#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <assert.h>

#include "dcpu16.h"
#include "display.h"
#include "chargen-4x8.h"

/* preliminary attempt at handling display */
/* currently keeps display state in buffer, and just updates a PNM file on each screen update */

#define DISPLAY_BASE 0x8000
#define DISPLAY_END  0x8179
#define DISPLAY_CELL_MAP 0x8180
#define DISPLAY_MISC 0x8280

#define CELL_X 32
#define CELL_Y 12

#define CELL_X_SZ 4
#define CELL_Y_SZ 8

#define PIX_X 160
#define PIX_Y 128
#define PIX_BORDER 16

/* total display is 160 pixels by 128 pixels */
/* active display is 32x12 cells (each 4x8 pixels), surrounded by 16 pixel border */
/* cells are rendered from cell map, which is bitmap of two words, defining four eight-bit columns */

struct pixel_ {
    char r;
    char g;
    char b;
};

static inline
DPIX pcolor_(unsigned int c) {
    DPIX p = { 0, 0, 0 };

    switch (c) {
        case 0x1: p.r=0x00, p.g=0x00, p.b=0xaa; break;  /* dark blue */
        case 0x2: p.r=0x00, p.g=0xaa, p.b=0x00; break;  /* green */
        case 0x3: p.r=0x00, p.g=0xaa, p.b=0xaa; break;  /* cyan */
        case 0x4: p.r=0xaa, p.g=0x00, p.b=0x00; break;  /* red */
        case 0x5: p.r=0xaa, p.g=0x00, p.b=0xaa; break;  /* magenta */
        case 0x6: p.r=0xaa, p.g=0xaa, p.b=0x55; break;  /* yellow [] */
        case 0x7: p.r=0xaa, p.g=0xaa, p.b=0xff; break;  /* pale blue */
        case 0x8: p.r=0x55, p.g=0x55, p.b=0x55; break;  /* grey */
        case 0x9: p.r=0x55, p.g=0x55, p.b=0xff; break;  /* also blue */
        case 0xa: p.r=0x55, p.g=0xff, p.b=0x55; break;  /* light green */
        case 0xb: p.r=0x55, p.g=0xff, p.b=0xff; break;  /* light cyan */
        case 0xc: p.r=0xff, p.g=0x55, p.b=0x55; break;  /* light red */
        case 0xd: p.r=0xff, p.g=0x55, p.b=0xff; break;  /* light magenta */
        case 0xe: p.r=0xff, p.g=0xff, p.b=0x55; break;  /* light yellow */
        case 0xf: p.r=0xff, p.g=0xff, p.b=0xff; break;  /* white */
        default:  p.r=0x00, p.g=0x00, p.b=0x00;         /* black */
    }

    return p;
}

/* should this just flood-fill entire display? */
static inline
void display_draw_border(DPIX *pixbuf, DPIX color) {
    size_t x, y;
    size_t i;

    /* top */
    for (y = 0; y < PIX_BORDER; y++) {
        for (x = 0; x < PIX_X; x++) {
            i = (y * PIX_X) + x;
            pixbuf[i] = color;
            i = ((PIX_Y - y) * PIX_X) + x;
            pixbuf[i] = color;
        }
    }

    /* sides */
    for (y = PIX_BORDER; y < (PIX_Y - PIX_BORDER + 1); y++)
        for (x = 0; x < PIX_BORDER; x++) {
            i = (y * PIX_X) + x;
            pixbuf[i] = color;
            pixbuf[i + (PIX_X - PIX_BORDER)] = color;
        }

}

/* render a character cell to the display */
static inline
void display_draw_cell(DPIX *pixbuf, DCPU16_WORD *cell_map, DCPU16_WORD index, int cell_x, int cell_y, DPIX fg, DPIX bg) {
    DPIX *cellstart = pixbuf; /* start of display */
    unsigned int pix_x, pix_y;
    unsigned char *cell_bitmap = (unsigned char *)(cell_map + (index * sizeof index));

    assert(cell_x < CELL_X);
    assert(cell_y < CELL_Y);

    cellstart += (PIX_X * PIX_BORDER); /* skip top border */

    cellstart += (CELL_Y_SZ * PIX_X) * cell_y; /* skip down to row */

    cellstart += PIX_BORDER; /* skip side border */

    cellstart += (CELL_X_SZ) * cell_x; /* skip to column */

    for (pix_x = 0; pix_x < CELL_X_SZ; pix_x++) {
        for (pix_y = 0; pix_y < CELL_Y_SZ; pix_y++) {
            if ((cell_bitmap[pix_x] >> pix_y) & 0x01)
                cellstart[((CELL_Y_SZ - pix_y - 1) * PIX_X) + pix_x] = fg;
            else
                cellstart[((CELL_Y_SZ - pix_y - 1) * PIX_X) + pix_x] = bg;
        }
    }
}

/* write pnm file */
void display_pnm_write(DPIX *pixbuf, const char *filename) {
    size_t i;
    FILE *f;

    f = fopen(filename, "w");
    if (f == NULL) {
        fprintf(stderr, "%s('%s'):%s\n", "fopen", filename, strerror(errno));
        return;
    }

    /* write header... */
    /* PNM binary */
    /* x y */
    /* max value */
    fprintf(f, "P6\n%d %d\n255\n", PIX_X, PIX_Y);

    /* write out image bytes in r g b order */
    for (i = 0; i < PIX_X * PIX_Y; i++) {
        fwrite(&pixbuf[i].r, 1, 1, f);
        fwrite(&pixbuf[i].g, 1, 1, f);
        fwrite(&pixbuf[i].b, 1, 1, f);
    }

    fclose(f);
}


/* the callback to register to be run on display init/reset */
/* currently this populates the chargen map 'from rom'.. */
/* and clears the display buffers */
void display_reset_fn(struct dcpu16 *vm, dcpu16_acct_event e, DCPU16_WORD addr, void *data) {
    DPIX *pixbuf = (DPIX *)data;

    (void)e, (void)addr;

    fprintf(stderr, "DEBUG: event:%u\n", e);

    fprintf(stderr, "DEBUG: loading chargen map from 0x%04x to 0x%04x (%zuo)\n",
            DISPLAY_CELL_MAP,
            DISPLAY_CELL_MAP + (unsigned short)(sizeof chargen_4x8_glyphs / sizeof addr),
            sizeof chargen_4x8_glyphs);
    memcpy(vm->ram + DISPLAY_CELL_MAP, chargen_4x8_glyphs, sizeof chargen_4x8_glyphs);

    fprintf(stderr, "DEBUG: clearing display buffer from 0x%04x to 0x%04x (%zuo)\n",
            DISPLAY_BASE,
            DISPLAY_END,
            (DISPLAY_END - DISPLAY_BASE) * sizeof *(vm->ram));
    memset(vm->ram + DISPLAY_BASE, 0, (DISPLAY_END - DISPLAY_BASE) * sizeof *(vm->ram));

    fprintf(stderr, "DEBUG: clearing pixel buffer (%zuo)\n",
            PIX_X * PIX_Y * sizeof *pixbuf);
    memset(pixbuf, 0, PIX_X * PIX_Y * sizeof *pixbuf);
}

/* the callback to register with the cpu for watching memory updates */
/* user data is an allocated display buffer */
void display_fn(struct dcpu16 *vm, dcpu16_acct_event e, DCPU16_WORD addr, void *data) {
    const char * const outfile = "dcpu16-display.pnm";
    DPIX *pixbuf = (DPIX *)data;
    unsigned char index, blink, bg, fg;
    unsigned int cell_x, cell_y;

    (void)e;

    if (addr < DISPLAY_BASE || addr > DISPLAY_MISC)
        return;

    if (addr > DISPLAY_END && addr < DISPLAY_MISC) {
        unsigned char updated_index = addr - DISPLAY_CELL_MAP;
        /* a cell map was updated, refresh entire screen */
        for (cell_x = 0; cell_x < CELL_X; cell_x++) {
            for (cell_y = 0; cell_y < CELL_Y; cell_y++) {
                addr = DISPLAY_BASE + cell_x + (cell_y * CELL_X);
                index = vm->ram[addr] & 0x7f;
                if (index != updated_index)
                    continue;
                blink = (vm->ram[addr] >> 7) & 0x01;
                bg = (vm->ram[addr] >> 8) & 0x0f;
                fg = (vm->ram[addr] >> 12) & 0x0f;
                display_draw_cell(pixbuf, vm->ram + DISPLAY_CELL_MAP, index, cell_x, cell_y, pcolor_(fg), pcolor_(bg));
            }
        }

        display_pnm_write(pixbuf, outfile);
        return;
    }

    if (addr == DISPLAY_MISC) {
        /* new border color */
        char border = vm->ram[addr] & 0x0f;
        fprintf(stderr, "display event: new border\n");
        display_draw_border(pixbuf, pcolor_(border));

        display_pnm_write(pixbuf, outfile);
        return;
    }

    cell_x = (addr - DISPLAY_BASE) % CELL_X;
    cell_y = (addr - DISPLAY_BASE) / CELL_X;

    index = vm->ram[addr] & 0x7f;
    blink = (vm->ram[addr] >> 7) & 0x01;
    bg = (vm->ram[addr] >> 8) & 0x0f;
    fg = (vm->ram[addr] >> 12) & 0x0f;

    fprintf(stderr, "display event: cell %ux%u:%u '%c'\n", cell_x, cell_y, index, index);

    display_draw_cell(pixbuf, vm->ram + DISPLAY_CELL_MAP, index, cell_x, cell_y, pcolor_(fg), pcolor_(bg));
    display_pnm_write(pixbuf, outfile);
}

/* init the pixel buffer */
DPIX *display_init_pixbuf(void) {
    DPIX *pixbuf;

    pixbuf = calloc(PIX_X * PIX_Y, sizeof *pixbuf);

    return pixbuf;
}