package walker

import (
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"strings"

	"dirmd/internal/config"
	"dirmd/internal/filter"
)

type Entry struct {
	RelPath string
	Size    int64
}

type Result struct {
	Entries    []Entry
	AbsRoot    string
	SingleFile bool
}

func Run(cfg *config.Config) (*Result, error) {
	if cfg.SingleFile {
		return processSingleFile(cfg)
	}
	return walkDirectory(cfg)
}

func processSingleFile(cfg *config.Config) (*Result, error) {
	info, err := os.Stat(cfg.AbsRoot)
	if err != nil {
		return nil, fmt.Errorf("cannot access %s: %w", cfg.AbsRoot, err)
	}

	if info.IsDir() {
		return walkDirectory(cfg)
	}

	flt := &filter.Filter{
		MaxSize:    cfg.MaxSize,
		Extensions: cfg.Extensions,
		Ignores:    cfg.Ignores,
	}

	if flt.ShouldSkipFile(cfg.AbsRoot, filepath.Base(cfg.AbsRoot), info) {
		return nil, fmt.Errorf("file %s filtered out", cfg.AbsRoot)
	}

	return &Result{
		Entries:    []Entry{{RelPath: filepath.Base(cfg.AbsRoot), Size: info.Size()}},
		AbsRoot:    filepath.Dir(cfg.AbsRoot),
		SingleFile: true,
	}, nil

}

func walkDirectory(cfg *config.Config) (*Result, error) {
	flt := &filter.Filter{
		MaxSize:    cfg.MaxSize,
		Extensions: cfg.Extensions,
		Ignores:    cfg.Ignores,
	}

	result := &Result{AbsRoot: cfg.AbsRoot}

	err := filepath.WalkDir(cfg.AbsRoot, func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			fmt.Fprintf(os.Stderr, "warning: %v\n", err)
			return nil
		}

		rel, err := filepath.Rel(cfg.AbsRoot, path)
		if err != nil {
			return nil
		}

		depth := strings.Count(rel, string(filepath.Separator))
		if rel != "." {
			depth++
		}

		if depth > cfg.MaxDepth {
			if d.IsDir() {
				return filepath.SkipDir
			}
			return nil
		}

		if filter.IsSymlink(path) {
			if d.IsDir() {
				return filepath.SkipDir
			}
			return nil
		}

		base := filepath.Base(path)

		if d.IsDir() {
			if rel != "." && flt.ShouldSkipDir(base) {
				return filepath.SkipDir
			}
			return nil
		}

		info, err := d.Info()
		if err != nil {
			fmt.Fprintf(os.Stderr, "warning: cannot stat %s: %v\n", rel, err)
			return nil
		}

		if flt.ShouldSkipFile(path, base, info) {
			return nil
		}

		result.Entries = append(result.Entries, Entry{RelPath: rel, Size: info.Size()})
		return nil
	})

	return result, err
}