sjansen/mecha

package main

import (
    "fmt"
    "io"
    "strings"

    "github.com/chzyer/readline"
    "go.starlark.net/starlark"
    "go.starlark.net/syntax"
)

const ps1 = "> "
const ps2 = ": "

var completer = readline.NewPrefixCompleter(
    readline.PcItem("print("),
)

func main() {
    opts := &syntax.FileOptions{
        Set: true,
    }

    l, err := readline.NewEx(&readline.Config{
        AutoComplete:           completer,
        DisableAutoSaveHistory: true,
        EOFPrompt:              "exit",
        HistoryFile:            "/tmp/readline.tmp",
        InterruptPrompt:        "^C",
        Prompt:                 ps1,
    })
    if err != nil {
        panic(err)
    }
    defer l.Close()

    predeclared := starlark.StringDict{}
    thread := &starlark.Thread{}

    var lines []string
LOOP:
    for {
        line, err := l.Readline()
        switch {
        case err == readline.ErrInterrupt:
            if len(line) == 0 {
                break LOOP
            } else {
                continue
            }
        case err == io.EOF:
            break LOOP
        case line == "exit":
            break LOOP
        }

        lines = append(lines, line)
        switch {
        case strings.HasPrefix(line, " "):
            continue
        case strings.HasSuffix(line, ":"):
            l.SetPrompt(ps2)
            continue
        }

        buffer := strings.Join(lines, "\n")
        lines = lines[:0]
        l.SetPrompt(ps1)
        l.SaveHistory(buffer)

        _, err = syntax.ParseExpr("<stdin>", line, 0)
        if err != nil {
            globals, err := starlark.ExecFileOptions(opts, thread, "<stdin>", buffer, predeclared)
            if err != nil {
                fmt.Println(err)
            } else {
                for k, v := range globals {
                    predeclared[k] = v
                }
            }
        } else {
            if v, err := starlark.EvalOptions(opts, thread, "<stdin>", buffer, predeclared); err != nil {
                fmt.Println(err.Error())
            } else {
                fmt.Println(v.String())
            }
        }
    }
}