compiler-in-go/pkg/repl/repl.go

package repl

import (
	"bufio"
	"fmt"
	"io"

	"code.jmug.me/jmug/compiler-in-go/pkg/evaluator"
	"code.jmug.me/jmug/compiler-in-go/pkg/lexer"
	"code.jmug.me/jmug/compiler-in-go/pkg/object"
	"code.jmug.me/jmug/compiler-in-go/pkg/parser"
)

const PROMPT = ">> "

func Start(in io.Reader, out io.Writer) {
	scanner := bufio.NewScanner(in)
	env := object.NewEnvironment()
	for {
		fmt.Fprint(out, PROMPT)
		if !scanner.Scan() {
			return
		}
		l := lexer.New(scanner.Text())
		p := parser.New(l)
		program := p.ParseProgram()
		if len(p.Errors()) != 0 {
			printParserErrors(out, p.Errors())
			continue
		}
		res := evaluator.Eval(program, env)
		if res != nil {
			io.WriteString(out, res.Inspect())
			io.WriteString(out, "\n")
		}
	}
}

const MONKEY_FACE = `            __,__
   .--.  .-"     "-.  .--.
  / .. \/  .-. .-.  \/ .. \
 | |  '|  /   Y   \  |'  | |
 | \   \  \ 0 | 0 /  /   / |
  \ '- ,\.-"""""""-./, -' /
   ''-' /_   ^ ^   _\ '-''
       |  \._   _./  |
       \   \ '~' /   /
        '._ '-=-' _.'
           '-----'
`

func printParserErrors(out io.Writer, errors []string) {
	io.WriteString(out, MONKEY_FACE)
	io.WriteString(out, "Woops! We ran into some monkey business here!\n")
	io.WriteString(out, " parser errors:\n")
	for _, msg := range errors {
		io.WriteString(out, "\t"+msg+"\n")
	}
}