package settings

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"time"
)

var diskSafeFilenamePattern = regexp.MustCompile(`[^A-Za-z0-9._-]+`)

// LoadNodeActionGroups reads and parses node-action-groups.json from dir.
func LoadNodeActionGroups(dir string) (NodeActionGroupStore, error) {
	path := filepath.Join(dir, NodeActionGroupsFileName)
	payload, err := os.ReadFile(path)
	if err != nil {
		return NodeActionGroupStore{}, err
	}

	var store NodeActionGroupStore
	if err := json.Unmarshal(payload, &store); err != nil {
		return NodeActionGroupStore{}, fmt.Errorf("parse node action groups: %w", err)
	}
	normalizeNodeActionGroupStore(&store)
	return store, nil
}

// LoadNodeActionGroupsOrEmpty returns an empty store when the file is missing.
func LoadNodeActionGroupsOrEmpty(dir string) (NodeActionGroupStore, error) {
	store, err := LoadNodeActionGroups(dir)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return NodeActionGroupStore{Groups: []NodeActionGroup{}}, nil
		}
		return NodeActionGroupStore{}, err
	}
	return store, nil
}

// SaveNodeActionGroups writes node-action-groups.json to dir with mode 0640.
func SaveNodeActionGroups(dir string, store NodeActionGroupStore) error {
	if err := ensureConfigDir(dir); err != nil {
		return err
	}
	normalizeNodeActionGroupStore(&store)

	payload, err := json.MarshalIndent(store, "", "  ")
	if err != nil {
		return fmt.Errorf("encode node action groups: %w", err)
	}
	payload = append(payload, '\n')

	path := filepath.Join(dir, NodeActionGroupsFileName)
	if err := os.WriteFile(path, payload, 0o640); err != nil {
		return fmt.Errorf("write node action groups: %w", err)
	}
	return nil
}

func normalizeNodeActionGroupStore(store *NodeActionGroupStore) {
	if store.Groups == nil {
		store.Groups = []NodeActionGroup{}
	}
	for index := range store.Groups {
		if store.Groups[index].Items == nil {
			store.Groups[index].Items = []NodeActionItem{}
		}
		if store.Groups[index].Schedule.Times == nil {
			store.Groups[index].Schedule.Times = []ActionGroupTimeSpec{}
		}
		for itemIndex := range store.Groups[index].Items {
			if store.Groups[index].Items[itemIndex].Env == nil {
				store.Groups[index].Items[itemIndex].Env = []ActionEnvVar{}
			}
		}
	}
}

// DiskSafeFilename converts a group name into a safe filename stem.
func DiskSafeFilename(name string) string {
	trimmed := strings.TrimSpace(name)
	if trimmed == "" {
		return "unnamed"
	}
	safe := diskSafeFilenamePattern.ReplaceAllString(trimmed, "_")
	safe = strings.Trim(safe, "._-")
	if safe == "" {
		return "unnamed"
	}
	if len(safe) > 120 {
		safe = safe[:120]
	}
	return safe
}

// FindNodeActionGroupIndex returns the index of a group by id, or -1.
func FindNodeActionGroupIndex(groups []NodeActionGroup, groupID string) int {
	for index := range groups {
		if groups[index].ID == groupID {
			return index
		}
	}
	return -1
}

// FindNodeActionItemIndex returns the index of an item by id, or -1.
func FindNodeActionItemIndex(items []NodeActionItem, itemID string) int {
	for index := range items {
		if items[index].ID == itemID {
			return index
		}
	}
	return -1
}

// GroupsForNode returns groups belonging to nodeID.
func GroupsForNode(store NodeActionGroupStore, nodeID string) []NodeActionGroup {
	result := make([]NodeActionGroup, 0)
	for _, group := range store.Groups {
		if group.NodeID == nodeID {
			result = append(result, group)
		}
	}
	return result
}

// LibraryActionInUse reports whether any group item still references actionID as a library source.
// Local clones (source local) do not count even if they previously came from that action.
func LibraryActionInUse(store NodeActionGroupStore, actionID string) bool {
	actionID = strings.TrimSpace(actionID)
	if actionID == "" {
		return false
	}
	for _, group := range store.Groups {
		for _, item := range group.Items {
			if item.Source == ActionItemSourceLibrary && item.LibraryActionID == actionID {
				return true
			}
		}
	}
	return false
}

// UpdateGroupLastRunAt sets LastRunAt and UpdatedAt for a group and saves.
func UpdateGroupLastRunAt(dir string, groupID string, at time.Time) error {
	store, err := LoadNodeActionGroupsOrEmpty(dir)
	if err != nil {
		return err
	}
	index := FindNodeActionGroupIndex(store.Groups, groupID)
	if index < 0 {
		return fmt.Errorf("action group not found")
	}
	runAt := at.UTC()
	store.Groups[index].LastRunAt = &runAt
	store.Groups[index].UpdatedAt = runAt
	return SaveNodeActionGroups(dir, store)
}

// IsScheduleDue reports whether the group should run at now given its schedule and LastRunAt.
func IsScheduleDue(group NodeActionGroup, now time.Time) bool {
	schedule := group.Schedule
	if !schedule.Enabled {
		return false
	}
	localNow := now.In(time.Local)

	switch schedule.Kind {
	case ActionGroupScheduleInterval:
		if schedule.EverySeconds < 1 {
			return false
		}
		if group.LastRunAt == nil {
			return true
		}
		elapsed := localNow.Sub(group.LastRunAt.In(time.Local))
		return elapsed >= time.Duration(schedule.EverySeconds)*time.Second
	case ActionGroupScheduleTimes:
		if len(schedule.Times) == 0 {
			return false
		}
		for _, spec := range schedule.Times {
			if !timeSpecMatches(spec, localNow) {
				continue
			}
			if group.LastRunAt == nil {
				return true
			}
			lastLocal := group.LastRunAt.In(time.Local)
			// Fire once per matching minute window.
			sameMinute := lastLocal.Year() == localNow.Year() &&
				lastLocal.YearDay() == localNow.YearDay() &&
				lastLocal.Hour() == localNow.Hour() &&
				lastLocal.Minute() == localNow.Minute()
			if !sameMinute {
				return true
			}
		}
		return false
	default:
		return false
	}
}

func timeSpecMatches(spec ActionGroupTimeSpec, now time.Time) bool {
	hour, minute, ok := parseHHMM(spec.Time)
	if !ok {
		return false
	}
	if now.Hour() != hour || now.Minute() != minute {
		return false
	}
	if len(spec.DaysOfWeek) == 0 {
		return true
	}
	weekday := int(now.Weekday())
	for _, day := range spec.DaysOfWeek {
		if day == weekday {
			return true
		}
	}
	return false
}

func parseHHMM(value string) (hour int, minute int, ok bool) {
	parts := strings.Split(strings.TrimSpace(value), ":")
	if len(parts) != 2 {
		return 0, 0, false
	}
	if _, err := fmt.Sscanf(parts[0], "%d", &hour); err != nil {
		return 0, 0, false
	}
	if _, err := fmt.Sscanf(parts[1], "%d", &minute); err != nil {
		return 0, 0, false
	}
	if hour < 0 || hour > 23 || minute < 0 || minute > 59 {
		return 0, 0, false
	}
	return hour, minute, true
}