feat: split into code for buffer and vm

internals/buffer/buffer.go

@@ -0,0 +1,30 @@
+package buffer
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+)
+
+type InputBuffer struct {
+	Buffer string
+	Reader *bufio.Reader
+}
+
+func NewInputBuffer() *InputBuffer {
+	return &InputBuffer{
+		Buffer: "",
+		Reader: bufio.NewReader(os.Stdin),
+	}
+}
+
+func (inputBuffer *InputBuffer) ReadConsole() {
+	line, err := inputBuffer.Reader.ReadString('\n')
+	if err != nil && err != io.EOF {
+		fmt.Println("Error reading input", err)
+		os.Exit(1)
+	}
+	inputBuffer.Buffer = strings.TrimSpace(line)
+}

internals/repl/repl.go

@@ -1,34 +1,44 @@
 package repl
 
 import (
-	"bufio"
 	"fmt"
-	"io"
-	"os"
 	"strings"
+
+	. "godb/internals/buffer"
+	. "godb/internals/vm"
 )
 
-type InputBuffer struct {
-	Buffer string
-	Reader *bufio.Reader
-}
-
-func NewInputBuffer() *InputBuffer {
-	return &InputBuffer{
-		Buffer: "",
-		Reader: bufio.NewReader(os.Stdin),
-	}
-}
-
 func PrintConsole() {
 	fmt.Print("godb > ")
 }
 
-func (inputBuffer *InputBuffer) ReadConsole() {
-	line, err := inputBuffer.Reader.ReadString('\n')
-	if err != nil && err != io.EOF {
-		fmt.Println("Error reading input", err)
-		os.Exit(1)
+func Run() {
+
+	inputBuffer := NewInputBuffer()
+	statement := NewStatement()
+	for {
+		PrintConsole()
+		inputBuffer.ReadConsole()
+		if len(inputBuffer.Buffer) > 0 && strings.HasPrefix(inputBuffer.Buffer, ".") {
+			switch DoMetaCommands(inputBuffer) {
+			case MetaCommandSuccess:
+				continue
+			case MetaCommandUnrecognised:
+				fmt.Printf("unrecognised command %v\n", inputBuffer.Buffer)
+				continue
+			}
+		}
+
+		switch statement.PrepareStatements(inputBuffer) {
+		case PrepareSuccess:
+			//todo
+		case PrepareUnrecognised:
+			fmt.Printf("Unrecognised keyword at the start of '%s'.\n", inputBuffer.Buffer)
+			continue
+		}
+
+		statement.ExecuteStatement()
+		fmt.Println("Executed")
+
 	}
-	inputBuffer.Buffer = strings.TrimSpace(line)
 }

internals/vm/vm.go

@@ -0,0 +1,86 @@
+package vm
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	. "godb/internals/buffer"
+)
+
+type MetaCommandResults int
+
+const (
+	MetaCommandSuccess MetaCommandResults = iota
+	MetaCommandUnrecognised
+)
+
+type PrepareResults int
+
+const (
+	PrepareSuccess PrepareResults = iota
+	PrepareUnrecognised
+	PrepareSyntaxError
+)
+
+type statementType int
+
+const (
+	StatementSelect statementType = iota
+	StatementInsert
+)
+
+type row struct {
+	id       uint
+	username string
+	email    string
+}
+
+type Statement struct {
+	stype statementType
+	row   row
+}
+
+func NewStatement() *Statement {
+	return &Statement{0, row{0, "", ""}}
+}
+
+func DoMetaCommands(inputBuffer *InputBuffer) MetaCommandResults {
+	metacommand := MetaCommandUnrecognised
+	if inputBuffer.Buffer == ".exit" {
+		fmt.Println("bye!")
+		os.Exit(0)
+	} else {
+		metacommand = MetaCommandUnrecognised
+	}
+	return metacommand
+}
+
+func (statement *Statement) PrepareStatements(inputBuffer *InputBuffer) PrepareResults {
+	if strings.HasPrefix(inputBuffer.Buffer, "insert") {
+		argsAssigned, err := fmt.Sscanf(inputBuffer.Buffer, "insert %d %s %s", &statement.row.id, &statement.row.username, &statement.row.email)
+		if err != nil {
+			fmt.Println("error parsing insert statement")
+			fmt.Println(err.Error())
+		}
+		if argsAssigned > 3 {
+			return PrepareSyntaxError
+		}
+		statement.stype = StatementInsert
+		return PrepareSuccess
+	}
+	if strings.HasPrefix(inputBuffer.Buffer, "select") {
+		statement.stype = StatementSelect
+		return PrepareSuccess
+	}
+	return PrepareUnrecognised
+}
+
+func (statement *Statement) ExecuteStatement() {
+	switch statement.stype {
+	case StatementInsert:
+		fmt.Println("This is where the logic of insert statement should go")
+	case StatementSelect:
+		fmt.Println("This is where the logic of select statement should go")
+	}
+}