package mailer

import (
	"bytes"
	"embed"
	"fmt"
	htmltemplate "html/template"
	texttemplate "text/template"
)

//go:embed templates/password_reset.txt templates/password_reset.html
var resetEmailFS embed.FS

// ResetEmailVars is the data passed to the password reset templates.
type ResetEmailVars struct {
	Username    string
	ResetURL    string
	ExpiryHours int
}

// RenderResetEmail returns (textBody, htmlBody) for the password
// reset email, parameterized with the given vars.
func RenderResetEmail(vars ResetEmailVars) (string, string, error) {
	textTpl, err := texttemplate.ParseFS(resetEmailFS, "templates/password_reset.txt")
	if err != nil {
		return "", "", fmt.Errorf("mailer: parse text template: %w", err)
	}
	htmlTpl, err := htmltemplate.ParseFS(resetEmailFS, "templates/password_reset.html")
	if err != nil {
		return "", "", fmt.Errorf("mailer: parse html template: %w", err)
	}

	var textBuf, htmlBuf bytes.Buffer
	if err := textTpl.Execute(&textBuf, vars); err != nil {
		return "", "", fmt.Errorf("mailer: render text: %w", err)
	}
	if err := htmlTpl.Execute(&htmlBuf, vars); err != nil {
		return "", "", fmt.Errorf("mailer: render html: %w", err)
	}
	return textBuf.String(), htmlBuf.String(), nil
}

// ResetEmailSubject is the subject line used by the forgot-password
// flow. Exported so callers don't string-literal it independently.
const ResetEmailSubject = "Minstrel password reset"