package emailtemplates

import (
	"Yimaru-Backend/internal/domain"
	"bytes"
)

var defaultTemplates = map[string]domain.EmailTemplate{
	domain.EmailTemplateSlugOTP: {
		Slug:     domain.EmailTemplateSlugOTP,
		Name:     "One-Time Password",
		Subject:  "Yimaru - One Time Password",
		BodyText: "Welcome to Yimaru Online Learning Platform{{if .FirstName}}, {{.FirstName}}{{end}}. Your OTP is {{.OTP}}. It expires in {{.ExpiresMinutes}} minutes. Please do not share it with anyone.",
		BodyHTML: "<p>Welcome to Yimaru Online Learning Platform{{if .FirstName}}, <strong>{{.FirstName}}</strong>{{end}}.</p><p>Your one-time password is <strong>{{.OTP}}</strong>.</p><p>It expires in {{.ExpiresMinutes}} minutes. Please do not share it with anyone.</p>",
		Variables: []string{"OTP", "FirstName", "ExpiresMinutes"},
		Status:   domain.EmailTemplateStatusActive,
	},
	domain.EmailTemplateSlugInvitation: {
		Slug:     domain.EmailTemplateSlugInvitation,
		Name:     "User Invitation",
		Subject:  "You are invited to join Yimaru",
		BodyText: "Hi{{if .FirstName}} {{.FirstName}}{{end}}, you have been invited{{if .InviterName}} by {{.InviterName}}{{end}} to join Yimaru Online Learning Platform. Accept your invitation: {{.InviteLink}}",
		BodyHTML: "<p>Hi{{if .FirstName}} <strong>{{.FirstName}}</strong>{{end}},</p><p>You have been invited{{if .InviterName}} by <strong>{{.InviterName}}</strong>{{end}} to join Yimaru Online Learning Platform.</p><p><a href=\"{{.InviteLink}}\">Accept your invitation</a></p>",
		Variables: []string{"FirstName", "InviterName", "InviteLink"},
		Status:   domain.EmailTemplateStatusActive,
	},
	domain.EmailTemplateSlugPasswordReset: {
		Slug:     domain.EmailTemplateSlugPasswordReset,
		Name:     "Password Reset",
		Subject:  "Reset your Yimaru password",
		BodyText: "Hi{{if .FirstName}} {{.FirstName}}{{end}}, use this link to reset your password: {{.ResetLink}}. The link expires in {{.ExpiresMinutes}} minutes.",
		BodyHTML: "<p>Hi{{if .FirstName}} <strong>{{.FirstName}}</strong>{{end}},</p><p>Use the link below to reset your password. It expires in {{.ExpiresMinutes}} minutes.</p><p><a href=\"{{.ResetLink}}\">Reset your password</a></p>",
		Variables: []string{"FirstName", "ResetLink", "ExpiresMinutes"},
		Status:   domain.EmailTemplateStatusActive,
	},
	domain.EmailTemplateSlugWelcome: {
		Slug:     domain.EmailTemplateSlugWelcome,
		Name:     "Welcome Email",
		Subject:  "Welcome to Yimaru",
		BodyText: "Hi{{if .FirstName}} {{.FirstName}}{{end}}, welcome to Yimaru Online Learning Platform! Sign in at {{.LoginURL}} to get started.",
		BodyHTML: "<p>Hi{{if .FirstName}} <strong>{{.FirstName}}</strong>{{end}},</p><p>Welcome to Yimaru Online Learning Platform!</p><p><a href=\"{{.LoginURL}}\">Sign in to get started</a></p>",
		Variables: []string{"FirstName", "LoginURL"},
		Status:   domain.EmailTemplateStatusActive,
	},
	domain.EmailTemplateSlugCustomMessage: {
		Slug:     domain.EmailTemplateSlugCustomMessage,
		Name:     "Custom Message",
		Subject:  "{{.Subject}}",
		BodyText: "{{.Message}}",
		BodyHTML: "<p>{{.Message}}</p>",
		Variables: []string{"Subject", "Message"},
		Status:   domain.EmailTemplateStatusActive,
	},
}

func defaultTemplate(slug string) (domain.EmailTemplate, bool) {
	tmpl, ok := defaultTemplates[slug]
	return tmpl, ok
}

func renderTemplateFields(tmpl domain.EmailTemplate, data map[string]any) (domain.RenderedEmail, error) {
	if data == nil {
		data = map[string]any{}
	}

	subject, err := executeTextTemplate("subject:"+tmpl.Slug, tmpl.Subject, data)
	if err != nil {
		return domain.RenderedEmail{}, err
	}

	text, err := executeTextTemplate("text:"+tmpl.Slug, tmpl.BodyText, data)
	if err != nil {
		return domain.RenderedEmail{}, err
	}

	html, err := executeHTMLTemplate("html:"+tmpl.Slug, tmpl.BodyHTML, data)
	if err != nil {
		return domain.RenderedEmail{}, err
	}

	return domain.RenderedEmail{
		Subject: subject,
		Text:    text,
		HTML:    html,
	}, nil
}

func executeTextTemplate(name, content string, data map[string]any) (string, error) {
	tmpl, err := newTextTemplate(name, content)
	if err != nil {
		return "", err
	}

	var buf bytes.Buffer
	if err := tmpl.Execute(&buf, data); err != nil {
		return "", err
	}
	return buf.String(), nil
}

func executeHTMLTemplate(name, content string, data map[string]any) (string, error) {
	tmpl, err := newHTMLTemplate(name, content)
	if err != nil {
		return "", err
	}

	var buf bytes.Buffer
	if err := tmpl.Execute(&buf, data); err != nil {
		return "", err
	}
	return buf.String(), nil
}