package main

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

	"go.jolheiser.com/imp/format"

	"gitea.com/jolheiser/globber"
	gofumptFormat "mvdan.cc/gofumpt/format"
)

func runImp(root, ignore string, write, gofumpt, gofumptExtra bool) error {
	mod, err := modInfo()
	if err != nil {
		return err
	}
	globs, err := globber.ParseFile(ignore)
	if err != nil {
		if !errors.Is(err, fs.ErrNotExist) {
			return err
		}
		globs = globber.New()
	}

	var failed bool
	if err := filepath.Walk(root, func(walkPath string, walkInfo os.FileInfo, walkErr error) error {
		if walkErr != nil {
			return walkErr
		}

		walkPath = filepath.ToSlash(walkPath)

		if s := checkSkip(walkPath, walkInfo, globs); s != CHECK {
			if s == SKIPDIR {
				return filepath.SkipDir
			}
			return nil
		}

		data, err := os.ReadFile(walkPath)
		if err != nil {
			return fmt.Errorf("could not read file %q: %w", walkPath, err)
		}

		formatted, err := impFormat(data, mod, gofumpt, gofumptExtra)
		if err != nil && !errors.Is(err, format.ErrNoImports) {
			return fmt.Errorf("could not format file %q: %w", walkPath, err)
		}

		if write {
			if err := os.WriteFile(walkPath, formatted, walkInfo.Mode()); err != nil {
				return fmt.Errorf("could not write file %q: %w", walkPath, err)
			}
			return nil
		}

		if !bytes.Equal(data, formatted) {
			failed = true
		}
		return nil
	}); err != nil {
		return err
	}
	if failed {
		return errors.New("imports are formatted incorrectly; this can be fixed with the `--write` flag")
	}
	return nil
}

func impFormat(src []byte, mod module, gofumpt, gofumptExtra bool) ([]byte, error) {
	formatted, err := format.Source(src, mod.Path)
	if err != nil {
		return src, err
	}
	if gofumpt {
		formatted, err = gofumptFormat.Source(formatted, gofumptFormat.Options{
			LangVersion: mod.GoVersion,
			ModulePath:  mod.Path,
			ExtraRules:  gofumptExtra,
		})
		if err != nil {
			return src, err
		}
	}
	return formatted, nil
}

func checkSkip(walkPath string, walkInfo os.FileInfo, globs *globber.GlobSet) walkStatus {
	// Skip current directory
	if strings.EqualFold(walkPath, ".") {
		return SKIP
	}

	// Skip hidden paths (starting with ".")
	if strings.HasPrefix(walkPath, ".") {
		if walkInfo.IsDir() {
			return SKIPDIR
		}
		return SKIP
	}

	// Skip directories
	if walkInfo.IsDir() {
		return SKIP
	}

	// Skip non-Go files
	if !strings.HasSuffix(walkInfo.Name(), ".go") {
		return SKIP
	}

	// Skip included (ignored) globs
	i, e := globs.Explain(walkPath)
	if len(i) > 0 && len(e) == 0 {
		return SKIP
	}

	return CHECK
}

type walkStatus int

const (
	SKIP walkStatus = iota
	SKIPDIR
	CHECK
)