/*
Copyright 2026 Arctel.net

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package model

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"strings"
	"text/template"
	"time"

	"github.com/Rain-kl/Wavelet/internal/db"
)

type Template struct {
	ID          uint64    `json:"id" gorm:"primaryKey;autoIncrement"`
	Key         string    `json:"key" gorm:"uniqueIndex;size:80;not null"`
	Name        string    `json:"name" gorm:"size:100;not null"`
	Type        string    `json:"type" gorm:"size:20;not null;default:'email'"`
	Subject     string    `json:"subject" gorm:"size:255"`
	Content     string    `json:"content" gorm:"type:text;not null"`
	Description string    `json:"description" gorm:"size:255"`
	IsSystem    bool      `json:"is_system" gorm:"index;not null;default:false"`
	CreatedAt   time.Time `json:"created_at" gorm:"autoCreateTime;index"`
	UpdatedAt   time.Time `json:"updated_at" gorm:"autoUpdateTime;index"`
}

func (t *Template) Normalize() {
	t.Key = strings.TrimSpace(t.Key)
	t.Name = strings.TrimSpace(t.Name)
	t.Type = strings.ToLower(strings.TrimSpace(t.Type))
	t.Subject = strings.TrimSpace(t.Subject)
	t.Content = strings.TrimSpace(t.Content)
	t.Description = strings.TrimSpace(t.Description)
	if t.Type == "" {
		t.Type = "email"
	}
}

func (t *Template) Validate() error {
	t.Normalize()
	if t.Key == "" {
		return errors.New(errTemplateKeyRequired)
	}
	if t.Name == "" {
		return errors.New(errTemplateNameRequired)
	}
	if t.Content == "" {
		return errors.New(errTemplateContentRequired)
	}
	return nil
}

func (t *Template) Render(data any) (string, string, error) {
	// Render Subject
	var subject string
	if t.Subject != "" {
		tmplSubject, err := template.New(t.Key + "_subject").Parse(t.Subject)
		if err != nil {
			return "", "", err
		}
		var subBuf bytes.Buffer
		if err := tmplSubject.Execute(&subBuf, data); err != nil {
			return "", "", err
		}
		subject = subBuf.String()
	}

	// Render Content
	tmplContent, err := template.New(t.Key + "_content").Parse(t.Content)
	if err != nil {
		return "", "", err
	}
	var bodyBuf bytes.Buffer
	if err := tmplContent.Execute(&bodyBuf, data); err != nil {
		return "", "", err
	}

	return subject, bodyBuf.String(), nil
}

// RenderTemplate 渲染指定模板。模板不存在或渲染失败时返回错误，由调用方决定如何处理。
func RenderTemplate(ctx context.Context, key string, data any) (string, string, error) {
	var t Template
	if err := db.DB(ctx).Where("key = ?", key).First(&t).Error; err != nil {
		return "", "", fmt.Errorf(errTemplateUnavailable, key, err)
	}

	subject, body, err := t.Render(data)
	if err != nil {
		return "", "", fmt.Errorf(errTemplateRenderFailed, key, err)
	}
	return subject, body, nil
}