package main

import (
	"fmt"
	"math/rand/v2"
	"os"
	"path/filepath"
)

func fillSliceWithASCII(slice []byte) {
	const asciiMin = 16
	const asciiMax = 150

	for i := range slice {
		slice[i] = byte(rand.Int32N(asciiMax-asciiMin+1) + asciiMin)
	}
}

func glitchImage(inputFile string, outputFile string, shitSize int64, iterations int64) error {
	outputFilePath := filepath.Join("output", outputFile)

	// Open the source file for reading
	source, err := os.Open(inputFile)
	check(err, "failed to open source file: %w")
	defer source.Close()

	// Create a new file for writing the glitched copy
	destination, err := os.Create(outputFilePath)
	check(err, "failed to create output file: %w")
	defer destination.Close()

	// Copy the contents of the source file to the destination
	_, err = destination.ReadFrom(source)
	check(err, "failed to copy file contents: %w")

	// Get the Stat() of the destination file
	fileInfo, err := destination.Stat()
	check(err, "failed to get file info: %w")

	// Get the size of the destination file
	fileSize := fileInfo.Size()
	if fileSize == 0 {
		fmt.Println("Cannot glitch file with size of zero bytes!")
		return fmt.Errorf("input file is zero bytes")
	}

	// Generate a random offset within the file
	var i int64
	for i = 0; i < iterations; i++ {
		offset := rand.Int64N(fileSize)

		// Seek to the random offset in the destination file
		_, err = destination.Seek(offset, 0)
		check(err, "failed to seek to random offset: %w")

		// Generate random data and write it in
		shit := make([]byte, shitSize)
		fillSliceWithASCII(shit)
		_, err = destination.Write(shit)
		check(err, "failed to write shit data: %w")

	}
	return nil
}

func copyImage(inputFile string, outputFile string) error {
	// Prepend the "output" directory to the output file
	outputFilePath := filepath.Join("output", outputFile)

	// Open the source file for reading
	source, err := os.Open(inputFile)
	check(err, "failed to open source file: %w")
	defer source.Close()

	// Create a new file for writing the copy
	destination, err := os.Create(outputFilePath)
	check(err, "failed to create output file: %w")
	defer destination.Close()

	// Copy the contents of the source file to the destination
	_, err = destination.ReadFrom(source)
	check(err, "failed to copy file contents: %w")

	// no errors
	return nil
}

func generateGlitchedSequence(inputFile string, fileExt string, totalImages int, shitSize int64, iterations int64, chanceToRandom int32) error {
	for i := 1; i <= totalImages; i++ {
		outputFileName := fmt.Sprintf("img_glitched_%d.%s", i, fileExt)

		if rand.Int32N(100) < chanceToRandom {
			// Glitched image
			err := glitchImage(inputFile, outputFileName, shitSize, iterations)
			if err != nil {
				return fmt.Errorf("Cannot glitch image")
			}
		} else {
			// Normal image
			err := copyImage(inputFile, outputFileName)
			if err != nil {
				return fmt.Errorf("Cannot glitch image")
			}
		}
	}
	// no errors
	return nil
}