package store

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"time"
)

func ensureDir(dir string) error {
	return os.MkdirAll(dir, 0o755)
}

func readJSON[T any](path string) (T, error) {
	var v T
	data, err := os.ReadFile(path)
	if err != nil {
		return v, err
	}
	if err := json.Unmarshal(data, &v); err != nil {
		return v, err
	}
	return v, nil
}

func writeJSON(path string, v any) error {
	data, err := json.MarshalIndent(v, "", "  ")
	if err != nil {
		return err
	}
	return os.WriteFile(path, data, 0o644)
}

func removeFile(path, notFoundMsg string) error {
	if err := os.Remove(path); err != nil {
		if os.IsNotExist(err) {
			return fmt.Errorf("%s", notFoundMsg)
		}
		return err
	}
	return nil
}

func listFromDir[T any](
	dir string,
	match func(name string) bool,
	readLabel string,
	createdAt func(T) time.Time,
) ([]T, error) {
	if err := ensureDir(dir); err != nil {
		return nil, err
	}
	entries, err := os.ReadDir(dir)
	if err != nil {
		return nil, fmt.Errorf("read %s: %w", readLabel, err)
	}

	var out []T
	for _, e := range entries {
		if e.IsDir() || !match(e.Name()) {
			continue
		}
		v, err := readJSON[T](filepath.Join(dir, e.Name()))
		if err != nil {
			return nil, err
		}
		out = append(out, v)
	}

	sort.Slice(out, func(i, j int) bool {
		return createdAt(out[i]).After(createdAt(out[j]))
	})
	return out, nil
}

func findByID[T any](list []T, id string, idOf func(T) string) (T, error) {
	for _, v := range list {
		if idOf(v) == id {
			return v, nil
		}
	}
	var zero T
	return zero, fmt.Errorf("not found: %s", id)
}

func stampNew(createdAt *time.Time) time.Time {
	if createdAt.IsZero() {
		return time.Now().UTC()
	}
	return *createdAt
}