package metastore

import (
	"encoding/json"
	"errors"
	"fmt"
	"sort"
	"strings"
	"time"

	"github.com/dgraph-io/badger/v4"

	"warpbox/lib/helpers"
)

const (
	AlertSeverityLow    = "low"
	AlertSeverityMedium = "medium"
	AlertSeverityHigh   = "high"

	AlertStatusOpen         = "open"
	AlertStatusAcknowledged = "acknowledged"
	AlertStatusClosed       = "closed"
)

func (store *Store) CreateAlert(input AlertInput) (Alert, error) {
	alert, err := normalizeAlertInput(input)
	if err != nil {
		return Alert{}, err
	}
	id, err := helpers.RandomHexID(16)
	if err != nil {
		return Alert{}, err
	}
	now := time.Now().UTC()
	alert.ID = id
	alert.Status = AlertStatusOpen
	alert.CreatedAt = now
	alert.UpdatedAt = now

	err = store.db.Update(func(txn *badger.Txn) error {
		return putJSON(txn, alertKey(alert.ID), alert)
	})
	return alert, err
}

func (store *Store) ListAlerts(filters AlertFilters) ([]Alert, error) {
	alerts := []Alert{}
	err := store.db.View(func(txn *badger.Txn) error {
		opts := badger.DefaultIteratorOptions
		opts.Prefix = []byte("alert/")
		it := txn.NewIterator(opts)
		defer it.Close()

		for it.Rewind(); it.Valid(); it.Next() {
			var alert Alert
			if err := it.Item().Value(func(data []byte) error {
				return json.Unmarshal(data, &alert)
			}); err != nil {
				return err
			}
			if alertMatchesFilters(alert, filters) {
				alerts = append(alerts, alert)
			}
		}
		return nil
	})
	if err != nil {
		return nil, err
	}
	sortAlerts(alerts, filters.Sort)
	return alerts, nil
}

func (store *Store) GetAlert(id string) (Alert, bool, error) {
	id = strings.TrimSpace(id)
	if id == "" {
		return Alert{}, false, nil
	}
	var alert Alert
	err := store.db.View(func(txn *badger.Txn) error {
		return getJSON(txn, alertKey(id), &alert)
	})
	if errors.Is(err, ErrNotFound) {
		return Alert{}, false, nil
	}
	return alert, err == nil, err
}

func (store *Store) AcknowledgeAlert(id string) error {
	return store.updateAlertStatus(id, AlertStatusAcknowledged)
}

func (store *Store) CloseAlert(id string) error {
	return store.updateAlertStatus(id, AlertStatusClosed)
}

func (store *Store) updateAlertStatus(id string, status string) error {
	id = strings.TrimSpace(id)
	if id == "" {
		return fmt.Errorf("%w: alert id cannot be empty", ErrInvalid)
	}
	status, err := normalizeAlertStatus(status)
	if err != nil {
		return err
	}
	now := time.Now().UTC()
	return store.db.Update(func(txn *badger.Txn) error {
		var alert Alert
		if err := getJSON(txn, alertKey(id), &alert); err != nil {
			return err
		}
		alert.Status = status
		alert.UpdatedAt = now
		switch status {
		case AlertStatusAcknowledged:
			alert.AcknowledgedAt = &now
		case AlertStatusClosed:
			alert.ClosedAt = &now
		}
		return putJSON(txn, alertKey(id), alert)
	})
}

func normalizeAlertInput(input AlertInput) (Alert, error) {
	title := strings.TrimSpace(input.Title)
	description := strings.TrimSpace(input.Description)
	code := strings.TrimSpace(input.Code)
	trace := strings.TrimSpace(input.Trace)
	severity, err := normalizeAlertSeverity(input.Severity)
	if err != nil {
		return Alert{}, err
	}
	if title == "" {
		return Alert{}, fmt.Errorf("%w: alert title cannot be empty", ErrInvalid)
	}
	if code == "" {
		return Alert{}, fmt.Errorf("%w: alert code cannot be empty", ErrInvalid)
	}
	if trace == "" {
		return Alert{}, fmt.Errorf("%w: alert trace cannot be empty", ErrInvalid)
	}
	metadata := input.Metadata
	if len(metadata) == 0 {
		metadata = json.RawMessage(`{}`)
	}
	var object map[string]any
	if err := json.Unmarshal(metadata, &object); err != nil {
		return Alert{}, fmt.Errorf("%w: alert metadata must be a JSON object", ErrInvalid)
	}
	normalizedMetadata, err := json.Marshal(object)
	if err != nil {
		return Alert{}, err
	}
	return Alert{
		Title:       title,
		Description: description,
		Severity:    severity,
		Code:        code,
		Trace:       trace,
		Metadata:    normalizedMetadata,
		CreatedBy:   strings.TrimSpace(input.CreatedBy),
	}, nil
}

func normalizeAlertSeverity(value string) (string, error) {
	switch strings.ToLower(strings.TrimSpace(value)) {
	case AlertSeverityLow, AlertSeverityMedium, AlertSeverityHigh:
		return strings.ToLower(strings.TrimSpace(value)), nil
	default:
		return "", fmt.Errorf("%w: invalid alert severity", ErrInvalid)
	}
}

func normalizeAlertStatus(value string) (string, error) {
	switch strings.ToLower(strings.TrimSpace(value)) {
	case AlertStatusOpen, AlertStatusAcknowledged, AlertStatusClosed:
		return strings.ToLower(strings.TrimSpace(value)), nil
	default:
		return "", fmt.Errorf("%w: invalid alert status", ErrInvalid)
	}
}

func alertMatchesFilters(alert Alert, filters AlertFilters) bool {
	query := strings.ToLower(strings.TrimSpace(filters.Query))
	if query != "" {
		haystack := strings.ToLower(strings.Join([]string{alert.Title, alert.Description, alert.Code, alert.Trace}, " "))
		if !strings.Contains(haystack, query) {
			return false
		}
	}
	if severity := strings.ToLower(strings.TrimSpace(filters.Severity)); severity != "" && severity != "all" && alert.Severity != severity {
		return false
	}
	if status := strings.ToLower(strings.TrimSpace(filters.Status)); status != "" && status != "all" && alert.Status != status {
		return false
	}
	if group := strings.ToLower(strings.TrimSpace(filters.Group)); group != "" && group != "all" && alertGroup(alert.Trace) != group {
		return false
	}
	return true
}

func sortAlerts(alerts []Alert, sortKey string) {
	switch strings.ToLower(strings.TrimSpace(sortKey)) {
	case "oldest":
		sort.Slice(alerts, func(i int, j int) bool { return alerts[i].CreatedAt.Before(alerts[j].CreatedAt) })
	case "severity":
		sort.Slice(alerts, func(i int, j int) bool {
			left := alertSeverityRank(alerts[i].Severity)
			right := alertSeverityRank(alerts[j].Severity)
			if left == right {
				return alerts[i].CreatedAt.After(alerts[j].CreatedAt)
			}
			return left > right
		})
	default:
		sort.Slice(alerts, func(i int, j int) bool { return alerts[i].CreatedAt.After(alerts[j].CreatedAt) })
	}
}

func alertSeverityRank(severity string) int {
	switch severity {
	case AlertSeverityHigh:
		return 3
	case AlertSeverityMedium:
		return 2
	default:
		return 1
	}
}

func alertGroup(trace string) string {
	trace = strings.TrimSpace(trace)
	if trace == "" {
		return "system"
	}
	before, _, found := strings.Cut(trace, ".")
	if !found || before == "" {
		return "system"
	}
	return strings.ToLower(before)
}

func alertKey(id string) []byte {
	return []byte("alert/" + strings.TrimSpace(id))
}