// Package malformedintent defines the operator-visible record used for
// malformed notification intents.
package malformedintent

import (
	"encoding/json"
	"fmt"
	"strings"
	"time"
)

// FailureCode identifies one stable malformed-intent rejection reason.
type FailureCode string

const (
	// FailureCodeInvalidIntent reports malformed top-level intent fields or an
	// invalid normalized envelope.
	FailureCodeInvalidIntent FailureCode = "invalid_intent"

	// FailureCodeInvalidPayload reports malformed or schema-invalid
	// `payload_json`.
	FailureCodeInvalidPayload FailureCode = "invalid_payload"

	// FailureCodeIdempotencyConflict reports a duplicate idempotency scope that
	// conflicts with already accepted normalized content.
	FailureCodeIdempotencyConflict FailureCode = "idempotency_conflict"

	// FailureCodeRecipientNotFound reports that a user-targeted recipient user
	// id could not be resolved through User Service.
	FailureCodeRecipientNotFound FailureCode = "recipient_not_found"
)

// Entry stores one operator-visible malformed notification-intent record.
type Entry struct {
	// StreamEntryID stores the Redis Stream entry identifier of the rejected
	// intent.
	StreamEntryID string

	// NotificationType stores the optional raw notification type extracted from
	// the rejected entry.
	NotificationType string

	// Producer stores the optional raw producer value extracted from the
	// rejected entry.
	Producer string

	// IdempotencyKey stores the optional raw idempotency key extracted from the
	// rejected entry.
	IdempotencyKey string

	// FailureCode stores the stable rejection classification.
	FailureCode FailureCode

	// FailureMessage stores the detailed validation or decode failure.
	FailureMessage string

	// RawFields stores the raw top-level stream fields captured for operator
	// inspection.
	RawFields map[string]any

	// RecordedAt stores when the malformed intent was durably recorded.
	RecordedAt time.Time
}

// IsKnown reports whether code belongs to the frozen malformed-intent
// rejection surface.
func (code FailureCode) IsKnown() bool {
	switch code {
	case FailureCodeInvalidIntent, FailureCodeInvalidPayload, FailureCodeIdempotencyConflict, FailureCodeRecipientNotFound:
		return true
	default:
		return false
	}
}

// Validate reports whether entry contains a complete malformed-intent record.
func (entry Entry) Validate() error {
	if strings.TrimSpace(entry.StreamEntryID) == "" {
		return fmt.Errorf("malformed intent stream entry id must not be empty")
	}
	if !entry.FailureCode.IsKnown() {
		return fmt.Errorf("malformed intent failure code %q is unsupported", entry.FailureCode)
	}
	if strings.TrimSpace(entry.FailureMessage) == "" {
		return fmt.Errorf("malformed intent failure message must not be empty")
	}
	if strings.TrimSpace(entry.FailureMessage) != entry.FailureMessage {
		return fmt.Errorf("malformed intent failure message must not contain surrounding whitespace")
	}
	if entry.RawFields == nil {
		return fmt.Errorf("malformed intent raw fields must not be nil")
	}
	if err := validateJSONObject("malformed intent raw fields", entry.RawFields); err != nil {
		return err
	}
	if err := validateTimestamp("malformed intent recorded at", entry.RecordedAt); err != nil {
		return err
	}

	return nil
}

func validateJSONObject(name string, value map[string]any) error {
	payload, err := json.Marshal(value)
	if err != nil {
		return fmt.Errorf("%s: %w", name, err)
	}
	if string(payload) == "null" {
		return fmt.Errorf("%s must encode as a JSON object", name)
	}

	var decoded map[string]any
	if err := json.Unmarshal(payload, &decoded); err != nil {
		return fmt.Errorf("%s: %w", name, err)
	}
	if decoded == nil {
		return fmt.Errorf("%s must encode as a JSON object", name)
	}

	return nil
}

func validateTimestamp(name string, value time.Time) error {
	if value.IsZero() {
		return fmt.Errorf("%s must not be zero", name)
	}
	if !value.Equal(value.UTC()) {
		return fmt.Errorf("%s must be UTC", name)
	}
	if !value.Equal(value.Truncate(time.Millisecond)) {
		return fmt.Errorf("%s must use millisecond precision", name)
	}

	return nil
}