package main

import (
	"encoding/json"
	"fmt"
	"go/build"
	"io"
	"io/fs"
	"os"
	"path"
	"path/filepath"
	"sort"
	"strings"
	"time"
)

type WrappedStat struct {
	fs.FileInfo
	newName string // meow
}

func (s *WrappedStat) Name() string {
	return s.newName
}

type DirStat struct {
	name string
}

func (s *DirStat) Name() string {
	return s.name
}

func (s *DirStat) Size() int64 {
	return 1
}

func (s *DirStat) Mode() fs.FileMode {
	return fs.FileMode(fs.ModeDir | 0777)
}

func (s *DirStat) ModTime() time.Time {
	return time.Time{}
}

func (s *DirStat) IsDir() bool {
	return true
}

func (s *DirStat) Sys() any {
	return "zilch"
}

type Input struct {
	// directory -> filename -> path
	Files  map[string]map[string]string `json:"files"`
	GOARCH string                       `json:"GOARCH"`
	GOOS   string                       `json:"GOOS"`
}

type Output struct {
	Name    string                `json:"name"`
	GoFiles []string              `json:"goFiles"`
	SFiles  []string              `json:"sFiles"`
	Imports []string              `json:"imports"`
	Embeds  map[string][][]string `json:"embeds"`
}

func main() {
	inputFile, err := os.Open(os.Args[1])
	if err != nil {
		panic(err)
	}

	var input Input
	err = json.NewDecoder(inputFile).Decode(&input)
	if err != nil {
		panic(err)
	}
	ctx := build.Context{
		GOARCH:      input.GOARCH,
		GOOS:        input.GOOS,
		Compiler:    "gc",
		ToolTags:    build.Default.ToolTags,
		ReleaseTags: build.Default.ReleaseTags,
		ReadDir: func(dir string) ([]fs.FileInfo, error) {
			fmt.Printf("ReadDir(%q)\n", dir)
			if !strings.HasPrefix(dir, "/code") {
				return nil, fs.ErrNotExist
			}

			dir = path.Clean(dir[5:])
			if dir == "." {
				dir = "/"
			}

			if !strings.HasSuffix(dir, "/") {
				dir += "/"
			}

			dircontents, ok := input.Files[dir]
			if !ok {
				return nil, fs.ErrNotExist
			}

			infos := make([]fs.FileInfo, len(dircontents))
			i := 0
			for name, file := range dircontents {
				stat, err := os.Stat(file)
				if err != nil {
					return nil, err
				}

				infos[i] = &WrappedStat{FileInfo: stat, newName: name}
				i = i + 1
			}

			for key := range input.Files {
				if path.Dir(key) == dir {
					base := path.Base(key)
					if strings.HasPrefix(base, ".") || strings.HasPrefix(base, "_") || base == "testdata" {
						continue
					}

					infos = append(infos, &DirStat{base})
				}
			}

			return infos, nil
		},

		OpenFile: func(pth string) (io.ReadCloser, error) {
			opth := pth
			fmt.Printf("OpenFile(%q)\n", pth)
			if !strings.HasPrefix(pth, "/code") {
				return nil, fs.ErrNotExist
			}

			pth = path.Clean(pth[5:])
			dirname, fname := path.Split(pth)
			if dirname == "." {
				dirname = "/"
			}
			dir := input.Files[dirname]

			data, err := os.Open(dir[fname])
			if err != nil {
				return data, fmt.Errorf("OpenFile(%q; %q[%q]; %q): %w", opth, dirname, fname, dir[fname], err)
			}
			return data, err
		},

		IsDir: func(dir string) bool {
			fmt.Printf("IsDir(%q)\n", dir)
			if !strings.HasPrefix(dir, "/code") {
				return false
			}

			dir = path.Clean(dir[5:])
			if dir == "." {
				dir = "/"
			}

			if !strings.HasSuffix(dir, "/") {
				dir += "/"
			}

			_, ok := input.Files[dir]
			fmt.Printf("IsDir -> %q, %v\n", dir, ok)
			return ok
		},

		HasSubdir: func(root, dir string) (rel string, ok bool) {
			root = path.Clean(root)
			dir = path.Clean(dir)

			return strings.CutPrefix(dir, root)
		},
	}

	var filenames []string
	for dirname, files := range input.Files {
		for filename := range files {
			filenames = append(filenames, filepath.Join(dirname, filename))
		}
	}

	files := make(map[string]Output)

	for dir, filelist := range input.Files {
		isGo := false
		for file := range filelist {
			if strings.HasSuffix(file, ".go") {
				isGo = true
				break
			}
		}

		fmt.Printf("Checking %q..\n", dir)
		if strings.Contains(dir, "/.") || strings.Contains(dir, "/_") || strings.Contains(dir, "/testdata/") {
			fmt.Printf("  skipping; \n")
			continue
		}

		base := path.Base(dir)

		if !isGo || strings.HasPrefix(base, "_") || strings.HasPrefix(base, ".") || base == "testdata" {
			fmt.Printf("  skipping (not go)\n")
			continue
		}

		pkg, err := ctx.Import(".", path.Clean("/code"+dir), 0)
		if err != nil {
			if _, ok := err.(*build.NoGoError); ok {
				continue
			}

			panic(err)
		}

		out := Output{
			Name:    pkg.Name,
			Imports: pkg.Imports,
			GoFiles: pkg.GoFiles,
			SFiles:  pkg.SFiles,
			Embeds:  make(map[string][][]string),
		}

		// _test only, or so
		if len(pkg.GoFiles) == 0 {
			continue
		}

		sort.Strings(out.Imports)
		sort.Strings(out.GoFiles)
		sort.Strings(out.SFiles)
		sort.Strings(pkg.EmbedPatterns)

		for _, pattern := range pkg.EmbedPatterns {
			matchedFiles := []string{}

			// TODO: proper matching
			if strings.HasPrefix(pattern, "all:") {
				pattern = pattern[4:]
			}

			fullPattern := filepath.Join(dir, pattern)
			for _, file := range filenames {
				if ok, _ := filepath.Match(fullPattern, file); ok {
					matchedFiles = append(matchedFiles, file)
				}
			}

			if len(matchedFiles) == 0 {
				dirpattern := fullPattern + "/"
				for _, file := range filenames {
					if strings.HasPrefix(file, dirpattern) {
						matchedFiles = append(matchedFiles, file)
					}

					if file == fullPattern {
						matchedFiles = append(matchedFiles, file)
					}
				}
			}

			sort.Strings(matchedFiles)
			var split [][]string
			for _, match := range matchedFiles {
				split = append(split, []string{match[len(dir):], filepath.Dir(match) + "/", filepath.Base(match)})
			}

			out.Embeds[pattern] = split
		}

		files[dir] = out
	}

	out, err := os.OpenFile(os.Getenv("out"), os.O_CREATE|os.O_RDWR, 0666)
	if err != nil {
		panic(err)
	}

	if err := json.NewEncoder(out).Encode(files); err != nil {
		panic(err)
	}

	out.Close()
}