From b5a31e7775b31c943389ec90ee849944ab7c3811 Mon Sep 17 00:00:00 2001
From: TakshakRamteke <takshakramteke0708@gmail.com>
Date: Fri, 29 Nov 2024 01:42:48 +0530
Subject: [PATCH] FEAT : added a simple compiler and support for commands

---
 main.go | 102 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 95 insertions(+), 7 deletions(-)

diff --git a/main.go b/main.go
index 75d4415..e14f472 100644
--- a/main.go
+++ b/main.go
@@ -1,8 +1,30 @@
 package main
 
 import (
+	"bufio"
 	"fmt"
+	"io"
 	"os"
+	"strings"
+)
+
+type metaCommandResults int
+type prepareResults int
+type statementType int
+
+const (
+	metaCommandSuccess metaCommandResults = iota
+	metaCommandUnrecognised
+)
+
+const (
+	prepareSuccess prepareResults = iota
+	prepareUnrecognised
+)
+
+const (
+	statementSelect statementType = iota
+	statementInsert
 )
 
 type inputBuffer struct {
@@ -11,6 +33,44 @@ type inputBuffer struct {
 	inputLength  int
 }
 
+type statement struct {
+	stype statementType
+}
+
+func doMetaCommands(inputBuffer inputBuffer) metaCommandResults {
+	metacommand := metaCommandUnrecognised
+	if inputBuffer.buffer == ".exit" {
+		fmt.Println("bye!")
+		os.Exit(0)
+	} else {
+		metacommand = metaCommandUnrecognised
+	}
+	return metacommand
+}
+
+func prepareStatements(inputBuffer inputBuffer, statement *statement) prepareResults {
+	if strings.Split(inputBuffer.buffer, " ")[0] == "insert" {
+		statement.stype = statementInsert
+		return prepareSuccess
+	}
+	if strings.Split(inputBuffer.buffer, " ")[0] == "select" {
+		statement.stype = statementSelect
+		return prepareSuccess
+	}
+	return prepareUnrecognised
+}
+
+func executeStatement(statement *statement) {
+	switch statement.stype {
+	case statementInsert:
+		fmt.Println("This is where the logic of insert statement should go")
+		break
+	case statementSelect:
+		fmt.Println("This is where the logic of select statement should go")
+		break
+	}
+}
+
 func createInputBuffer() inputBuffer {
 	newInputBuffer := inputBuffer{"", 0, 0}
 	return newInputBuffer
@@ -21,7 +81,21 @@ func printConsole() {
 }
 
 func readConsole(inputBuffer inputBuffer) inputBuffer {
-	fmt.Scanf("%s", &inputBuffer.buffer)
+	var stdin *bufio.Reader
+	var line []rune
+	stdin = bufio.NewReader(os.Stdin)
+	for {
+		c, _, err := stdin.ReadRune()
+		if err == io.EOF || c == '\n' {
+			break
+		}
+		if err != nil {
+			fmt.Println("Error reading input")
+			os.Exit(1)
+		}
+		line = append(line, c)
+	}
+	inputBuffer.buffer = string(line)
 	bytesRead := len(inputBuffer.buffer)
 	if bytesRead <= 0 {
 		fmt.Println("Error reading input")
@@ -35,17 +109,31 @@ func readConsole(inputBuffer inputBuffer) inputBuffer {
 
 func main() {
 	inputBuffer := createInputBuffer()
+	statement := statement{0}
 	condition := true
 	for condition {
 		printConsole()
 		inputBuffer = readConsole(inputBuffer)
-
-		if inputBuffer.buffer == ".exit" {
-			fmt.Println("bye!")
-			os.Exit(0)
-		} else {
-			fmt.Printf("unrecognised command %v\n", inputBuffer.buffer)
+		if strings.Split(inputBuffer.buffer, "")[0] == "." {
+			switch doMetaCommands(inputBuffer) {
+			case metaCommandSuccess:
+				continue
+			case metaCommandUnrecognised:
+				fmt.Printf("unrecognised command %v\n", inputBuffer.buffer)
+				continue
+			}
 		}
 
+		switch prepareStatements(inputBuffer, &statement) {
+		case prepareSuccess:
+			break
+		case prepareUnrecognised:
+			fmt.Printf("Unrecognised keyword at the start of '%s'.\n", inputBuffer.buffer)
+			continue
+		}
+
+		executeStatement(&statement)
+		fmt.Println("Executed")
+
 	}
 }