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 {
	// list of [directory, filename, target path] (target path is empty, if directory marker)
	Files  [][3]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"`
}

type FileOrDir struct {
	Directory []string
	File      string
}

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)
	}

	files := make(map[string]*FileOrDir)
	for _, file := range input.Files {
		directory := file[0]
		filename := file[1]
		contents := file[2]

		dirslash := directory

		if directory != "" {
			dirslash = directory + "/"
		}

		if contents == "" {
			_, ok := files[dirslash+filename]
			if !ok {
				files[dirslash+filename] = &FileOrDir{}
			}
		} else {
			files[dirslash+filename] = &FileOrDir{File: contents}
		}

		parent, ok := files[directory]
		if !ok {
			parent = &FileOrDir{}
			files[directory] = parent
		}

		parent.Directory = append(parent.Directory, dirslash+filename)
	}

	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:])[1:]

			contents, ok := files[dir]

			if !ok {
				return nil, fs.ErrNotExist
			}

			infos := make([]fs.FileInfo, len(contents.Directory))
			for i, filename := range contents.Directory {
				file := files[filename]
				if file.File != "" {
					stat, err := os.Stat(file.File)
					if err != nil {
						return nil, err
					}

					infos[i] = &WrappedStat{FileInfo: stat, newName: path.Base(filename)}
				} else {
					infos[i] = &DirStat{path.Base(filename)}
				}
			}

			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:])[1:]
			fmt.Printf("-> OpenFile(%q)\n", pth)
			fil := files[pth]

			data, err := os.Open(fil.File)
			if err != nil {
				return data, fmt.Errorf("OpenFile(%q; %q): %w", opth, pth, 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:])[1:]

			contents, ok := files[dir]
			fmt.Printf("IsDir -> %q, %v, %v\n", dir, contents, ok)
			return ok && contents.File == ""
		},

		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 _, filedata := range input.Files {
		if filedata[2] != "" {
			filenames = append(filenames, filepath.Join(filedata[0], filedata[1]))
		}
	}

	outfiles := make(map[string]Output)

	for dir, filelist := range files {
		if filelist.File != "" {
			continue
		}

		isGo := false
		for _, file := range filelist.Directory {
			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 base == "." {
			base = ""
		}

		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 {
				dirname := filepath.Dir(match)
				if dirname == "." {
					dirname = ""
				}
				split = append(split, []string{match[len(dir)+1:], dirname, filepath.Base(match)})
			}

			out.Embeds[pattern] = split
		}

		outfiles[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(outfiles); err != nil {
		panic(err)
	}

	out.Close()
}