From dae74317d84471f6a859117fcbba1cf546be8ea1 Mon Sep 17 00:00:00 2001
From: Charlie Stanton <charlie@shtanton.xyz>
Date: Wed, 19 Apr 2023 15:19:42 +0100
Subject: Adds parsing substitute commands, though executing them currently
 does nothing

---
 main/command.go |  8 ++++++++
 main/lex.go     | 27 +++++++++++++++++++++++++++
 main/main.go    |  5 -----
 main/parse.go   | 23 +++++++++++++++++++++++
 subex/lex.go    |  8 ++++++++
 5 files changed, 66 insertions(+), 5 deletions(-)

diff --git a/main/command.go b/main/command.go
index c61b0cd..8053b86 100644
--- a/main/command.go
+++ b/main/command.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"main/walk"
+	"main/subex"
 )
 
 type PrintValueCommand struct {}
@@ -103,6 +104,13 @@ func (cmd DeleteAllCommand) exec(state *ProgramState) {
 	state.space = nil
 }
 
+type SubstituteCommand struct {
+	subex subex.SubexState
+}
+func (cmd SubstituteCommand) exec(state *ProgramState) {
+	// TODO
+}
+
 type Command interface {
 	exec(*ProgramState)
 }
\ No newline at end of file
diff --git a/main/lex.go b/main/lex.go
index 0daf2d1..e82c309 100644
--- a/main/lex.go
+++ b/main/lex.go
@@ -147,6 +147,7 @@ const (
 	TokenNumberLiteral // A number literal
 	TokenPatternStringIndex // A string index in a pattern
 	TokenPatternIntegerIndex // An integer index in a pattern
+	TokenSubex // A subex
 )
 
 type Token struct {
@@ -269,6 +270,9 @@ func lexCommand(l *lexer) stateFunc {
 		case 'i':
 			l.emit(TokenCommand)
 			return lexMultipleLiterals
+		case 's':
+			l.emit(TokenCommand)
+			return lexSubstitution
 		case 'S':
 			l.emit(TokenCommand)
 			return lexBigSubstitution
@@ -280,6 +284,29 @@ func lexCommand(l *lexer) stateFunc {
 	return l.errorf("Expected command found something else")
 }
 
+func lexSubstitution(l *lexer) stateFunc {
+	delimiter := l.next()
+	if delimiter == eof {
+		return l.errorf("Missing subex in substitution command")
+	}
+	l.emit(TokenSubstituteDelimiter)
+	loop: for {
+		r := l.next()
+		switch r {
+			case delimiter:
+				l.backup()
+				l.emit(TokenSubex)
+				l.next()
+				l.emit(TokenSubstituteDelimiter)
+				break loop
+			case eof:
+				return l.errorf("Missing closing substitution delimiter")
+			default:
+		}
+	}
+	return lexCommand
+}
+
 func lexBigSubstitution(l *lexer) stateFunc {
 	delimiter := l.next()
 	if delimiter == eof || isAlphaNumeric(delimiter) {
diff --git a/main/main.go b/main/main.go
index 3da414d..902c5b9 100644
--- a/main/main.go
+++ b/main/main.go
@@ -3,7 +3,6 @@ package main
 import (
 	"os"
 	"bufio"
-	"main/subex"
 	"main/walk"
 )
 
@@ -17,10 +16,6 @@ type ProgramState struct {
 }
 
 func main() {
-	subex.Main()
-}
-
-func mainISH() {
 	quiet := false
 	var input string
 	hasInput := false
diff --git a/main/parse.go b/main/parse.go
index 73c7913..bf2f0ac 100644
--- a/main/parse.go
+++ b/main/parse.go
@@ -5,6 +5,7 @@ import (
 	"strconv"
 	"fmt"
 	"main/walk"
+	"main/subex"
 )
 
 type parser struct {
@@ -202,6 +203,25 @@ func (p *parser) parseLiterals() (items []walk.WalkItem) {
 	return items
 }
 
+func (p *parser) parseSubex() subex.SubexState {
+	delim := p.next()
+	if delim.typ != TokenSubstituteDelimiter {
+		panic("Missing substitute delimiter")
+	}
+	subexProgramToken := p.next()
+	if subexProgramToken.typ != TokenSubex {
+		panic("Missing subex from substitution")
+	}
+	reader := subex.NewStringRuneReader(subexProgramToken.val)
+	subexAST := subex.Parse(reader)
+	subex := subex.CompileTransducer(subexAST)
+	delim = p.next()
+	if delim.typ != TokenSubstituteDelimiter {
+		panic("Missing end substitute delimiter")
+	}
+	return subex
+}
+
 func (p *parser) parseBasicCommand(commandChar rune) Command {
 	switch commandChar {
 		case 'p':
@@ -212,6 +232,9 @@ func (p *parser) parseBasicCommand(commandChar rune) Command {
 			return NextCommand{}
 		case 'N':
 			return AppendNextCommand{}
+		case 's':
+			subex := p.parseSubex()
+			return SubstituteCommand {subex: subex}
 		case 'i':
 			items := p.parseLiterals()
 			return PrintLiteralsCommand {items: items}
diff --git a/subex/lex.go b/subex/lex.go
index 74bf370..0f00a99 100644
--- a/subex/lex.go
+++ b/subex/lex.go
@@ -22,3 +22,11 @@ func (l *StringRuneReader) Next() rune {
 func (l *StringRuneReader) Rewind() {
 	l.pos -= l.width
 }
+
+func NewStringRuneReader(input string) RuneReader {
+	return &StringRuneReader {
+		input: input,
+		pos: 0,
+		width: 0,
+	}
+}
-- 
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