package domain

import (
	"fmt"

	"github.com/matcornic/hermes/v2"
)

// BuildHermesHTML renders a hermes email skeleton (same stack as stand-alone notification).
func BuildHermesHTML(brand Brand, body hermes.Body) (string, error) {
	if brand.Name == "" {
		brand.Name = "Harbor Desk"
	}
	h := hermes.Hermes{
		Product: hermes.Product{
			Name:      brand.Name,
			Link:      brand.Link,
			Logo:      brand.LogoURL,
			Copyright: brand.Copyright,
		},
		// Default theme is clean table layout suitable for most clients.
	}
	return h.GenerateHTML(hermes.Email{Body: body})
}

// GenerateTemplate builds subject + HTML for a kind/lang with placeholders still present
// ({{.Username}}, {{.VerifyCode}}, {{.ResetURL}} filled later by text/template).
func GenerateTemplate(kind TemplateKind, lang Language, brand Brand) (*EmailTemplate, error) {
	lang = NormalizeLanguage(string(lang))
	switch kind {
	case TemplateEmailVerify:
		return generateEmailVerify(lang, brand)
	case TemplatePasswordReset:
		return generatePasswordReset(lang, brand)
	default:
		return nil, fmt.Errorf("unknown template kind: %s", kind)
	}
}

func generateEmailVerify(lang Language, brand Brand) (*EmailTemplate, error) {
	var subject string
	var intros, outros []string
	var instr string
	if lang == LangEnUS {
		subject = "[Harbor Desk] Verify your email"
		intros = []string{
			"You received this email because we need to verify your email address.",
		}
		instr = "Copy this verification code and enter it on the verify page (valid for 30 minutes):"
		outros = []string{
			"If you did not create an account, you can ignore this email.",
			"This is an automated message — please do not reply.",
		}
	} else {
		subject = "【Harbor Desk】信箱驗證碼"
		intros = []string{
			"您收到此信是因為需要驗證您的電子信箱。",
		}
		instr = "請複製下方驗證碼，於 30 分鐘內到驗證頁完成確認："
		outros = []string{
			"若您並未註冊帳號，可忽略本信。",
			"此為系統自動發出，請勿直接回覆。",
		}
	}
	html, err := BuildHermesHTML(brand, hermes.Body{
		Name:   "{{.Username}}",
		Intros: intros,
		Actions: []hermes.Action{
			{
				Instructions: instr,
				InviteCode:   "{{.VerifyCode}}",
			},
		},
		Outros:    outros,
		Signature: " ",
	})
	if err != nil {
		return nil, err
	}
	return &EmailTemplate{Subject: subject, Body: html}, nil
}

func generatePasswordReset(lang Language, brand Brand) (*EmailTemplate, error) {
	var subject, instr, btnText string
	var intros, outros []string
	if lang == LangEnUS {
		subject = "[Harbor Desk] Reset your password"
		intros = []string{
			"You received this email because a password reset was requested for your account.",
		}
		instr = "Copy this code, or open the reset page with the button below (valid for 30 minutes):"
		btnText = "Open reset page"
		outros = []string{
			"If you did not request a password reset, no further action is required.",
			"This is an automated message — please do not reply.",
		}
	} else {
		subject = "【Harbor Desk】重設密碼"
		intros = []string{
			"您收到此信是因為有人申請重設您的帳戶密碼。",
		}
		instr = "請複製下方驗證碼，或點擊按鈕開啟重設頁（30 分鐘內有效）："
		btnText = "開啟重設密碼頁"
		outros = []string{
			"若您並未申請重設密碼，可忽略本信，帳號不會有任何變更。",
			"此為系統自動發出，請勿直接回覆。",
		}
	}

	actions := []hermes.Action{
		{
			Instructions: instr,
			InviteCode:   "{{.VerifyCode}}",
		},
	}
	// Button only when ResetURL placeholder present after render — always include;
	// empty href is avoided by filling ResetURL before send.
	actions = append(actions, hermes.Action{
		Button: hermes.Button{
			Color: "#0f172a",
			Text:  btnText,
			Link:  "{{.ResetURL}}",
		},
	})

	html, err := BuildHermesHTML(brand, hermes.Body{
		Name:      "{{.Username}}",
		Intros:    intros,
		Actions:   actions,
		Outros:    outros,
		Signature: " ",
	})
	if err != nil {
		return nil, err
	}
	return &EmailTemplate{Subject: subject, Body: html}, nil
}