/**
 * @author Tyler Beckman (tyler_beckman@mines.edu)
 * @brief A3 - A program to parse a text input and analyze it for statistics
 * based on word and letter frequency, and then output them to a user-specified
 * file. It assumes text is only alphabetical + spaces + the punctuation
 * contained within main.cpp. In addition, the list of word counts is sorted
 * using a recursive MSD radix sort before being outputted into the specified
 * file.
 * @version 1
 * @date 2024-10-10
 *
 * Resources used:
 * For the general program (not sorting), I utilized all autocomplete and
 * cppreference to find the detailed reference of functions I needed to use. For
 * implementing radix sort I primarily used
 * https://en.wikipedia.org/wiki/Radix_sort#Most_significant_digit,_forward_recursive
 * and a lot of trial and error. The sorting part is also VERY commented to make
 * sure I knew exactly what I was doing at each point and why I was doing it.
 */

#include "OutputProcessor.h"

#include <fstream>
#include <iomanip>
#include <iostream>
#include <optional>
#include <ostream>
#include <string>
#include <vector>

#include <cstdint>

/**
 * @brief Recursively most significant digit radix sorts a vector of indexes,
 * based on the alphabetical value of a vector of strings. The returned vector
 * is the same index vector but re-arranged to show where the elements in the
 * string vector should be placed.
 *
 * @param INDEXES The vector of indexes to sort
 * @param VECTOR_TO_SORT The string vector to base the sort off of. This will
 * not be modified, and is only used to decide where an index in the other
 * vector gets placed during sort.
 * @param DEPTH The current sort depth, should be 0 or not passed if called from
 * outside of this function. This controls which character of strings is
 * inspected during sort.
 */
void radixSortIndexes(std::vector<size_t> &INDEXES,
					  const std::vector<std::string> &VECTOR_TO_SORT,
					  const unsigned int DEPTH = 0) {
	// Construct 26 buckets, where 0 = A, 1 = B, 2 = C, ..., 25 = Z
	std::vector<std::vector<size_t>> buckets(26);
	// Another "bucket" for words that have already been completely sorted, as
	// they have no character to check at position `DEPTH`
	std::optional<size_t> alreadySorted = std::nullopt;

	// Pass over each index, bucketing based on the character corresponding to
	// the current depth
	for (size_t i = 0; i < INDEXES.size(); i++) {
		const size_t INDEX_TO_SORT = INDEXES.at(i);
		const std::string &WORD = VECTOR_TO_SORT.at(INDEX_TO_SORT);

		// Check if the word has any more characters to bucket. If it doesn't,
		// place it in the special `alreadySorted` bucket. If it does, add it to
		// the correct bucket for the current depth.
		if (WORD.length() == DEPTH) {
			alreadySorted = INDEX_TO_SORT;
		} else {
			buckets.at(WORD.at(DEPTH) - 65).push_back(INDEX_TO_SORT);
		}
	}

	// Recursively apply bucket sort to each bucket unless it is already
	// completely sorted (has no elements or only has one). With this we cascade
	// the bucketing as far as is necessary, flattening after we have reached a
	// depth at which there is no more to bucket (each bucket has 0 or 1
	// elements)
	for (size_t i = 0; i < buckets.size(); i++) {
		std::vector<size_t> &bucket = buckets.at(i);

		if (bucket.size() > 1) {
			radixSortIndexes(bucket, VECTOR_TO_SORT, DEPTH + 1);
		}
	}

	// Flatten the buckets at the current stage. We first add the
	// `alreadySorted` value (less characters should go before more characters),
	// and then append each item from each bucket individually.
	std::vector<size_t> flattenedBucket;
	if (alreadySorted.has_value()) {
		flattenedBucket.push_back(alreadySorted.value());
	}
	for (size_t i = 0; i < buckets.size(); i++) {
		flattenedBucket.insert(flattenedBucket.end(), buckets.at(i).begin(),
							   buckets.at(i).end());
	}

	// Finally, replace the indexes with the sorted result
	INDEXES = flattenedBucket;
}

/**
 * @brief Sorts the `words` vector (and `wordCounts` alongside) alphabetically
 * using a most significant digit radix sort.
 *
 * @param words The list of words to sort alphabetically
 * @param wordCounts The vector of word counts aligned to the `words` vector,
 * which will be be adjusted based on the result of sorting `words`
 */
void radixSort(std::vector<std::string> &words,
			   std::vector<unsigned int> &wordCounts) {
	// Create a vector of indexes the size of the amount of words we have. This
	// is the vector that will actually be returned sorted in the end, where
	// each element of this vector `i` is set to the index of `words` or
	// `wordCounts` that belongs in position `i` when sorted. By doing this, we
	// avoid having to try and pass around both the words and their
	// corresponding counts throughout the sort, and can just re-assemble the
	// vectors at the end.
	std::vector<size_t> indexVector(words.size());
	for (size_t i = 0; i < words.size(); i++) {
		indexVector.push_back(i);
	}

	// Sort the `indexVector` vector against the `words` vector, starting with
	// depth 0 (the left-most character)
	radixSortIndexes(indexVector, words);

	// Reconstruct the `words` and `wordCounts` vectors from the list of
	// indexes, and replace the originals with the new ones
	std::vector<std::string> sortedWords;
	std::vector<unsigned int> sortedWordCounts;

	for (size_t i = 0; i < indexVector.size(); i++) {
		sortedWords.push_back(words.at(indexVector.at(i)));
		sortedWordCounts.push_back(wordCounts.at(indexVector.at(i)));
	}

	words = sortedWords;
	wordCounts = sortedWordCounts;
}

OutputProcessor::OutputProcessor() {
	_fileOut = std::ofstream();
	_allWords = std::vector<std::string>();
	_uniqueWords = std::vector<std::string>();
	_letterCounts = std::vector<unsigned int>(26, 0);
	_wordCounts = std::vector<unsigned int>();
	_totalLetterCount = 0;
	_totalWordCount = 0;
}

void OutputProcessor::analyzeWords(std::vector<std::string> allWords,
								   const std::string PUNCTUATION) {
	// Iterate over all words, processing incrementally
	for (size_t wordIdx = 0; wordIdx < allWords.size(); wordIdx++) {
		std::string &word = allWords.at(wordIdx);

		// Remove punctuation from word
		size_t punctuationIdx = 0;
		while ((punctuationIdx = word.find_first_of(PUNCTUATION)) !=
			   std::string::npos) {
			word.erase(punctuationIdx, 1);
		}

		// Save word internally
		_allWords.push_back(word);

		// Check all unique words for a match, and if so increment the count
		bool foundUnique = false;
		size_t uniqueWordIdx;
		for (uniqueWordIdx = 0; uniqueWordIdx < _uniqueWords.size();
			 uniqueWordIdx++) {
			if (_uniqueWords.at(uniqueWordIdx) == word) {
				foundUnique = true;
				break;
			}
		}
		// If no unique word exists, add it to both vectors
		if (!foundUnique) {
			_uniqueWords.push_back(word);
			_wordCounts.push_back(1);
		} else {
			_wordCounts.at(uniqueWordIdx)++;
		}

		// Add letter count for each letter in the word
		for (size_t letterIdx = 0; letterIdx < word.length(); letterIdx++) {
			char letter = word.at(letterIdx);
			// Normalize to uppercase
			if (letter >= 'a' && letter <= 'z') {
				letter -= 97;
			} else {
				if (letter >= 'A' && letter <= 'Z') {
					letter -= 65;
				} else {
					continue;
				}
			}
			// Subtracting an uppercase letter by 65 creates its alphabetical
			// index
			_letterCounts.at(letter)++;
		}

		// Sum total letter count
		_totalLetterCount += word.length();

		// Increment total word count
		_totalWordCount++;
	}

	radixSort(_uniqueWords, _wordCounts);
}

bool OutputProcessor::openStream() {
	std::string file;
	std::cout << "What is the name of the file you would like to write to? ";
	std::cin >> file;

	if (std::cin.fail()) {
		std::cerr << "Invalid file input" << std::endl;
		return false;
	}

	_fileOut.open(file);
	if (_fileOut.fail()) {
		std::cerr << "Unable to open file, does it exist?" << std::endl;
		return false;
	}

	return true;
}

void OutputProcessor::closeStream() { _fileOut.close(); }

void OutputProcessor::write() {
	// Calculate longest word length, longest number length, most common word,
	// and least common word for later use in one pass for efficiency
	size_t longestWordLength = 0;

	size_t mostCommonWordIdx = 0;
	size_t leastCommonWordIdx = 0;

	for (size_t uniqueWordIdx = 0; uniqueWordIdx < _uniqueWords.size();
		 uniqueWordIdx++) {
		std::string &uniqueWord = _uniqueWords.at(uniqueWordIdx);
		unsigned long wordCount = _wordCounts.at(uniqueWordIdx);

		if (uniqueWord.length() > longestWordLength) {
			longestWordLength = uniqueWord.length();
		}

		// Equality can be ignored here because we want the word that was
		// encountered first, so any subsequent extremes can be ignored
		if (wordCount < _wordCounts.at(leastCommonWordIdx)) {
			leastCommonWordIdx = uniqueWordIdx;
		} else {
			if (wordCount > _wordCounts.at(mostCommonWordIdx)) {
				mostCommonWordIdx = uniqueWordIdx;
			}
		}
	}

	_fileOut << "Read in " << _totalWordCount << " words" << std::endl;
	_fileOut << "Encountered " << _uniqueWords.size() << " unique words"
			 << std::endl;

	// Print out each unique word and how often it happened
	const size_t MOST_COMMON_WORD_COUNT_LENGTH =
		std::to_string(_wordCounts.at(mostCommonWordIdx)).length();
	for (size_t uniqueWordIdx = 0; uniqueWordIdx < _uniqueWords.size();
		 uniqueWordIdx++) {
		_fileOut << std::setw(longestWordLength) << std::left
				 << _uniqueWords.at(uniqueWordIdx) << " : "
				 << std::setw(MOST_COMMON_WORD_COUNT_LENGTH) << std::right
				 << _wordCounts.at(uniqueWordIdx) << std::endl;
	}

	// Print the most and least common word
	const std::string &MOST_COMMON_WORD = _uniqueWords.at(mostCommonWordIdx);
	const std::string &LEAST_COMMON_WORD = _uniqueWords.at(leastCommonWordIdx);
	size_t longerFrequentWordLength =
		MOST_COMMON_WORD.length() > LEAST_COMMON_WORD.length()
			? MOST_COMMON_WORD.length()
			: LEAST_COMMON_WORD.length();
	size_t mostFrequentWordCountLength =
		std::to_string(_wordCounts.at(mostCommonWordIdx)).length();

	_fileOut << " Most Frequent Word: " << std::setw(longerFrequentWordLength)
			 << std::left << MOST_COMMON_WORD << " " << std::right
			 << std::setw(mostFrequentWordCountLength)
			 << _wordCounts.at(mostCommonWordIdx) << " (" << std::setw(7)
			 << std::fixed << std::setprecision(3) << std::right
			 << (float)_wordCounts.at(mostCommonWordIdx) / _totalWordCount * 100
			 << "%)" << std::endl;
	_fileOut << "Least Frequent Word: " << std::setw(longerFrequentWordLength)
			 << std::left << LEAST_COMMON_WORD << " " << std::right
			 << std::setw(mostFrequentWordCountLength)
			 << _wordCounts.at(leastCommonWordIdx) << " (" << std::setw(7)
			 << std::fixed << std::setprecision(3) << std::right
			 << (float)_wordCounts.at(leastCommonWordIdx) / _totalWordCount *
					100
			 << "%)" << std::endl;

	// Calculate the most and least common letters to display
	uint8_t mostCommonLetterIdx = 0;
	uint8_t leastCommonLetterIdx = 0;

	for (size_t letterIdx = 0; letterIdx < 26; letterIdx++) {
		// Here not using "or equals" means the letters later alphabetically get
		// ignored if they occur the same amount
		if (_letterCounts.at(letterIdx) <
			_letterCounts.at(leastCommonLetterIdx)) {
			leastCommonLetterIdx = letterIdx;
		} else {
			if (_letterCounts.at(letterIdx) >
				_letterCounts.at(mostCommonLetterIdx)) {
				mostCommonLetterIdx = letterIdx;
			}
		}
	}

	// Print out each letter along with the amount of times it occurs
	const size_t MOST_COMMON_LETTER_COUNT_LENGTH =
		std::to_string(_letterCounts.at(mostCommonLetterIdx)).length();
	for (size_t letterIdx = 0; letterIdx < 26; letterIdx++) {
		_fileOut << (char)(letterIdx + 65) << ": "
				 << std::setw(MOST_COMMON_LETTER_COUNT_LENGTH) << std::right
				 << _letterCounts.at(letterIdx) << std::endl;
	}

	// Print out the most and least common letters in total
	_fileOut << " Most Frequent Letter: " << (char)(mostCommonLetterIdx + 65)
			 << " " << std::setw(MOST_COMMON_LETTER_COUNT_LENGTH) << std::right
			 << _letterCounts.at(mostCommonLetterIdx) << " (" << std::setw(7)
			 << std::fixed << std::setprecision(3)
			 << ((float)_letterCounts.at(mostCommonLetterIdx) /
				 _totalLetterCount * 100)
			 << "%)" << std::endl;
	_fileOut << "Least Frequent Letter: " << (char)(leastCommonLetterIdx + 65)
			 << " " << std::setw(MOST_COMMON_LETTER_COUNT_LENGTH) << std::right
			 << _letterCounts.at(leastCommonLetterIdx) << " (" << std::setw(7)
			 << std::fixed << std::setprecision(3)
			 << ((float)_letterCounts.at(leastCommonLetterIdx) /
				 _totalLetterCount * 100)
			 << "%)" << std::endl;
}