1 files changed, 622 insertions, 0 deletions
diff --git a/internal/revision/parser.go b/internal/revision/parser.go
new file mode 100644
index 0000000..b45a6d8
--- /dev/null
+++ b/internal/revision/parser.go
@@ -0,0 +1,622 @@
+// Package revision extracts git revision from string
+// More informations about revision : https://www.kernel.org/pub/software/scm/git/docs/gitrevisions.html
+package revision
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"regexp"
+	"strconv"
+	"time"
+)
+
+// ErrInvalidRevision is emitted if string doesn't match valid revision
+type ErrInvalidRevision struct {
+	s string
+}
+
+func (e *ErrInvalidRevision) Error() string {
+	return "Revision invalid : " + e.s
+}
+
+// Revisioner represents a revision component.
+// A revision is made of multiple revision components
+// obtained after parsing a revision string,
+// for instance revision "master~" will be converted in
+// two revision components Ref and TildePath
+type Revisioner interface {
+}
+
+// Ref represents a reference name : HEAD, master
+type Ref string
+
+// TildePath represents ~, ~{n}
+type TildePath struct {
+	Depth int
+}
+
+// CaretPath represents ^, ^{n}
+type CaretPath struct {
+	Depth int
+}
+
+// CaretReg represents ^{/foo bar}
+type CaretReg struct {
+	Regexp *regexp.Regexp
+	Negate bool
+}
+
+// CaretType represents ^{commit}
+type CaretType struct {
+	ObjectType string
+}
+
+// AtReflog represents @{n}
+type AtReflog struct {
+	Depth int
+}
+
+// AtCheckout represents @{-n}
+type AtCheckout struct {
+	Depth int
+}
+
+// AtUpstream represents @{upstream}, @{u}
+type AtUpstream struct {
+	BranchName string
+}
+
+// AtPush represents @{push}
+type AtPush struct {
+	BranchName string
+}
+
+// AtDate represents @{"2006-01-02T15:04:05Z"}
+type AtDate struct {
+	Date time.Time
+}
+
+// ColonReg represents :/foo bar
+type ColonReg struct {
+	Regexp *regexp.Regexp
+	Negate bool
+}
+
+// ColonPath represents :./<path> :<path>
+type ColonPath struct {
+	Path string
+}
+
+// ColonStagePath represents :<n>:/<path>
+type ColonStagePath struct {
+	Path  string
+	Stage int
+}
+
+// Parser represents a parser
+// use to tokenize and transform to revisioner chunks
+// a given string
+type Parser struct {
+	s                 *scanner
+	currentParsedChar struct {
+		tok token
+		lit string
+	}
+	unreadLastChar bool
+}
+
+// NewParserFromString returns a new instance of parser from a string.
+func NewParserFromString(s string) *Parser {
+	return NewParser(bytes.NewBufferString(s))
+}
+
+// NewParser returns a new instance of parser.
+func NewParser(r io.Reader) *Parser {
+	return &Parser{s: newScanner(r)}
+}
+
+// scan returns the next token from the underlying scanner
+// or the last scanned token if an unscan was requested
+func (p *Parser) scan() (token, string, error) {
+	if p.unreadLastChar {
+		p.unreadLastChar = false
+		return p.currentParsedChar.tok, p.currentParsedChar.lit, nil
+	}
+
+	tok, lit, err := p.s.scan()
+
+	p.currentParsedChar.tok, p.currentParsedChar.lit = tok, lit
+
+	return tok, lit, err
+}
+
+// unscan pushes the previously read token back onto the buffer.
+func (p *Parser) unscan() { p.unreadLastChar = true }
+
+// Parse explode a revision string into revisioner chunks
+func (p *Parser) Parse() ([]Revisioner, error) {
+	var rev Revisioner
+	var revs []Revisioner
+	var tok token
+	var err error
+
+	for {
+		tok, _, err = p.scan()
+
+		if err != nil {
+			return nil, err
+		}
+
+		switch tok {
+		case at:
+			rev, err = p.parseAt()
+		case tilde:
+			rev, err = p.parseTilde()
+		case caret:
+			rev, err = p.parseCaret()
+		case colon:
+			rev, err = p.parseColon()
+		case eof:
+			err = p.validateFullRevision(&revs)
+
+			if err != nil {
+				return []Revisioner{}, err
+			}
+
+			return revs, nil
+		default:
+			p.unscan()
+			rev, err = p.parseRef()
+		}
+
+		if err != nil {
+			return []Revisioner{}, err
+		}
+
+		revs = append(revs, rev)
+	}
+}
+
+// validateFullRevision ensures all revisioner chunks make a valid revision
+func (p *Parser) validateFullRevision(chunks *[]Revisioner) error {
+	var hasReference bool
+
+	for i, chunk := range *chunks {
+		switch chunk.(type) {
+		case Ref:
+			if i == 0 {
+				hasReference = true
+			} else {
+				return &ErrInvalidRevision{`reference must be defined once at the beginning`}
+			}
+		case AtDate:
+			if len(*chunks) == 1 || hasReference && len(*chunks) == 2 {
+				return nil
+			}
+
+			return &ErrInvalidRevision{`"@" statement is not valid, could be : <refname>@{<ISO-8601 date>}, @{<ISO-8601 date>}`}
+		case AtReflog:
+			if len(*chunks) == 1 || hasReference && len(*chunks) == 2 {
+				return nil
+			}
+
+			return &ErrInvalidRevision{`"@" statement is not valid, could be : <refname>@{<n>}, @{<n>}`}
+		case AtCheckout:
+			if len(*chunks) == 1 {
+				return nil
+			}
+
+			return &ErrInvalidRevision{`"@" statement is not valid, could be : @{-<n>}`}
+		case AtUpstream:
+			if len(*chunks) == 1 || hasReference && len(*chunks) == 2 {
+				return nil
+			}
+
+			return &ErrInvalidRevision{`"@" statement is not valid, could be : <refname>@{upstream}, @{upstream}, <refname>@{u}, @{u}`}
+		case AtPush:
+			if len(*chunks) == 1 || hasReference && len(*chunks) == 2 {
+				return nil
+			}
+
+			return &ErrInvalidRevision{`"@" statement is not valid, could be : <refname>@{push}, @{push}`}
+		case TildePath, CaretPath, CaretReg:
+			if !hasReference {
+				return &ErrInvalidRevision{`"~" or "^" statement must have a reference defined at the beginning`}
+			}
+		case ColonReg:
+			if len(*chunks) == 1 {
+				return nil
+			}
+
+			return &ErrInvalidRevision{`":" statement is not valid, could be : :/<regexp>`}
+		case ColonPath:
+			if i == len(*chunks)-1 && hasReference || len(*chunks) == 1 {
+				return nil
+			}
+
+			return &ErrInvalidRevision{`":" statement is not valid, could be : <revision>:<path>`}
+		case ColonStagePath:
+			if len(*chunks) == 1 {
+				return nil
+			}
+
+			return &ErrInvalidRevision{`":" statement is not valid, could be : :<n>:<path>`}
+		}
+	}
+
+	return nil
+}
+
+// parseAt extract @ statements
+func (p *Parser) parseAt() (Revisioner, error) {
+	var tok, nextTok token
+	var lit, nextLit string
+	var err error
+
+	tok, lit, err = p.scan()
+
+	if err != nil {
+		return nil, err
+	}
+
+	if tok != obrace {
+		p.unscan()
+
+		return Ref("HEAD"), nil
+	}
+
+	tok, lit, err = p.scan()
+
+	if err != nil {
+		return nil, err
+	}
+
+	nextTok, nextLit, err = p.scan()
+
+	if err != nil {
+		return nil, err
+	}
+
+	switch {
+	case tok == word && (lit == "u" || lit == "upstream") && nextTok == cbrace:
+		return AtUpstream{}, nil
+	case tok == word && lit == "push" && nextTok == cbrace:
+		return AtPush{}, nil
+	case tok == number && nextTok == cbrace:
+		n, _ := strconv.Atoi(lit)
+
+		return AtReflog{n}, nil
+	case tok == minus && nextTok == number:
+		n, _ := strconv.Atoi(nextLit)
+
+		t, _, err := p.scan()
+
+		if err != nil {
+			return nil, err
+		}
+
+		if t != cbrace {
+			return nil, &ErrInvalidRevision{fmt.Sprintf(`missing "}" in @{-n} structure`)}
+		}
+
+		return AtCheckout{n}, nil
+	default:
+		p.unscan()
+
+		date := lit
+
+		for {
+			tok, lit, err = p.scan()
+
+			if err != nil {
+				return nil, err
+			}
+
+			switch {
+			case tok == cbrace:
+				t, err := time.Parse("2006-01-02T15:04:05Z", date)
+
+				if err != nil {
+					return nil, &ErrInvalidRevision{fmt.Sprintf(`wrong date "%s" must fit ISO-8601 format : 2006-01-02T15:04:05Z`, date)}
+				}
+
+				return AtDate{t}, nil
+			default:
+				date += lit
+			}
+		}
+	}
+}
+
+// parseTilde extract ~ statements
+func (p *Parser) parseTilde() (Revisioner, error) {
+	var tok token
+	var lit string
+	var err error
+
+	tok, lit, err = p.scan()
+
+	if err != nil {
+		return nil, err
+	}
+
+	switch {
+	case tok == number:
+		n, _ := strconv.Atoi(lit)
+
+		return TildePath{n}, nil
+	default:
+		p.unscan()
+		return TildePath{1}, nil
+	}
+}
+
+// parseCaret extract ^ statements
+func (p *Parser) parseCaret() (Revisioner, error) {
+	var tok token
+	var lit string
+	var err error
+
+	tok, lit, err = p.scan()
+
+	if err != nil {
+		return nil, err
+	}
+
+	switch {
+	case tok == obrace:
+		r, err := p.parseCaretBraces()
+
+		if err != nil {
+			return nil, err
+		}
+
+		return r, nil
+	case tok == number:
+		n, _ := strconv.Atoi(lit)
+
+		if n > 2 {
+			return nil, &ErrInvalidRevision{fmt.Sprintf(`"%s" found must be 0, 1 or 2 after "^"`, lit)}
+		}
+
+		return CaretPath{n}, nil
+	default:
+		p.unscan()
+		return CaretPath{1}, nil
+	}
+}
+
+// parseCaretBraces extract ^{<data>} statements
+func (p *Parser) parseCaretBraces() (Revisioner, error) {
+	var tok, nextTok token
+	var lit, _ string
+	start := true
+	var re string
+	var negate bool
+	var err error
+
+	for {
+		tok, lit, err = p.scan()
+
+		if err != nil {
+			return nil, err
+		}
+
+		nextTok, _, err = p.scan()
+
+		if err != nil {
+			return nil, err
+		}
+
+		switch {
+		case tok == word && nextTok == cbrace && (lit == "commit" || lit == "tree" || lit == "blob" || lit == "tag" || lit == "object"):
+			return CaretType{lit}, nil
+		case re == "" && tok == cbrace:
+			return CaretType{"tag"}, nil
+		case re == "" && tok == emark && nextTok == emark:
+			re += lit
+		case re == "" && tok == emark && nextTok == minus:
+			negate = true
+		case re == "" && tok == emark:
+			return nil, &ErrInvalidRevision{fmt.Sprintf(`revision suffix brace component sequences starting with "/!" others than those defined are reserved`)}
+		case re == "" && tok == slash:
+			p.unscan()
+		case tok != slash && start:
+			return nil, &ErrInvalidRevision{fmt.Sprintf(`"%s" is not a valid revision suffix brace component`, lit)}
+		case tok != cbrace:
+			p.unscan()
+			re += lit
+		case tok == cbrace:
+			p.unscan()
+
+			reg, err := regexp.Compile(re)
+
+			if err != nil {
+				return CaretReg{}, &ErrInvalidRevision{fmt.Sprintf(`revision suffix brace component, %s`, err.Error())}
+			}
+
+			return CaretReg{reg, negate}, nil
+		}
+
+		start = false
+	}
+}
+
+// parseColon extract : statements
+func (p *Parser) parseColon() (Revisioner, error) {
+	var tok token
+	var err error
+
+	tok, _, err = p.scan()
+
+	if err != nil {
+		return nil, err
+	}
+
+	switch tok {
+	case slash:
+		return p.parseColonSlash()
+	default:
+		p.unscan()
+		return p.parseColonDefault()
+	}
+}
+
+// parseColonSlash extract :/<data> statements
+func (p *Parser) parseColonSlash() (Revisioner, error) {
+	var tok, nextTok token
+	var lit string
+	var re string
+	var negate bool
+	var err error
+
+	for {
+		tok, lit, err = p.scan()
+
+		if err != nil {
+			return nil, err
+		}
+
+		nextTok, _, err = p.scan()
+
+		if err != nil {
+			return nil, err
+		}
+
+		switch {
+		case tok == emark && nextTok == emark:
+			re += lit
+		case re == "" && tok == emark && nextTok == minus:
+			negate = true
+		case re == "" && tok == emark:
+			return nil, &ErrInvalidRevision{fmt.Sprintf(`revision suffix brace component sequences starting with "/!" others than those defined are reserved`)}
+		case tok == eof:
+			p.unscan()
+			reg, err := regexp.Compile(re)
+
+			if err != nil {
+				return ColonReg{}, &ErrInvalidRevision{fmt.Sprintf(`revision suffix brace component, %s`, err.Error())}
+			}
+
+			return ColonReg{reg, negate}, nil
+		default:
+			p.unscan()
+			re += lit
+		}
+	}
+}
+
+// parseColonDefault extract :<data> statements
+func (p *Parser) parseColonDefault() (Revisioner, error) {
+	var tok token
+	var lit string
+	var path string
+	var stage int
+	var err error
+	var n = -1
+
+	tok, lit, err = p.scan()
+
+	if err != nil {
+		return nil, err
+	}
+
+	nextTok, _, err := p.scan()
+
+	if err != nil {
+		return nil, err
+	}
+
+	if tok == number && nextTok == colon {
+		n, _ = strconv.Atoi(lit)
+	}
+
+	switch n {
+	case 0, 1, 2, 3:
+		stage = n
+	default:
+		path += lit
+		p.unscan()
+	}
+
+	for {
+		tok, lit, err = p.scan()
+
+		if err != nil {
+			return nil, err
+		}
+
+		switch {
+		case tok == eof && n == -1:
+			return ColonPath{path}, nil
+		case tok == eof:
+			return ColonStagePath{path, stage}, nil
+		default:
+			path += lit
+		}
+	}
+}
+
+// parseRef extract reference name
+func (p *Parser) parseRef() (Revisioner, error) {
+	var tok, prevTok token
+	var lit, buf string
+	var endOfRef bool
+	var err error
+
+	for {
+		tok, lit, err = p.scan()
+
+		if err != nil {
+			return nil, err
+		}
+
+		switch tok {
+		case eof, at, colon, tilde, caret:
+			endOfRef = true
+		}
+
+		err := p.checkRefFormat(tok, lit, prevTok, buf, endOfRef)
+
+		if err != nil {
+			return "", err
+		}
+
+		if endOfRef {
+			p.unscan()
+			return Ref(buf), nil
+		}
+
+		buf += lit
+		prevTok = tok
+	}
+}
+
+// checkRefFormat ensure reference name follow rules defined here :
+// https://git-scm.com/docs/git-check-ref-format
+func (p *Parser) checkRefFormat(token token, literal string, previousToken token, buffer string, endOfRef bool) error {
+	switch token {
+	case aslash, space, control, qmark, asterisk, obracket:
+		return &ErrInvalidRevision{fmt.Sprintf(`must not contains "%s"`, literal)}
+	}
+
+	switch {
+	case (token == dot || token == slash) && buffer == "":
+		return &ErrInvalidRevision{fmt.Sprintf(`must not start with "%s"`, literal)}
+	case previousToken == slash && endOfRef:
+		return &ErrInvalidRevision{`must not end with "/"`}
+	case previousToken == dot && endOfRef:
+		return &ErrInvalidRevision{`must not end with "."`}
+	case token == dot && previousToken == slash:
+		return &ErrInvalidRevision{`must not contains "/."`}
+	case previousToken == dot && token == dot:
+		return &ErrInvalidRevision{`must not contains ".."`}
+	case previousToken == slash && token == slash:
+		return &ErrInvalidRevision{`must not contains consecutively "/"`}
+	case (token == slash || endOfRef) && len(buffer) > 4 && buffer[len(buffer)-5:] == ".lock":
+		return &ErrInvalidRevision{"cannot end with .lock"}
+	}
+
+	return nil
+}