package policy

import (
	"errors"
	"net/mail"

	"go.starlark.net/starlark"
)

type MessageContext struct {
	HeaderFrom Address
	HeaderTo   Address
	Subject    string
	Headers    mail.Header
	Size       int64
}

func (m MessageContext) String() string { return "<MessageContext>" }
func (m MessageContext) Type() string   { return "MessageContext" }
func (m MessageContext) Freeze() {
	m.HeaderFrom.Freeze()
	m.HeaderTo.Freeze()
}
func (m MessageContext) Truth() starlark.Bool { return true }
func (m MessageContext) Hash() (uint32, error) {
	return 0, errors.New("unhashable")
}

func (m MessageContext) Attr(name string) (starlark.Value, error) {
	switch name {
	case "header_from":
		return m.HeaderFrom, nil
	case "header_to":
		return m.HeaderTo, nil
	case "subject":
		return starlark.String(m.Subject), nil
	case "size":
		return starlark.MakeInt64(m.Size), nil
	}
	return nil, nil
}

func (m MessageContext) AttrNames() []string {
	return []string{"header_from", "header_to", "subject", "size"}
}

// MessageContextFromEnvelope builds a policy.MessageContext from the envelope
// fields of a stored message. The header_from address is parsed into an
// Address; if parsing fails the raw string is preserved.
func MessageContextFromEnvelope(from, subject string, size int64) MessageContext {
	fromAddr, err := ParseAddress(from)
	if err != nil || from == "" {
		fromAddr = Address{Raw: from, Address: from}
	}
	return MessageContext{
		HeaderFrom: fromAddr,
		Subject:    subject,
		Size:       size,
	}
}