package source

import (
	"fmt"
	"io/ioutil"
	"os"
	"strings"
)

type LocalSource struct {
	root string
}

func NewLocal(root string) Source {
	return &LocalSource{
		root: strings.TrimRight(root, "/"),
	}
}

func (s *LocalSource) resolve(path string) (string, error) {
	if !strings.HasPrefix(path, "//") {
		return "", fmt.Errorf("invalid path %q, expected // prefix", path)
	}
	path = path[2:]
	if strings.HasPrefix(path, "/") {
		return "", fmt.Errorf("invalid path %q, expected // prefix", path)
	}

	return s.root + "/" + path, nil
}

func (s *LocalSource) IsFile(path string) (bool, error) {
	path, err := s.resolve(path)
	if err != nil {
		return false, err
	}
	stat, err := os.Stat(path)
	if err != nil {
		if os.IsNotExist(err) {
			return false, nil
		}
		return false, fmt.Errorf("os.Stat(%q): %w", path, err)
	}
	return !stat.IsDir(), nil
}

func (s *LocalSource) ReadFile(path string) ([]byte, error) {
	path, err := s.resolve(path)
	if err != nil {
		return nil, err
	}
	// TODO(q3k): limit size
	return ioutil.ReadFile(path)
}

func (s *LocalSource) IsDirectory(path string) (bool, error) {
	path, err := s.resolve(path)
	if err != nil {
		return false, err
	}
	stat, err := os.Stat(path)
	if err != nil {
		if os.IsNotExist(err) {
			return false, nil
		}
		return false, fmt.Errorf("os.Stat(%q): %w", path, err)
	}
	return stat.IsDir(), nil
}

func (s *LocalSource) CacheSet(dependencies []string, key string, value interface{}) {
	// Swallow writes. The local filesystem can always change underneath us and
	// we're not tracking anything, so we cannot ever keep caches.
}

func (s *LocalSource) CacheGet(key string) interface{} {
	return nil
}