// Copyright © 2014 Steve Francia <spf@spf13.com>.
//
// Licensed under the Simple Public License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://opensource.org/licenses/Simple-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package helpers

import (
	"bytes"
	"crypto/md5"
	"encoding/hex"
	"errors"
	"fmt"
	bp "github.com/spf13/hugo/bufferpool"
	"github.com/spf13/viper"
	"io"
	"net"
	"path/filepath"
	"reflect"
	"strings"
)

// Filepath separator defined by os.Separator.
const FilePathSeparator = string(filepath.Separator)

func FindAvailablePort() (*net.TCPAddr, error) {
	l, err := net.Listen("tcp", ":0")
	if err == nil {
		defer l.Close()
		addr := l.Addr()
		if a, ok := addr.(*net.TCPAddr); ok {
			return a, nil
		}
		return nil, fmt.Errorf("Unable to obtain a valid tcp port. %v", addr)
	}
	return nil, err
}

// InStringArray checks if a string is an element of a slice of strings
// and returns a boolean value.
func InStringArray(arr []string, el string) bool {
	for _, v := range arr {
		if v == el {
			return true
		}
	}
	return false
}

// GuessType attempts to guess the type of file from a given string.
func GuessType(in string) string {
	switch strings.ToLower(in) {
	case "md", "markdown", "mdown":
		return "markdown"
	case "rst":
		return "rst"
	case "html", "htm":
		return "html"
	}

	return "unknown"
}

// ReaderToBytes takes an io.Reader argument, reads from it
// and returns bytes.
func ReaderToBytes(lines io.Reader) []byte {
	b := bp.GetBuffer()
	defer bp.PutBuffer(b)

	b.ReadFrom(lines)

	bc := make([]byte, b.Len(), b.Len())
	copy(bc, b.Bytes())
	return bc
}

// ReaderToString is the same as ReaderToBytes, but returns a string.
func ReaderToString(lines io.Reader) string {
	b := bp.GetBuffer()
	defer bp.PutBuffer(b)
	b.ReadFrom(lines)
	return b.String()
}

// StringToReader does the opposite of ReaderToString.
func StringToReader(in string) io.Reader {
	return strings.NewReader(in)
}

// BytesToReader does the opposite of ReaderToBytes.
func BytesToReader(in []byte) io.Reader {
	return bytes.NewReader(in)
}

func ThemeSet() bool {
	return viper.GetString("theme") != ""
}

// SliceToLower goes through the source slice and lowers all values.
func SliceToLower(s []string) []string {
	if s == nil {
		return nil
	}

	l := make([]string, len(s))
	for i, v := range s {
		l[i] = strings.ToLower(v)
	}

	return l
}

// Md5String takes a string and returns its MD5 hash.
func Md5String(f string) string {
	h := md5.New()
	h.Write([]byte(f))
	return hex.EncodeToString(h.Sum([]byte{}))
}

// DoArithmetic performs arithmetic operations (+,-,*,/) using reflection to
// determine the type of the two terms.
func DoArithmetic(a, b interface{}, op rune) (interface{}, error) {
	av := reflect.ValueOf(a)
	bv := reflect.ValueOf(b)
	var ai, bi int64
	var af, bf float64
	var au, bu uint64
	switch av.Kind() {
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		ai = av.Int()
		switch bv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			bi = bv.Int()
		case reflect.Float32, reflect.Float64:
			af = float64(ai) // may overflow
			ai = 0
			bf = bv.Float()
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			bu = bv.Uint()
			if ai >= 0 {
				au = uint64(ai)
				ai = 0
			} else {
				bi = int64(bu) // may overflow
				bu = 0
			}
		default:
			return nil, errors.New("Can't apply the operator to the values")
		}
	case reflect.Float32, reflect.Float64:
		af = av.Float()
		switch bv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			bf = float64(bv.Int()) // may overflow
		case reflect.Float32, reflect.Float64:
			bf = bv.Float()
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			bf = float64(bv.Uint()) // may overflow
		default:
			return nil, errors.New("Can't apply the operator to the values")
		}
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		au = av.Uint()
		switch bv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			bi = bv.Int()
			if bi >= 0 {
				bu = uint64(bi)
				bi = 0
			} else {
				ai = int64(au) // may overflow
				au = 0
			}
		case reflect.Float32, reflect.Float64:
			af = float64(au) // may overflow
			au = 0
			bf = bv.Float()
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			bu = bv.Uint()
		default:
			return nil, errors.New("Can't apply the operator to the values")
		}
	case reflect.String:
		as := av.String()
		if bv.Kind() == reflect.String && op == '+' {
			bs := bv.String()
			return as + bs, nil
		} else {
			return nil, errors.New("Can't apply the operator to the values")
		}
	default:
		return nil, errors.New("Can't apply the operator to the values")
	}

	switch op {
	case '+':
		if ai != 0 || bi != 0 {
			return ai + bi, nil
		} else if af != 0 || bf != 0 {
			return af + bf, nil
		} else if au != 0 || bu != 0 {
			return au + bu, nil
		} else {
			return 0, nil
		}
	case '-':
		if ai != 0 || bi != 0 {
			return ai - bi, nil
		} else if af != 0 || bf != 0 {
			return af - bf, nil
		} else if au != 0 || bu != 0 {
			return au - bu, nil
		} else {
			return 0, nil
		}
	case '*':
		if ai != 0 || bi != 0 {
			return ai * bi, nil
		} else if af != 0 || bf != 0 {
			return af * bf, nil
		} else if au != 0 || bu != 0 {
			return au * bu, nil
		} else {
			return 0, nil
		}
	case '/':
		if bi != 0 {
			return ai / bi, nil
		} else if bf != 0 {
			return af / bf, nil
		} else if bu != 0 {
			return au / bu, nil
		} else {
			return nil, errors.New("Can't divide the value by 0")
		}
	default:
		return nil, errors.New("There is no such an operation")
	}
}