package backend

import (
	"crypto/rand"
	"fmt"
	"io"
	"math"
	"math/big"
	"os"
	"os/exec"
	"strings"
)

const extendedCharset = "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~"

// TargetIsFile TargetStatusCheck checks if the targetLocation is a file, directory, or is inaccessible
// failCondition: 0 = fail on inaccessible, 1 = fail on inaccessible/file, 2 = fail on inaccessible/directory
// returns: isFile, isAccessible
func TargetIsFile(targetLocation string, errorOnFail bool, failCondition uint8) (bool, bool) {
	targetInfo, err := os.Stat(targetLocation)
	if err != nil {
		if errorOnFail {
			fmt.Println(AnsiError + "Failed to access \"" + targetLocation + "\" - ensure it exists and has the correct permissions" + AnsiReset)
			os.Exit(1)
		} else {
			return false, false
		}
	}
	if targetInfo.IsDir() {
		if errorOnFail && failCondition == 2 {
			fmt.Println(AnsiError + "\"" + targetLocation + "\" is a directory" + AnsiReset)
			os.Exit(1)
		}
		return false, true
	} else {
		if errorOnFail && failCondition == 1 {
			fmt.Println(AnsiError + "\"" + targetLocation + "\" is a file" + AnsiReset)
			os.Exit(1)
		}
		return true, true
	}
}

// WriteEntry writes entryData to an encrypted file at targetLocation
func WriteEntry(targetLocation string, entryData []string) {
	encryptedBytes := EncryptGPG(entryData)
	err := os.WriteFile(targetLocation, encryptedBytes, 0600)
	if err != nil {
		fmt.Println(AnsiError + "Failed to write to file: " + err.Error() + AnsiReset)
		os.Exit(1)
	}
}

// writeToStdin writes a string to a command's stdin
func writeToStdin(cmd *exec.Cmd, input string) {
	stdin, _ := cmd.StdinPipe()
	go func() {
		defer stdin.Close()
		io.WriteString(stdin, input)
	}()
}

// CreateTempFile creates a temporary file and returns a pointer to it
func CreateTempFile() *os.File {
	tempFile, err := os.CreateTemp("", "*.markdown")
	if err != nil {
		fmt.Println(AnsiError + "Failed to create temporary file: " + err.Error() + AnsiReset)
		os.Exit(1)
	}
	return tempFile
}

// removeFile removes a file at targetLocation and does not error if the file does not exist
func removeFile(targetLocation string) {
	// remove existing config file
	err := os.Remove(targetLocation)
	if err != nil {
		// ignore error if file does not exist
		if !os.IsNotExist(err) {
			fmt.Println(AnsiError + "Failed to remove \"" + targetLocation + "\":" + err.Error() + AnsiReset)
		}
	}
}

// RemoveTrailingEmptyStrings removes empty strings from the end of a slice
func RemoveTrailingEmptyStrings(slice []string) []string {
	for i := len(slice) - 1; i >= 0; i-- {
		if slice[i] != "" {
			return slice[:i+1]
		}
	}
	return []string{}
}

// StringGen generates a random string of a specified length and complexity
// complexity: minimum percentage of special characters to be returned in the generated string (only impacts complex strings)
func StringGen(length int, complex bool, complexity float64) string {
	var actualSpecialChars int // track the number of special characters in the generated string
	var minSpecialChars int    // track the minimum number of special characters to accept

	charset := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789" // default character set used for all strings
	if complex {
		minSpecialChars = int(math.Round(float64(length) * complexity)) // determine minimum number of special characters to accept
		charset = charset + extendedCharset
	}

	// loop until a string of the desired complexity is generated
	for {
		// generate a random string
		result := make([]byte, length)
		for i := range result {
			val, _ := rand.Int(rand.Reader, big.NewInt(int64(len(charset))))
			result[i] = charset[val.Int64()]
		}

		// return early if the string is not complex
		if !complex {
			return string(result)
		}

		// count the number of special characters in the generated string
		for _, char := range string(result) {
			if strings.ContainsRune(extendedCharset, char) {
				actualSpecialChars++
			}
		}

		// return the generated string if it contains enough special characters
		if actualSpecialChars >= minSpecialChars {
			return string(result)
		}

		// reset special character counter
		fmt.Println("Regenerating string until desired complexity is achieved...")
		actualSpecialChars = 0
	}
}

// EntryIsNotEmpty iterates through entryData and returns true if any line is not empty
func EntryIsNotEmpty(entryData []string) bool {
	for _, line := range entryData {
		if line != "" {
			return true
		}
	}
	return false
}