#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

const char *yes[] = {"SENTINEL_WILL_BE_REPLACED_BY_CMDLINE"}; // "CH32X03x", etc. element 0 is filled in by command-line
const char *no[]  = {"CH32V10x", "CH32V30x", "CH32V20x", "CH32X03x", "CH32V003"};

char       *WhitePull(const char **sti)
{
    const char *st  = *sti;
    int         len = 0;
    while ((*st == ' ' || *st == '\t' || *st == '(') && *st)
    {
        st++;
    }
    const char *sts = st;
    while (*st != ' ' && *st != '\t' && *st != '\n' && *st != ')' && *st != '(' && *st != 0)
    {
        st++;
        len++;
    }
    if (*st == ')') { st++; }
    char *ret = malloc(len + 1);
    memcpy(ret, sts, len);
    ret[len] = 0;
    *sti     = st;
    return ret;
}

int NYI(const char *s)
{
    int   ret = 2;
    char *wp  = WhitePull(&s);
    int   i;
    for (i = 0; i < sizeof(yes) / sizeof(yes[0]); i++)
        if (strcmp(yes[i], wp) == 0) ret = 1;
    if (ret != 1)
        for (i = 0; i < sizeof(no) / sizeof(no[0]); i++)
            if (strcmp(no[i], wp) == 0) ret = 0;
    free(wp);
    return ret;
}

int EvalSpec(const char *spl)
{
    int rsofar = 0;
    int i;
    int lastv = 0;
    int lasto = -1;
    int ret   = 0;
cont:
    char *wp  = WhitePull(&spl);
    int   def = -1;
    if (strcmp(wp, "defined") == 0) def = 1;
    if (strcmp(wp, "!defined") == 0) def = 2;
    if (def < 0) return 2;
    char *wpn = WhitePull(&spl);
    i         = NYI(wpn);
    // printf( "SPIN: %s/%s/%d/%d/%d\n", wp, wpn, i, def, lasto );
    if (i == 2) return 2;

    if (def == 2) i = !i;

    if (lasto == 1)
    {
        ret = lastv || i;
    }
    else if (lasto == 2)
        ret = lastv && i;
    else
        ret = i;

    char *wpa = WhitePull(&spl);
    // printf( "WPA: \"%s\"\n", wpa );
    lastv = ret;
    lasto = -1;
    // printf( "RET: %d\n", ret );
    if (strcmp(wpa, "||") == 0)
    {
        lasto = 1;
        goto cont;
    }
    else if (strcmp(wpa, "&&") == 0)
    {
        lasto = 2;
        goto cont;
    }
    else
        return ret;
}

// 0 for no
// 1 for yes
// 2 for indeterminate
int NoYesInd(const char *preprocc)
{
    int ret;
    int ofs = 0;
    if (strncmp(preprocc, "#if ", 4) == 0) ofs = 4;
    if (strncmp(preprocc, "#elif ", 6) == 0) ofs = 6;
    if (ofs)
    {
        ret = EvalSpec(preprocc + ofs);
        // printf( "SPEC: %d\n", ret );
    }
    else if (strncmp(preprocc, "#ifdef ", 7) == 0)
    {
        const char *ep = preprocc + 6;
        char       *wp = WhitePull(&ep);
        ret            = NYI(wp);
        free(wp);
    }
    else if (strncmp(preprocc, "#ifndef ", 8) == 0)
    {
        const char *ep = preprocc + 6;
        char       *wp = WhitePull(&ep);
        ret            = NYI(wp);
        if (ret < 2) ret = !ret;
        free(wp);
    }
    else
        ret = 2;
    // printf( "%d-> %s\n", ret, preprocc );
    return ret;
}

const char *sslineis(const char *line, const char *match)
{
    while (*line == ' ' || *line == '\t')
        line++;
    const char *linestart = line;
    while (*line && *match == *line)
    {
        line++;
        match++;
    }
    if (*match == 0)
        return linestart;
    else
        return 0;
}

int main(int argc, char **argv)
{
    if (argc != 3)
    {
        fprintf(stderr, "Syntax: transition [#define to trigger on] [file to convert]\nNo'd architectures:\n");
        int i;
        for (i = 0; i < sizeof(no) / sizeof(no[0]); i++)
        {
            fprintf(stderr, "\t%s\n", no[i]);
        }
        return -1;
    }

    yes[0]  = argv[1];

    FILE *f = fopen(argv[2], "r");
    if (!f)
    {
        fprintf(stderr, "Error: Could not open \"%s\"\n", argv[2]);
        return -2;
    }
    char  line[1024];
    char *l;

    int   depth = 0;

    // 0 = no
    // 1 = yes
    // 2 = indeterminate
    // 3 = super no. (I.e. after a true #if clause)
    int yesnoind[1024];
    yesnoind[0] = 1;

    while (l = fgets(line, sizeof(line) - 1, f))
    {
        const char *ss     = 0;
        int         nyi    = yesnoind[depth];
        int         waspre = 0;

        if ((ss = sslineis(line, "#if ")) || (ss = sslineis(line, "#ifdef ")) || (ss = sslineis(line, "#ifndef ")))
        {
            waspre = 1;
            // printf( "CHECK: %d/%s\n", depth, l );
            nyi = NoYesInd(ss);
            depth++;
            yesnoind[depth] = nyi;
        }
        else if ((ss = sslineis(line, "#elif ")))
        {
            if (nyi != 2)
            {
                waspre = 1;
                if (nyi == 1)
                {
                    nyi = 3;
                }
                else
                {
                    nyi = NoYesInd(ss);
                }
                // printf( "ELIF check: %s %d\n", ss, nyi );
                yesnoind[depth] = nyi;
            }
        }
        else if ((ss = sslineis(line, "#else")))
        {
            if (nyi != 2)
            {
                waspre = 1;
                if (yesnoind[depth] == 1)
                    nyi = 3;
                else
                    nyi = !yesnoind[depth];
                yesnoind[depth] = nyi;
            }
        }
        else if ((ss = sslineis(line, "#endif")))
        {
            waspre = 1;
            depth--;
            if (depth < 0)
            {
                fprintf(stderr, "UNTERMD IF\n");
            }
        }

        int thisv = nyi;
        int i;
        for (i = 0; i <= depth; i++)
        {
            // printf( "%d", yesnoind[i] );
            if (yesnoind[i] == 0 || yesnoind[i] == 3) thisv = 0;
        }
        // printf( ">>%s", l );

        if (thisv != 0 && thisv != 3 && (thisv != 1 || !waspre))
        {
            printf("%s", l);
        }
    }
}