("is_active = ?", true).Update("is_active", false).Error; err != nil {
			return err
		}
		if err := tx.Create(record).Error; err != nil {
			return err
		}
		return nil
	})
	if err != nil {
		if isUniqueConstraintError(err) {
			return nil, errors.New("版本号生成冲突，请重试")
		}
		return nil, err
	}
	return &ReleaseResult{
		Version: record,
		Routes:  routes,
	}, nil
}

func ActivateConfigVersion(id uint) (*model.ConfigVersion, error) {
	version, err := model.GetConfigVersionByID(id)
	if err != nil {
		return nil, err
	}
	err = model.DB.Transaction(func(tx *gorm.DB) error {
		if err := tx.Model(&model.ConfigVersion{}).Where("is_active = ?", true).Update("is_active", false).Error; err != nil {
			return err
		}
		if err := tx.Model(version).Update("is_active", true).Error; err != nil {
			return err
		}
		return nil
	})
	if err != nil {
		return nil, err
	}
	version.IsActive = true
	return version, nil
}

func renderSnapshot(routes []*model.ProxyRoute) (string, error) {
	type snapshotRoute struct {
		Domain       string `json:"domain"`
		OriginURL    string `json:"origin_url"`
		Enabled      bool   `json:"enabled"`
		EnableHTTPS  bool   `json:"enable_https"`
		CertID       *uint  `json:"cert_id,omitempty"`
		RedirectHTTP bool   `json:"redirect_http"`
		Remark       string `json:"remark,omitempty"`
	}
	items := make([]snapshotRoute, 0, len(routes))
	for _, route := range routes {
		items = append(items, snapshotRoute{
			Domain:    route.Domain,
			OriginURL: route.OriginURL,
			Enabled:   route.Enabled,
			EnableHTTPS: route.EnableHTTPS,
			CertID: route.CertID,
			RedirectHTTP: route.RedirectHTTP,
			Remark:    route.Remark,
		})
	}
	data, err := json.Marshal(items)
	if err != nil {
		return "", err
	}
	return string(data), nil
}

func renderNginxConfig(routes []*model.ProxyRoute) (string, []SupportFile, error) {
	var builder strings.Builder
	builder.WriteString("# This file is generated by ATSFlare. Do not edit manually.\n")
	supportFiles := make([]SupportFile, 0)
	for _, route := range routes {
		if !route.EnableHTTPS {
			builder.WriteString(renderHTTPProxyServer(route.Domain, route.OriginURL))
			continue
		}
		if route.CertID == nil || *route.CertID == 0 {
			return "", nil, fmt.Errorf("路由 %s 未配置证书", route.Domain)
		}
		certificate, err := model.GetTLSCertificateByID(*route.CertID)
		if err != nil {
			return "", nil, fmt.Errorf("路由 %s 关联证书不存在", route.Domain)
		}
		supportFiles = append(supportFiles,
			SupportFile{Path: certificateCertFileName(certificate.ID), Content: normalizePEM(certificate.CertPEM)},
			SupportFile{Path: certificateKeyFileName(certificate.ID), Content: normalizePEM(certificate.KeyPEM)},
		)
		if route.RedirectHTTP {
			builder.WriteString(renderHTTPRedirectServer(route.Domain))
		} else {
			builder.WriteString(renderHTTPProxyServer(route.Domain, route.OriginURL))
		}
		builder.WriteString(renderHTTPSServer(route.Domain, route.OriginURL, certificate.ID))
	}
	return builder.String(), dedupeSupportFiles(supportFiles), nil
}

func checksum(content string) string {
	sum := sha256.Sum256([]byte(content))
	return hex.EncodeToString(sum[:])
}

func checksumBundle(renderedConfig string, supportFiles []SupportFile) string {
	var builder strings.Builder
	builder.WriteString(renderedConfig)
	builder.WriteString("\n--support-files--\n")
	files := dedupeSupportFiles(supportFiles)
	sort.Slice(files, func(i int, j int) bool {
		return files[i].Path < files[j].Path
	})
	for _, file := range files {
		builder.WriteString(file.Path)
		builder.WriteString("\n")
		builder.WriteString(file.Content)
		builder.WriteString("\n")
	}
	return checksum(builder.String())
}

func nextVersionNumber(now time.Time) (string, error) {
	prefix := now.Format("20060102")
	var count int64
	if err := model.DB.Model(&model.ConfigVersion{}).Where("version LIKE ?", prefix+"-%").Count(&count).Error; err != nil {
		return "", err
	}
	return fmt.Sprintf("%s-%03d", prefix, count+1), nil
}

func renderHTTPProxyServer(domain string, originURL string) string {
	return fmt.Sprintf("server {\n    listen 80;\n    server_name %s;\n\n    location / {\n        proxy_set_header Host $host;\n        proxy_set_header X-Real-IP $remote_addr;\n        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;\n        proxy_set_header X-Forwarded-Proto $scheme;\n        proxy_pass %s;\n    }\n}\n\n", domain, originURL)
}

func renderHTTPRedirectServer(domain string) string {
	return fmt.Sprintf("server {\n    listen 80;\n    server_name %s;\n\n    return 301 https://$host$request_uri;\n}\n\n", domain)
}

func renderHTTPSServer(domain string, originURL string, certificateID uint) string {
	certPath := fmt.Sprintf("%s/%s", nginxCertDirPlaceholder, certificateCertFileName(certificateID))
	keyPath := fmt.Sprintf("%s/%s", nginxCertDirPlaceholder, certificateKeyFileName(certificateID))
	return fmt.Sprintf("server {\n    listen 443 ssl;\n    server_name %s;\n    ssl_certificate %s;\n    ssl_certificate_key %s;\n\n    location / {\n        proxy_set_header Host $host;\n        proxy_set_header X-Real-IP $remote_addr;\n        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;\n        proxy_set_header X-Forwarded-Proto $scheme;\n        proxy_pass %s;\n    }\n}\n\n", domain, certPath, keyPath, originURL)
}

func certificateCertFileName(id uint) string {
	return fmt.Sprintf("%d.crt", id)
}

func certificateKeyFileName(id uint) string {
	return fmt.Sprintf("%d.key", id)
}

func normalizePEM(content string) string {
	return strings.TrimSpace(content) + "\n"
}

func dedupeSupportFiles(files []SupportFile) []SupportFile {
	if len(files) == 0 {
		return nil
	}
	unique := make(map[string]SupportFile, len(files))
	for _, file := range files {
		unique[file.Path] = file
	}
	result := make([]SupportFile, 0, len(unique))
	for _, file := range unique {
		result = append(result, file)
	}
	return result
}