140 lines
2.8 KiB
Go
140 lines
2.8 KiB
Go
package main
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import (
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"bufio"
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"fmt"
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"io"
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"os"
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"strings"
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)
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type metaCommandResults int
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type prepareResults int
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type statementType int
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const (
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metaCommandSuccess metaCommandResults = iota
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metaCommandUnrecognised
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)
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const (
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prepareSuccess prepareResults = iota
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prepareUnrecognised
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)
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const (
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statementSelect statementType = iota
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statementInsert
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)
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type inputBuffer struct {
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buffer string
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bufferLength int
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inputLength int
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}
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type statement struct {
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stype statementType
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}
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func doMetaCommands(inputBuffer inputBuffer) metaCommandResults {
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metacommand := metaCommandUnrecognised
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if inputBuffer.buffer == ".exit" {
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fmt.Println("bye!")
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os.Exit(0)
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} else {
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metacommand = metaCommandUnrecognised
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}
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return metacommand
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}
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func prepareStatements(inputBuffer inputBuffer, statement *statement) prepareResults {
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if strings.Split(inputBuffer.buffer, " ")[0] == "insert" {
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statement.stype = statementInsert
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return prepareSuccess
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}
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if strings.Split(inputBuffer.buffer, " ")[0] == "select" {
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statement.stype = statementSelect
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return prepareSuccess
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}
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return prepareUnrecognised
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}
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func executeStatement(statement *statement) {
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switch statement.stype {
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case statementInsert:
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fmt.Println("This is where the logic of insert statement should go")
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break
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case statementSelect:
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fmt.Println("This is where the logic of select statement should go")
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break
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}
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}
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func createInputBuffer() inputBuffer {
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newInputBuffer := inputBuffer{"", 0, 0}
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return newInputBuffer
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}
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func printConsole() {
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fmt.Print("godb > ")
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}
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func readConsole(inputBuffer inputBuffer) inputBuffer {
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var stdin *bufio.Reader
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var line []rune
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stdin = bufio.NewReader(os.Stdin)
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for {
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c, _, err := stdin.ReadRune()
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if err == io.EOF || c == '\n' {
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break
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}
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if err != nil {
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fmt.Println("Error reading input")
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os.Exit(1)
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}
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line = append(line, c)
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}
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inputBuffer.buffer = string(line)
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bytesRead := len(inputBuffer.buffer)
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if bytesRead <= 0 {
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fmt.Println("Error reading input")
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os.Exit(1)
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}
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inputBuffer.bufferLength = len(inputBuffer.buffer)
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inputBuffer.inputLength = bytesRead - 1
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return inputBuffer
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}
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func main() {
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inputBuffer := createInputBuffer()
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statement := statement{0}
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condition := true
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for condition {
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printConsole()
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inputBuffer = readConsole(inputBuffer)
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if strings.Split(inputBuffer.buffer, "")[0] == "." {
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switch doMetaCommands(inputBuffer) {
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case metaCommandSuccess:
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continue
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case metaCommandUnrecognised:
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fmt.Printf("unrecognised command %v\n", inputBuffer.buffer)
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continue
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}
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}
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switch prepareStatements(inputBuffer, &statement) {
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case prepareSuccess:
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break
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case prepareUnrecognised:
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fmt.Printf("Unrecognised keyword at the start of '%s'.\n", inputBuffer.buffer)
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continue
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}
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executeStatement(&statement)
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fmt.Println("Executed")
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}
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}
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