package readline

/*
// IMPORTANT: choose one
#cgo LDFLAGS: -ledit
//#cgo LDFLAGS: -lreadline // NOTE: libreadline is GPL

// free()
#include <stdlib.h>
// readline()
#include <readline/readline.h>
// add_history()
#include <readline/history.h>
*/
import "C"

import (
    "errors"
    "unsafe"
    "strings"
    "io/ioutil"
    "os"
    "path/filepath"
    "fmt"
)

var HISTORY_FILE = ".mal-history"

var rl_history_loaded = false

func Readline(prompt string) (string, error) {
    history_path := filepath.Join(os.Getenv("HOME"), "/", HISTORY_FILE)

    if !rl_history_loaded {
        rl_history_loaded = true
        content, e := ioutil.ReadFile(history_path)
        if e != nil { return "", e }

        for _, add_line := range strings.Split(string(content), "\n") {
            if add_line == "" { continue }
            c_add_line := C.CString(add_line)
            C.add_history(c_add_line)
            C.free(unsafe.Pointer(c_add_line))
        }
    }


    c_prompt := C.CString(prompt)
    defer C.free(unsafe.Pointer(c_prompt))

    c_line := C.readline(c_prompt)
    defer C.free(unsafe.Pointer(c_line))
    line := C.GoString(c_line)

    if c_line == nil {
        return "", errors.New("C.readline call failed")
    }
    C.add_history(c_line)

    // append to file
    f, e := os.OpenFile(history_path, os.O_APPEND|os.O_WRONLY, 0600) 
    if e == nil {
        defer f.Close()

        _, e = f.WriteString(line+"\n")
        if e != nil { fmt.Printf("error writing to history") }
    }

    return line, nil
}