package adapters

import (
	"errors"
	"os"
	"path/filepath"
	"strings"
	"time"
)

type LocalFsAdapter struct {
	roots []string
}

func (l LocalFsAdapter) readDir(path string, root string) (FsResponse, error) {
	dirInfo, err := os.Stat(path)
	if err != nil {
		return FsResponse{}, err
	}

	entries, err := os.ReadDir(path)
	if err != nil {
		return FsResponse{}, err
	}

	out := make([]FsDirEntry, 0, len(entries))
	for _, e := range entries {
		info, _ := e.Info()

		entryType := "dir"
		if !e.IsDir() {
			entryType = contentTypeFor(e.Name())
		}

		out = append(out, FsDirEntry{
			Name:    e.Name(),
			Type:    entryType,
			IsDir:   e.IsDir(),
			ModTime: info.ModTime(),
		})
	}

	relPath, err := filepath.Rel(root, path)
	if err != nil {
		return FsResponse{}, err
	}
	if relPath == "." {
		relPath = ""
	}

	responsePath := "/" + filepath.ToSlash(filepath.Join(filepath.Base(root), relPath))

	return FsResponse{
		Dir: &FsDir{
			Files:   out,
			Name:    responsePath,
			ModTime: dirInfo.ModTime(),
		},
	}, nil
}

func (l LocalFsAdapter) readFile(path string, root string) (FsResponse, error) {
	fi, err := os.Stat(path)
	if err != nil {
		return FsResponse{}, err
	}

	data, err := os.ReadFile(path)
	if err != nil {
		return FsResponse{}, err
	}

	relPath, err := filepath.Rel(root, path)
	if err != nil {
		return FsResponse{}, err
	}

	responsePath := "/" + filepath.ToSlash(filepath.Join(filepath.Base(root), relPath))

	return FsResponse{
		File: &FsFile{
			Name:    responsePath,
			Type:    contentTypeFor(path),
			ModTime: fi.ModTime(),
			Content: data,
		},
	}, nil
}

func (l LocalFsAdapter) Read(path string) (FsResponse, error) {
	if path == "/" {
		entries := make([]FsDirEntry, 0, len(l.roots))
		var latestModTime time.Time
		for _, r := range l.roots {
			info, err := os.Stat(r)
			if err != nil {
				continue
			}
			entries = append(entries, FsDirEntry{
				Name:    filepath.Base(r),
				Type:    "dir",
				IsDir:   true,
				ModTime: info.ModTime(),
			})
			if info.ModTime().After(latestModTime) {
				latestModTime = info.ModTime()
			}
		}

		return FsResponse{
			Dir: &FsDir{
				Files:   entries,
				Name:    "/",
				ModTime: latestModTime,
			},
		}, nil
	}

	pathParts := strings.Split(strings.Trim(path, "/"), "/")
	if len(pathParts) == 0 || pathParts[0] == "" {
		return FsResponse{}, ErrNotFound
	}

	rootIdentifier := pathParts[0]
	var targetRoot string
	for _, r := range l.roots {
		if filepath.Base(r) == rootIdentifier {
			targetRoot = r
			break
		}
	}

	if targetRoot == "" {
		return FsResponse{}, ErrNotFound
	}

	subPath := filepath.Join(pathParts[1:]...)
	target := filepath.Join(targetRoot, subPath)

	absTarget, err := filepath.Abs(target)
	if err != nil {
		return FsResponse{}, err
	}
	absRoot, err := filepath.Abs(targetRoot)
	if err != nil {
		return FsResponse{}, err
	}
	if !strings.HasPrefix(absTarget, absRoot) {
		return FsResponse{}, errors.New("path escapes root")
	}

	fi, err := os.Stat(target)
	if err != nil {
		if os.IsNotExist(err) {
			return FsResponse{}, ErrNotFound
		}

		return FsResponse{}, err
	}

	if fi.IsDir() {
		return l.readDir(target, targetRoot)
	}

	return l.readFile(target, targetRoot)
}

func (LocalFsAdapter) Write(path string, content []byte) error {
	return nil
}

func NewLocalFsAdapter(roots []string) (FileAdapter, error) {
	return LocalFsAdapter{
		roots: roots,
	}, nil
}