package settings

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

// MaxNodeAuditEvents is the retention cap for node-audit.json.
const MaxNodeAuditEvents = 1000

// LoadNodeAudit reads and parses node-audit.json from dir.
func LoadNodeAudit(dir string) (NodeAuditStore, error) {
	path := filepath.Join(dir, NodeAuditFileName)
	payload, err := os.ReadFile(path)
	if err != nil {
		return NodeAuditStore{}, err
	}

	var store NodeAuditStore
	if err := json.Unmarshal(payload, &store); err != nil {
		return NodeAuditStore{}, fmt.Errorf("parse node audit: %w", err)
	}
	if store.Events == nil {
		store.Events = []NodeAuditEvent{}
	}
	return store, nil
}

// LoadNodeAuditOrEmpty returns an empty store when node-audit.json is missing.
func LoadNodeAuditOrEmpty(dir string) (NodeAuditStore, error) {
	store, err := LoadNodeAudit(dir)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return NodeAuditStore{Events: []NodeAuditEvent{}}, nil
		}
		return NodeAuditStore{}, err
	}
	return store, nil
}

// SaveNodeAudit writes node-audit.json to dir with mode 0640.
func SaveNodeAudit(dir string, store NodeAuditStore) error {
	if err := ensureConfigDir(dir); err != nil {
		return err
	}
	if store.Events == nil {
		store.Events = []NodeAuditEvent{}
	}

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

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

// AppendNodeAuditEvent appends event and trims to MaxNodeAuditEvents (newest kept).
func AppendNodeAuditEvent(dir string, event NodeAuditEvent) error {
	store, err := LoadNodeAuditOrEmpty(dir)
	if err != nil {
		return err
	}
	store.Events = append(store.Events, event)
	if len(store.Events) > MaxNodeAuditEvents {
		store.Events = store.Events[len(store.Events)-MaxNodeAuditEvents:]
	}
	return SaveNodeAudit(dir, store)
}