package zygo

import (
	"errors"
	"fmt"
	"strings"
)

func ConcatStr(str *SexpStr, rest []Sexp) (*SexpStr, error) {
	res := &SexpStr{S: str.S}
	for i, x := range rest {
		switch t := x.(type) {
		case *SexpStr:
			res.S += t.S
		case *SexpChar:
			res.S += string(t.Val)
		default:
			return &SexpStr{}, fmt.Errorf("ConcatStr error: %d-th argument (0-based) is "+
				"not a string (was %T)", i, t)
		}
	}

	return res, nil
}

func AppendStr(str *SexpStr, expr Sexp) (*SexpStr, error) {
	var chr *SexpChar
	switch t := expr.(type) {
	case *SexpChar:
		chr = t
	case *SexpStr:
		return &SexpStr{S: str.S + t.S}, nil
	default:
		return &SexpStr{}, errors.New("second argument is not a char")
	}

	return &SexpStr{S: str.S + string(chr.Val)}, nil
}

func StringUtilFunction(env *Zlisp, name string, args []Sexp) (Sexp, error) {
	if len(args) != 1 {
		return SexpNull, WrongNargs
	}
	var s string
	switch str := args[0].(type) {
	case *SexpStr:
		s = str.S
	default:
		return SexpNull, fmt.Errorf("string required, got %T", s)
	}

	switch name {
	case "chomp":
		n := len(s)
		if n > 0 && s[n-1] == '\n' {
			return &SexpStr{S: s[:n-1]}, nil
		}
		return &SexpStr{S: s}, nil
	case "trim":
		return &SexpStr{S: strings.TrimSpace(s)}, nil
	}
	return SexpNull, fmt.Errorf("unrecognized command '%s'", name)
}