/*
 * Copyright (c) 2021 Raspberry Pi (Trading) Ltd.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <stdio.h>

#include "pico.h"
#include "pico/stdlib.h"
#include "pico/multicore.h"
#include "pico/scanvideo.h"
#include "pico/scanvideo/composable_scanline.h"
#include "pico/sync.h"

#define vga_mode vga_mode_320x240_60

void core1_func();

// Simple color bar program, which draws 7 colored bars: red, green, yellow, blow, magenta, cyan, white
// Can be used to check resister DAC correctness.
//
// Note this program also demonstrates running video on core 1, leaving core 0 free. It supports
// user input over USB or UART stdin, although all it does with it is invert the colors when you press SPACE

static semaphore_t video_initted;
static bool invert;

int main(void) {
    stdio_init_all();

    // create a semaphore to be posted when video init is complete
    sem_init(&video_initted, 0, 1);

    // launch all the video on core 1, so it isn't affected by USB handling on core 0
    multicore_launch_core1(core1_func);

    // wait for initialization of video to be complete
    sem_acquire_blocking(&video_initted);

    puts("Color bars ready, press SPACE to invert...");

    while (true) {
        // prevent tearing when we invert - if you're astute you'll notice this actually causes
        // a fixed tear a number of scanlines from the top. this is caused by pre-buffering of scanlines
        // and is too detailed a topic to fix here.
        scanvideo_wait_for_vblank();
        int c = getchar_timeout_us(0);
        switch (c) {
            case ' ':
                invert = !invert;
                printf("Inverted: %d\n", invert);
                break;
        }
    }
}

void draw_color_bar(scanvideo_scanline_buffer_t *buffer) {
    // figure out 1/32 of the color value
    uint line_num = scanvideo_scanline_number(buffer->scanline_id);
    int32_t color_step = 1 + (line_num * 7 / vga_mode.height);
    color_step = PICO_SCANVIDEO_PIXEL_FROM_RGB5(color_step & 1u, (color_step >> 1u) & 1u, (color_step >> 2u) & 1u);
    if (invert) color_step = -color_step;
    uint bar_width = vga_mode.width / 32;

    uint16_t *p = (uint16_t *) buffer->data;
    int32_t color = invert ? PICO_SCANVIDEO_PIXEL_FROM_RGB8(255, 255, 255) : 0;

    for (uint bar = 0; bar < 32; bar++) {
        *p++ = COMPOSABLE_COLOR_RUN;
        *p++ = color;
        *p++ = bar_width - 3;
        color += color_step;
    }

    // 32 * 3, so we should be word aligned
    assert(!(3u & (uintptr_t) p));

    // black pixel to end line
    *p++ = COMPOSABLE_RAW_1P;
    *p++ = 0;
    // end of line with alignment padding
    *p++ = COMPOSABLE_EOL_SKIP_ALIGN;
    *p++ = 0;

    buffer->data_used = ((uint32_t *) p) - buffer->data;
    assert(buffer->data_used < buffer->data_max);

    buffer->status = SCANLINE_OK;
}

void core1_func() {
    // initialize video and interrupts on core 1
    scanvideo_setup(&vga_mode);
    scanvideo_timing_enable(true);
    sem_release(&video_initted);

    while (true) {
        scanvideo_scanline_buffer_t *scanline_buffer = scanvideo_begin_scanline_generation(true);
        draw_color_bar(scanline_buffer);
        scanvideo_end_scanline_generation(scanline_buffer);
    }
}