package service

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

	"gorm.io/gorm"
)

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

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 := renderNginxConfig(routes)
	version, err := nextVersionNumber(time.Now())
	if err != nil {
		return nil, err
	}
	record := &model.ConfigVersion{
		Version:        version,
		SnapshotJSON:   snapshotJSON,
		RenderedConfig: renderedConfig,
		Checksum:       checksum(renderedConfig),
		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"`
		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,
			Remark:    route.Remark,
		})
	}
	data, err := json.Marshal(items)
	if err != nil {
		return "", err
	}
	return string(data), nil
}

func renderNginxConfig(routes []*model.ProxyRoute) string {
	var builder strings.Builder
	builder.WriteString("# This file is generated by ATSFlare. Do not edit manually.\n")
	for _, route := range routes {
		builder.WriteString(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", route.Domain, route.OriginURL))
	}
	return builder.String()
}

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

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
}