elves/elvish

// Command e3bc ("Elvish-editor-enhanced bc") is a wrapper for the bc command
// that uses Elvish's cli library for an enhanced CLI experience.
package main

import (
    "fmt"
    "io"
    "unicode"

    "src.elv.sh/pkg/cli"
    "src.elv.sh/pkg/cli/examples/e3bc/bc"
    "src.elv.sh/pkg/cli/modes"
    "src.elv.sh/pkg/cli/term"
    "src.elv.sh/pkg/cli/tk"
    "src.elv.sh/pkg/diag"
    "src.elv.sh/pkg/ui"
)

// A highlighter for bc code. Currently this just makes all digits green.
//
// TODO: Highlight more syntax of bc.
type highlighter struct{}

func (highlighter) Get(code string) (ui.Text, []ui.Text) {
    t := ui.Text{}
    for _, r := range code {
        var style ui.Styling
        if unicode.IsDigit(r) {
            style = ui.FgGreen
        }
        t = append(t, ui.T(string(r), style)...)
    }
    return t, nil
}

func (highlighter) LateUpdates() <-chan struct{} { return nil }

func main() {
    var app cli.App
    app = cli.NewApp(cli.AppSpec{
        Prompt:      cli.NewConstPrompt(ui.T("bc> ")),
        Highlighter: highlighter{},
        CodeAreaBindings: tk.MapBindings{
            term.K('D', ui.Ctrl): func(tk.Widget) { app.CommitEOF() },
            term.K(ui.Tab): func(w tk.Widget) {
                codearea := w.(tk.CodeArea)
                if codearea.CopyState().Buffer.Content != "" {
                    // Only complete with an empty buffer
                    return
                }
                w, err := modes.NewCompletion(app, modes.CompletionSpec{
                    Replace: diag.Ranging{From: 0, To: 0}, Items: candidates(),
                })
                if err == nil {
                    app.PushAddon(w)
                }
            },
        },
        GlobalBindings: tk.MapBindings{
            term.K('[', ui.Ctrl): func(tk.Widget) { app.PopAddon() },
        },
    })

    bc := bc.Start()
    defer bc.Quit()

    for {
        code, err := app.ReadCode()
        if err != nil {
            if err != io.EOF {
                fmt.Println("error:", err)
            }
            break
        }
        bc.Exec(code)
    }
}