/*
 * parser.c
 * Handles parsing of songs and playing of the parsed notes
 *
 *  Created on: Nov 25, 2025
 *      Author: sowgro
 */

#include <parser.h>
#include "endian_converters.h"
#include <stdint.h>
#include "endian_converters.h"
#include "hw8.h"
#include "activity4.h"
#include "systick.h"
#include "tone.h"

static track_t tracks[4];
static int nTracks;
static int startTime;
static song_info_t song_info;

/**
 * Prepare the parser to play the notes
 * Expected that parse_song() was called first
 */
void parser_play_init() {
	startTime = systick_get_count();
}

/**
 * Play any notes that are ready to be played
 * Should be called continuously in the play state
 * Expected that parse_song() was called first
 */
void parser_play_loop() {
	int curAbsTime = systick_get_count() - startTime;
	for (int i = 0; i < nTracks; i++) {
		note_event_t curEvent = tracks[i].events[tracks[i].curEventIndex];
		if (curEvent.abs_time >= curAbsTime) {
			switch (curEvent.ev_type) {
			case NOTE_OFF_EVENT:
				remove_tone(curEvent.key_number); break;
			case NOTE_ON_EVENT:
				add_tone(curEvent.key_number, curEvent.value); break;
			}
			tracks[i].curEventIndex++;
		}
	}
	play_tones();
}

/**
 * Parse a song and populate the static fields with its information
 * @param p_song a pointer to the current position in the song
 */
void parse_song(uint8_t *p_song) {
	header_t header;
	header = get_header(p_song);
	p_song += sizeof(header_t) - 2; // move pointer past header

	parse_song_info(p_song, &song_info);

	nTracks = header.ntrcks;
	for(int i = 0; i < nTracks; i++){
		p_song = parse_track(p_song, &tracks[i]);
	}
}

/**
 * Parse the track and populate the track parameter with its information
 * @param p_song a pointer to the current position in the song
 * @param track a pointer to a track to output to
 * @returns a pointer to the song after the track
 */
uint8_t *parse_track(uint8_t *p_song, track_t *track) {
	p_song += 4; // skip MTrk
	uint32_t MTrk_len = convert_to_uint32(p_song);
	p_song += 4;

	int curEvent = 0;
	uint32_t prev_abs_time = 0;

	for (uint8_t *p_end = p_song + MTrk_len; p_song != p_end; p_song++) {
		note_event_t note;

		parseDelay_result_t delay_result = parseDelay(p_song);
		uint32_t abs_time = prev_abs_time + delay_result.value;
		note.abs_time = abs_time;
		prev_abs_time = abs_time;
		p_song += delay_result.bytes_used;


		if (*p_song >> 4 == 0b1000) {
			note.ev_type = NOTE_OFF_EVENT;
		} else if (*p_song >> 4 == 0b1001) {
			note.ev_type = NOTE_ON_EVENT;
		} else if (*p_song >> 4 == 0b1010) {
			note.ev_type = KEY_PRESSURE;
		} else {
			continue;
		}

//		size_t channelNumber = *p_song && 0b00001111;
		p_song++;

		note.key_number = *p_song;
		p_song++;

		note.value = *p_song;
		p_song++;

		track->events[curEvent++] = note;
	}
	track->nEvents = curEvent;
	track->curEventIndex = 0;

	return p_song;
}

/**
 * Parses the track information
 * @param p_song a pointer to the current position in the song
 * @param ret the output parameter
 * @returns a pointer to the song after the track info
 */
uint8_t *parse_song_info(uint8_t *p_song, song_info_t *ret) {
	ret->copyright = 0;
	ret->tempo = 0;
	ret->title = 0;

	p_song += 4; // move past MTrk label
	uint32_t MTrk_len = convert_to_uint32(p_song); // read in size of MTrk
	p_song += sizeof(MTrk_len);

	for (uint8_t *p_end = p_song + MTrk_len; p_song != p_end; p_song++) {
		// FF 02 - copyright
		if (convert_to_uint16(p_song) == 0xFF02) {
			p_song += sizeof(uint16_t);
			uint8_t ev_len = *(uint8_t *) p_song;
			p_song += sizeof(ev_len);
			ret->copyright = (char *) p_song;
			ret->copyright[ev_len] = 0;
		}

		// FF 03 - title
		if (convert_to_uint16(p_song) == 0xFF03) {
			p_song += sizeof(uint16_t);
			uint8_t ev_len = *(uint8_t *) p_song;
			p_song += sizeof(ev_len);
			ret->title = (char *) p_song;
			ret->title[ev_len] = 0;
		}

		// FF 51 - tempo
		if (convert_to_uint16(p_song) == 0xFF51) {
			p_song += sizeof(uint16_t);
			p_song += sizeof(uint8_t); // skip length, always 03
			ret->tempo = convert_to_uint24(p_song);
		}
	}

	return p_song;
}

/**
 * An accessor for other files to get the song information
 */
song_info_t parser_get_song_info() {
	return song_info;
}