// Package publishmail encodes accepted email routes into Mail Service generic
// asynchronous template commands.
package publishmail

import (
	"encoding/json"
	"fmt"
	netmail "net/mail"
	"strconv"
	"strings"
	"time"

	"galaxy/notification/internal/api/intentstream"
	"galaxy/notification/internal/service/acceptintent"
)

const (
	commandSourceNotification  = "notification"
	commandPayloadModeTemplate = "template"
)

// Command stores one Mail Service-compatible template delivery command
// produced from a durable notification email route.
type Command struct {
	// DeliveryID stores the stable route-level delivery identifier.
	DeliveryID string

	// IdempotencyKey stores the stable Mail Service deduplication key.
	IdempotencyKey string

	// RequestedAt stores when Notification Service durably accepted the
	// notification intent.
	RequestedAt time.Time

	// PayloadJSON stores the fully encoded template-mode command payload.
	PayloadJSON string

	// RequestID stores the optional correlation identifier.
	RequestID string

	// TraceID stores the optional tracing correlation identifier.
	TraceID string
}

// Values returns the Redis Stream fields appended to the Mail Service command
// stream for Command.
func (command Command) Values() map[string]any {
	values := map[string]any{
		"delivery_id":     command.DeliveryID,
		"source":          commandSourceNotification,
		"payload_mode":    commandPayloadModeTemplate,
		"idempotency_key": command.IdempotencyKey,
		"requested_at_ms": strconv.FormatInt(command.RequestedAt.UTC().UnixMilli(), 10),
		"payload_json":    command.PayloadJSON,
	}
	if command.RequestID != "" {
		values["request_id"] = command.RequestID
	}
	if command.TraceID != "" {
		values["trace_id"] = command.TraceID
	}

	return values
}

// Encoder converts one accepted notification record plus its email route into
// one Mail Service-compatible generic template command.
type Encoder struct{}

// Encode converts notification plus route into one template delivery command.
func (Encoder) Encode(notification acceptintent.NotificationRecord, route acceptintent.NotificationRoute) (Command, error) {
	if err := notification.Validate(); err != nil {
		return Command{}, fmt.Errorf("encode mail command: %w", err)
	}
	if err := route.Validate(); err != nil {
		return Command{}, fmt.Errorf("encode mail command: %w", err)
	}
	if notification.NotificationID != route.NotificationID {
		return Command{}, fmt.Errorf("encode mail command: notification id %q does not match route notification id %q", notification.NotificationID, route.NotificationID)
	}
	if route.Channel != intentstream.ChannelEmail {
		return Command{}, fmt.Errorf("encode mail command: route channel %q is unsupported", route.Channel)
	}
	if !notification.NotificationType.SupportsChannel(notification.AudienceKind, intentstream.ChannelEmail) {
		return Command{}, fmt.Errorf("encode mail command: payload_encoding_failed: notification type %q does not support email", notification.NotificationType)
	}

	recipientEmail, err := normalizedRecipientEmail(route.ResolvedEmail)
	if err != nil {
		return Command{}, fmt.Errorf("encode mail command: payload_encoding_failed: %w", err)
	}
	locale, err := normalizedLocale(route.ResolvedLocale)
	if err != nil {
		return Command{}, fmt.Errorf("encode mail command: payload_encoding_failed: %w", err)
	}
	variables, err := payloadVariables(notification.PayloadJSON)
	if err != nil {
		return Command{}, fmt.Errorf("encode mail command: payload_encoding_failed: %w", err)
	}

	payloadJSON, err := json.Marshal(templatePayloadJSON{
		To:          []string{recipientEmail},
		Cc:          []string{},
		Bcc:         []string{},
		ReplyTo:     []string{},
		TemplateID:  string(notification.NotificationType),
		Locale:      locale,
		Variables:   variables,
		Attachments: []templateAttachmentJSON{},
	})
	if err != nil {
		return Command{}, fmt.Errorf("encode mail command: payload_encoding_failed: marshal payload_json: %w", err)
	}

	return Command{
		DeliveryID:     notification.NotificationID + "/" + route.RouteID,
		IdempotencyKey: "notification:" + notification.NotificationID + "/" + route.RouteID,
		RequestedAt:    notification.AcceptedAt,
		PayloadJSON:    string(payloadJSON),
		RequestID:      notification.RequestID,
		TraceID:        notification.TraceID,
	}, nil
}

type templatePayloadJSON struct {
	To          []string                 `json:"to"`
	Cc          []string                 `json:"cc"`
	Bcc         []string                 `json:"bcc"`
	ReplyTo     []string                 `json:"reply_to"`
	TemplateID  string                   `json:"template_id"`
	Locale      string                   `json:"locale"`
	Variables   json.RawMessage          `json:"variables"`
	Attachments []templateAttachmentJSON `json:"attachments"`
}

type templateAttachmentJSON struct {
	Filename      string `json:"filename"`
	ContentType   string `json:"content_type"`
	ContentBase64 string `json:"content_base64"`
}

func normalizedRecipientEmail(value string) (string, error) {
	if strings.TrimSpace(value) == "" {
		return "", fmt.Errorf("resolved email must not be empty")
	}
	parsed, err := netmail.ParseAddress(value)
	if err != nil {
		return "", fmt.Errorf("resolved email %q must be valid: %w", value, err)
	}
	if parsed.Name != "" || parsed.Address != value {
		return "", fmt.Errorf("resolved email %q must not include a display name", value)
	}

	return value, nil
}

func normalizedLocale(value string) (string, error) {
	switch {
	case strings.TrimSpace(value) == "":
		return "", fmt.Errorf("resolved locale must not be empty")
	case strings.TrimSpace(value) != value:
		return "", fmt.Errorf("resolved locale %q must not contain surrounding whitespace", value)
	default:
		return value, nil
	}
}

func payloadVariables(payloadJSON string) (json.RawMessage, error) {
	var payloadObject map[string]json.RawMessage
	if err := json.Unmarshal([]byte(payloadJSON), &payloadObject); err != nil {
		return nil, fmt.Errorf("decode payload_json: %w", err)
	}
	if payloadObject == nil {
		return nil, fmt.Errorf("payload_json must be a JSON object")
	}

	return json.RawMessage(payloadJSON), nil
}