#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#pragma clang diagnostic ignored "-Wreturn-type"
#pragma clang diagnostic ignored "-Wc23-extensions"

// clang-format off
#define S 65536
#define H !--c?
#define J while
m[S],c,a;pu(){J((c=m[m[7]++]))H*m=m[m[7]++]:c--<9?!a?m[c]=*m:0:8>(c-=8)?*m=m[c]:!(c-=8)?m[m[1]]=*m:H*m=a:H a+=*m:H a-=*m:H a=!a:H a=0:0;}
// clang-format on

// a is acc
// first 8 memory bytes are registers actually
// c is pc, read from m[7]

// --- opcodes ---
// 0 = halt DONE
// 1 = const in r0 DONE
// 2...9 = r0 in rX (only if acc is zero) DONE
// 10...17 = rX in r0 DONE
// 18 = r0 in m[r1] DONE
// 19 = acc in r0 DONE
// 20 = acc += r0 DONE
// 21 = acc -= r0 DONE
// 22 = acc = !acc DONE
// 23 = acc = 0 DONE
// for ops 2..9 and 10..17 it basically works like this: 2 handles r0, 3 r1, 4 r2, etc. 10 handles
// r0, 11 r1, 12 r2 and so on.

// compiler!
// the switch skips whitespace. then, the beautiful loop thingymajigy emits bytecode.

// clang-format off
#define W case
#define Q goto M;
char R[]={
#embed"t"
};K;char*as(char*I,int*O){char*V=R;J((K=*I)){V=R;switch(K){W 32:W 10:W 9:I++;Q;W 35:J(*++I!=10);Q}strncmp("con ",I,4)?:({*O++=1,*O++=atoi(I+=4);J(*I>47&*I<58)I++;Q});J(*V)V+=3,(strncmp(V-3,I,3)?:({*O++=*V;I+=3;Q})),V+=2;return I;M:}return 0;}
// clang-format on

#undef Q
#undef H
#undef W
#undef S
#undef J

#ifndef __WRAPPER

// runs pu until exit code != 2,
// that exit code is an interrupt for talking to the emulated hardware
int emu() {
    while (1) {
        pu();
        int e_code = m[ 0 ];

        if (e_code != 2) return e_code;

        // handle hardware interrupts
        int int_code = m[ 1 ];

        // 0: output string
        if (int_code == 0) {
            int ptr  = m[ 2 ];
            int size = m[ 3 ], i = 0;

            for (; i < size; i++) putchar(m[ ptr++ ]);
            write(STDOUT_FILENO, &m[ ptr ], size);
        }

        // 1: input character
        else if (int_code == 1) {
            m[ 2 ] = getchar();
        }

        else {
            // unknown interrupt. what to do?
        }

        m[ 0 ] = 0;
        m[ 7 ]++;
    }
}

char R_backup[] = "hlt\0 ar1\2 ar2\3 ar3\4 ar4\5 ar5\6 ar6\7 ar7\x8 ar8\x9 r1a\xA r2a\xB r3a\xC "
                  "r4a\xD r5a\xE r6a\xF r7a\20 r8a\21 mem\22 aca\23 add\24 sub\25 not\26 clr\27";

int main(int argc, char **argv) {
    if (access("t", F_OK)) {
        // patch the instruction table incase you removed it.
        printf("you've deleted t! i'll write it again for you.\n\n");
        FILE *fp = fopen("t", "w+");
        fwrite(R_backup, 1, sizeof(R_backup), fp);
        fclose(fp);
        memcpy(R, R_backup, sizeof(R_backup));
    }

    if (argc == 1) {
        printf("Usage:\n    %s <filename>", argv[ 0 ]);
        exit(1);
    }

    // read code
    FILE *fp = fopen(argv[ 1 ], "r");
    fseek(fp, 0, SEEK_END);
    int sz = ftell(fp);
    rewind(fp);
    char code[ sz + 1 ];
    fread(code, 1, sz, fp);
    code[ sz ] = 0;
    fclose(fp);

    // set pc
    m[ 7 ] = 1024;
    // assemble
    char *fail_point = as(code, &m[ 1024 ]);

    if (fail_point != 0) {
        int error_pos = (int) (fail_point - code);
        int i;

        int line = 1, col = 1;
        for (i = 0; i < error_pos && i < sz; i++) {
            if (code[ i ] == '\n') {
                line++;
                col = 1;
            } else {
                col++;
            }
        }

        fprintf(
            stderr, "Assembly failed at line %d, column %d (position %d):\n", line, col, error_pos);

        int line_start = error_pos;
        while (line_start > 0 && code[ line_start - 1 ] != '\n') { line_start--; }

        int line_end = error_pos;
        while (line_end < sz && code[ line_end ] != '\n' && code[ line_end ] != '\0') {
            line_end++;
        }

        fprintf(stderr, "  ");
        for (i = line_start; i < line_end; i++) { fputc(code[ i ], stderr); }
        fprintf(stderr, "\n");

        fprintf(stderr, "  ");
        for (i = line_start; i < error_pos; i++) { fputc(' ', stderr); }
        fprintf(stderr, "^ parsing stopped here\n");

        exit(1);
    }

    // run emulation
    emu();
}
#endif