moth/pkg/transpile/puzzle.go

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package transpile
import (
"bufio"
"bytes"
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"context"
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"crypto/sha256"
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"encoding/json"
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"errors"
"fmt"
"io"
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"log"
"net/mail"
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"os"
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"os/exec"
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"path"
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"strconv"
"strings"
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"time"
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"github.com/russross/blackfriday/v2"
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"github.com/spf13/afero"
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"gopkg.in/yaml.v2"
)
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// AnswerResponse is handed back when we ask for an answer to be checked.
type AnswerResponse struct {
Correct bool
}
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// Puzzle contains everything about a puzzle that a client would see.
type Puzzle struct {
Pre struct {
Authors []string
Attachments []string
Scripts []string
Body string
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AnswerPattern string
AnswerHashes []string
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}
Post struct {
Objective string
Success struct {
Acceptable string
Mastery string
}
KSAs []string
}
Debug struct {
Log []string
Errors []string
Hints []string
Summary string
}
Answers []string
}
func (puzzle *Puzzle) computeAnswerHashes() {
if len(puzzle.Answers) == 0 {
return
}
puzzle.Pre.AnswerHashes = make([]string, len(puzzle.Answers))
for i, answer := range puzzle.Answers {
sum := sha256.Sum256([]byte(answer))
hexsum := fmt.Sprintf("%x", sum)
puzzle.Pre.AnswerHashes[i] = hexsum
}
}
// StaticPuzzle contains everything a static puzzle might tell us.
type StaticPuzzle struct {
Pre struct {
Authors []string
Attachments []StaticAttachment
Scripts []StaticAttachment
AnswerPattern string
}
Post struct {
Objective string
Success struct {
Acceptable string
Mastery string
}
KSAs []string
}
Debug struct {
Log []string
Errors []string
Hints []string
Summary string
}
Answers []string
}
// StaticAttachment carries information about an attached file.
type StaticAttachment struct {
Filename string // Filename presented as part of puzzle
FilesystemPath string // Filename in backing FS (URL, mothball, or local FS)
}
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// UnmarshalYAML allows a StaticAttachment to be specified as a single string.
// The way the yaml library works is weird.
func (sa *StaticAttachment) UnmarshalYAML(unmarshal func(interface{}) error) error {
if err := unmarshal(&sa.Filename); err == nil {
sa.FilesystemPath = sa.Filename
return nil
}
parts := new(struct {
Filename string
FilesystemPath string
})
if err := unmarshal(parts); err != nil {
return err
}
sa.Filename = parts.Filename
sa.FilesystemPath = parts.FilesystemPath
return nil
}
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// ReadSeekCloser provides io.Reader, io.Seeker, and io.Closer.
type ReadSeekCloser interface {
io.Reader
io.Seeker
io.Closer
}
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// PuzzleProvider establishes the functionality required to provide one puzzle.
type PuzzleProvider interface {
// Puzzle returns a Puzzle struct for the current puzzle.
Puzzle() (Puzzle, error)
// Open returns a newly-opened file.
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Open(filename string) (ReadSeekCloser, error)
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// Answer returns whether the provided answer is correct.
Answer(answer string) bool
}
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// NewFsPuzzle returns a new FsPuzzle.
func NewFsPuzzle(fs afero.Fs) PuzzleProvider {
var command string
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if info, err := fs.Stat("mkpuzzle"); !os.IsNotExist(err) {
if (info.Mode() & 0100) != 0 {
// Try to get the actual path to the executable
if pfs, ok := fs.(*RecursiveBasePathFs); ok {
if command, err = pfs.RealPath(info.Name()); err != nil {
log.Println("WARN: Unable to resolve full path to", info.Name(), pfs)
}
} else if pfs, ok := fs.(*afero.BasePathFs); ok {
if command, err = pfs.RealPath(info.Name()); err != nil {
log.Println("WARN: Unable to resolve full path to", info.Name(), pfs)
}
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}
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} else {
log.Println("WARN: mkpuzzle exists, but isn't executable.")
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}
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}
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if command != "" {
return FsCommandPuzzle{
fs: fs,
command: command,
timeout: 2 * time.Second,
}
}
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return FsPuzzle{
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fs: fs,
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}
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}
// NewFsPuzzlePoints returns a new FsPuzzle for points.
func NewFsPuzzlePoints(fs afero.Fs, points int) PuzzleProvider {
return NewFsPuzzle(NewRecursiveBasePathFs(fs, strconv.Itoa(points)))
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}
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// FsPuzzle is a single puzzle's directory.
type FsPuzzle struct {
fs afero.Fs
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mkpuzzle bool
}
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// Puzzle returns a Puzzle struct for the current puzzle.
func (fp FsPuzzle) Puzzle() (Puzzle, error) {
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var puzzle Puzzle
static, body, err := fp.staticPuzzle()
if err != nil {
return puzzle, err
}
// Convert to an exportable Puzzle
puzzle.Post = static.Post
puzzle.Debug = static.Debug
puzzle.Answers = static.Answers
puzzle.Pre.Authors = static.Pre.Authors
puzzle.Pre.Body = string(body)
puzzle.Pre.AnswerPattern = static.Pre.AnswerPattern
puzzle.Pre.Attachments = make([]string, len(static.Pre.Attachments))
for i, attachment := range static.Pre.Attachments {
puzzle.Pre.Attachments[i] = attachment.Filename
}
puzzle.Pre.Scripts = make([]string, len(static.Pre.Scripts))
for i, script := range static.Pre.Scripts {
puzzle.Pre.Scripts[i] = script.Filename
}
puzzle.computeAnswerHashes()
return puzzle, nil
}
// Open returns a newly-opened file.
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func (fp FsPuzzle) Open(name string) (ReadSeekCloser, error) {
empty := nopCloser{new(bytes.Reader)}
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static, _, err := fp.staticPuzzle()
if err != nil {
return empty, err
}
var fsPath string
for _, attachment := range append(static.Pre.Attachments, static.Pre.Scripts...) {
if attachment.Filename == name {
if attachment.FilesystemPath == "" {
fsPath = attachment.Filename
} else {
fsPath = attachment.FilesystemPath
}
}
}
if fsPath == "" {
return empty, fmt.Errorf("Not listed in attachments or scripts: %s", name)
}
return fp.fs.Open(fsPath)
}
func (fp FsPuzzle) staticPuzzle() (StaticPuzzle, []byte, error) {
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r, err := fp.fs.Open("puzzle.md")
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if err != nil {
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var err2 error
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if r, err2 = fp.fs.Open("puzzle.moth"); err2 != nil {
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return StaticPuzzle{}, nil, err
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}
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}
defer r.Close()
headerBuf := new(bytes.Buffer)
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headerParser := rfc822HeaderParser
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headerEnd := ""
scanner := bufio.NewScanner(r)
lineNo := 0
for scanner.Scan() {
line := scanner.Text()
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lineNo++
if lineNo == 1 {
if line == "---" {
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headerParser = yamlHeaderParser
headerEnd = "---"
continue
}
}
if line == headerEnd {
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headerBuf.WriteRune('\n')
break
}
headerBuf.WriteString(line)
headerBuf.WriteRune('\n')
}
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bodyBuf := new(bytes.Buffer)
for scanner.Scan() {
line := scanner.Text()
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lineNo++
bodyBuf.WriteString(line)
bodyBuf.WriteRune('\n')
}
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static, err := headerParser(headerBuf)
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if err != nil {
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return static, nil, err
}
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body := blackfriday.Run(bodyBuf.Bytes())
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return static, body, err
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}
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func legacyAttachmentParser(val []string) []StaticAttachment {
ret := make([]StaticAttachment, len(val))
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for idx, txt := range val {
parts := strings.SplitN(txt, " ", 3)
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cur := StaticAttachment{}
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cur.FilesystemPath = parts[0]
if len(parts) > 1 {
cur.Filename = parts[1]
} else {
cur.Filename = cur.FilesystemPath
}
ret[idx] = cur
}
return ret
}
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func yamlHeaderParser(r io.Reader) (StaticPuzzle, error) {
p := StaticPuzzle{}
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decoder := yaml.NewDecoder(r)
decoder.SetStrict(true)
err := decoder.Decode(&p)
return p, err
}
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func rfc822HeaderParser(r io.Reader) (StaticPuzzle, error) {
p := StaticPuzzle{}
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m, err := mail.ReadMessage(r)
if err != nil {
return p, fmt.Errorf("Parsing RFC822 headers: %v", err)
}
for key, val := range m.Header {
key = strings.ToLower(key)
switch key {
case "author":
p.Pre.Authors = val
case "pattern":
p.Pre.AnswerPattern = val[0]
case "script":
p.Pre.Scripts = legacyAttachmentParser(val)
case "file":
p.Pre.Attachments = legacyAttachmentParser(val)
case "answer":
p.Answers = val
case "summary":
p.Debug.Summary = val[0]
case "hint":
p.Debug.Hints = val
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case "solution":
p.Debug.Hints = val
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case "ksa":
p.Post.KSAs = val
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case "objective":
p.Post.Objective = val[0]
case "success.acceptable":
p.Post.Success.Acceptable = val[0]
case "success.mastery":
p.Post.Success.Mastery = val[0]
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default:
return p, fmt.Errorf("Unknown header field: %s", key)
}
}
return p, nil
}
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// Answer checks whether the given answer is correct.
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func (fp FsPuzzle) Answer(answer string) bool {
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p, _, err := fp.staticPuzzle()
if err != nil {
return false
}
for _, ans := range p.Answers {
if ans == answer {
return true
}
}
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return false
}
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// FsCommandPuzzle provides an FsPuzzle backed by running a command.
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type FsCommandPuzzle struct {
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fs afero.Fs
command string
timeout time.Duration
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}
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func (fp FsCommandPuzzle) run(command string, args ...string) ([]byte, error) {
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ctx, cancel := context.WithTimeout(context.Background(), fp.timeout)
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defer cancel()
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cmdargs := append([]string{command}, args...)
cmd := exec.CommandContext(ctx, "./"+path.Base(fp.command), cmdargs...)
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cmd.Dir = path.Dir(fp.command)
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out, err := cmd.Output()
if err, ok := err.(*exec.ExitError); ok {
stderr := strings.TrimSpace(string(err.Stderr))
return nil, fmt.Errorf("%s (%s)", stderr, err.String())
}
return out, err
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}
// Puzzle returns a Puzzle struct for the current puzzle.
func (fp FsCommandPuzzle) Puzzle() (Puzzle, error) {
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stdout, err := fp.run("puzzle")
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if exiterr, ok := err.(*exec.ExitError); ok {
return Puzzle{}, errors.New(string(exiterr.Stderr))
} else if err != nil {
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return Puzzle{}, err
}
jsdec := json.NewDecoder(bytes.NewReader(stdout))
jsdec.DisallowUnknownFields()
puzzle := Puzzle{}
if err := jsdec.Decode(&puzzle); err != nil {
return Puzzle{}, err
}
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puzzle.computeAnswerHashes()
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return puzzle, nil
}
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type nopCloser struct {
io.ReadSeeker
}
func (c nopCloser) Close() error {
return nil
}
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// Open returns a newly-opened file.
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// BUG(neale): FsCommandPuzzle.Open() reads everything into memory, and will suck for large files.
func (fp FsCommandPuzzle) Open(filename string) (ReadSeekCloser, error) {
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stdout, err := fp.run("file", filename)
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buf := nopCloser{bytes.NewReader(stdout)}
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if err != nil {
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return buf, err
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}
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return buf, nil
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}
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// Answer checks whether the given answer is correct.
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func (fp FsCommandPuzzle) Answer(answer string) bool {
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stdout, err := fp.run("answer", answer)
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if err != nil {
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log.Printf("ERROR: checking answer: %s", err)
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return false
}
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ans := AnswerResponse{}
if err := json.Unmarshal(stdout, &ans); err != nil {
log.Printf("ERROR: checking answer: %s", err)
return false
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}
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return ans.Correct
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}