Add lex mode

lex mode is a feature that separates transition tables per each mode.
The lexer starts from an initial state indicated by `initial_state` field and
transitions between modes according to `push` and `pop` fields.
The initial state will always be `default`.
Currently, maleeni doesn't provide the ability to change the initial state.
You can specify the modes of each lex entry using `modes` field.
When the mode isn't indicated explicitly, the entries have `default` mode.

1 files changed, 82 insertions, 2 deletions

diff --git a/compiler/compiler.go b/compiler/compiler.go
index 15f42f3..6f878c5 100644
--- a/compiler/compiler.go
+++ b/compiler/compiler.go
@@ -42,12 +42,71 @@ func Compile(lexspec *spec.LexSpec, opts ...compilerOption) (*spec.CompiledLexSp
 		}
 	}
 
+	modeEntries, modes, modeNums := groupEntriesByLexMode(lexspec.Entries)
+
+	modeSpecs := []*spec.CompiledLexModeSpec{
+		nil,
+	}
+	for i, es := range modeEntries[1:] {
+		modeName := modes[i+1]
+		config.logger.Log("Compile %v mode:", modeName)
+		modeSpec, err := compile(es, modeNums, config)
+		if err != nil {
+			return nil, fmt.Errorf("failed to compile in %v mode: %w", modeName, err)
+		}
+		modeSpecs = append(modeSpecs, modeSpec)
+	}
+
+	return &spec.CompiledLexSpec{
+		InitialMode: spec.LexModeNumDefault,
+		Modes:       modes,
+		Specs:       modeSpecs,
+	}, nil
+}
+
+func groupEntriesByLexMode(entries []*spec.LexEntry) ([][]*spec.LexEntry, []spec.LexModeName, map[spec.LexModeName]spec.LexModeNum) {
+	modes := []spec.LexModeName{
+		spec.LexModeNameNil,
+		spec.LexModeNameDefault,
+	}
+	modeNums := map[spec.LexModeName]spec.LexModeNum{
+		spec.LexModeNameNil:     spec.LexModeNumNil,
+		spec.LexModeNameDefault: spec.LexModeNumDefault,
+	}
+	lastModeNum := spec.LexModeNumDefault
+	modeEntries := [][]*spec.LexEntry{
+		nil,
+		[]*spec.LexEntry{},
+	}
+	for _, e := range entries {
+		ms := e.Modes
+		if len(ms) == 0 {
+			ms = []spec.LexModeName{
+				spec.LexModeNameDefault,
+			}
+		}
+		for _, mode := range ms {
+			num, ok := modeNums[mode]
+			if !ok {
+				num = lastModeNum.Succ()
+				lastModeNum = num
+				modeNums[mode] = num
+				modes = append(modes, mode)
+				modeEntries = append(modeEntries, []*spec.LexEntry{})
+			}
+			modeEntries[num] = append(modeEntries[num], e)
+		}
+	}
+	return modeEntries, modes, modeNums
+}
+
+func compile(entries []*spec.LexEntry, modeNums map[spec.LexModeName]spec.LexModeNum, config *compilerConfig) (*spec.CompiledLexModeSpec, error) {
 	var kinds []spec.LexKind
 	var patterns map[int][]byte
 	{
 		kinds = append(kinds, spec.LexKindNil)
 		patterns = map[int][]byte{}
-		for i, e := range lexspec.Entries {
+		for i, e := range entries {
 			kinds = append(kinds, e.Kind)
 			patterns[i+1] = []byte(e.Pattern)
 		}
@@ -58,6 +117,25 @@ func Compile(lexspec *spec.LexSpec, opts ...compilerOption) (*spec.CompiledLexSp
 		}
 	}
 
+	push := []spec.LexModeNum{
+		spec.LexModeNumNil,
+	}
+	pop := []int{
+		0,
+	}
+	for _, e := range entries {
+		pushV := spec.LexModeNumNil
+		if e.Push != "" {
+			pushV = modeNums[e.Push]
+		}
+		push = append(push, pushV)
+		popV := 0
+		if e.Pop {
+			popV = 1
+		}
+		pop = append(pop, popV)
+	}
+
 	var root astNode
 	var symTab *symbolTable
 	{
@@ -90,8 +168,10 @@ func Compile(lexspec *spec.LexSpec, opts ...compilerOption) (*spec.CompiledLexSp
 		}
 	}
 
-	return &spec.CompiledLexSpec{
+	return &spec.CompiledLexModeSpec{
 		Kinds: kinds,
+		Push:  push,
+		Pop:   pop,
 		DFA:   tranTab,
 	}, nil
 }