/* M2make OS helpers (C).
 *
 * Dual-ABI file/time/process primitives for the M2make front-end.
 *
 * Two string ABIs exist and both are served here:
 *   - V3 (m2compiler-V3):  ARRAY OF CHAR is a descriptor (LONGCARD
 *     count + bytes (see runtime/syslib/shim.c).  V3 buffers handed
 *     to M2make are NUL-padded with count == capacity (verified by
 *     probe), so the _d variants scan for NUL bounded by the count.
 *   - GNU Modula-2: ARRAY OF CHAR is a NUL-terminated C buffer;
 *     the _s variants use it directly.
 *
 * Handle-only calls (close) are ABI-neutral and shared.
 * Only the string-taking calls need _d/_s pairs.
 * Readline never overruns: Modula-2 passes cap (HIGH(buf)+1) and at
 * most cap-1 bytes plus NUL are stored.  Physical lines longer than
 * the C temp (2048) continue on the next call; the Modula-2 scanner
 * keeps comment state across lines, so this only splits very long
 * lines (documented in the README).
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>

#define M2OS_TMP 2048

/* Copy a V3 descriptor to a NUL-terminated buffer (NUL scan bounded
   by the descriptor count, then by cap). */
static void desc2c(long *desc, char *buf, unsigned long cap)
{
    long count = desc[0];
    unsigned long bound;
    unsigned long i = 0;

    if (count < 0)
        count = 0;
    bound = (unsigned long)count;
    if (bound >= cap)
        bound = cap - 1;
    while (i < bound && ((char *)(desc + 1))[i] != 0) {
        buf[i] = ((char *)(desc + 1))[i];
        i++;
    }
    buf[i] = 0;
}

/* ---------------- existence ---------------- */

long m2osExistD(long *desc)
{
    char buf[4096];
    struct stat st;

    desc2c(desc, buf, sizeof buf);
    return (stat(buf, &st) == 0);
}

long m2osExistS(char *s)
{
    struct stat st;

    return (stat(s, &st) == 0);
}

/* ---------------- modification time ----------------
 * 1 with *t set on success, 0 when the file cannot be statted. */

long m2osMtimeD(long *desc, long long *t)
{
    char buf[4096];
    struct stat st;

    desc2c(desc, buf, sizeof buf);
    if (stat(buf, &st) != 0)
        return 0;
    *t = (long long)st.st_mtime;
    return 1;
}

long m2osMtimeS(char *s, long long *t)
{
    struct stat st;

    if (stat(s, &st) != 0)
        return 0;
    *t = (long long)st.st_mtime;
    return 1;
}

/* ---------------- process execution ----------------
 * Runs cmd via /bin/sh, returns the raw system() code. */

long m2osSystemD(long *desc)
{
    char buf[4096];

    desc2c(desc, buf, sizeof buf);
    return (long)system(buf);
}

long m2osSystemS(char *s)
{
    return (long)system(s);
}

/* ---------------- process exit (ABI-neutral) ---------------- */

void m2os_flush(void)
{
    fflush(NULL);
}

void m2osBye(long code)
{
    fflush(NULL);
    exit((int)code);
}

/* ---------------- command-line arguments (V3 side) ----------------
 * Skips argv[0] (the program name), unlike the raw SysShim.arg. */

static char *m2os_args[1024];
static long m2os_nargs = -1;

static void m2os_argv_init(void)
{
    static char cmd[65536];
    FILE *f;
    long i, n;

    if (m2os_nargs >= 0)
        return;
    m2os_nargs = 0;
    f = fopen("/proc/self/cmdline", "rb");
    if (f == NULL)
        return;
    n = (long)fread(cmd, 1, sizeof cmd - 1, f);
    fclose(f);
    if (n <= 0)
        return;
    cmd[n] = 0;
    i = 0;
    while (i < n && m2os_nargs < 1024) {
        while (i < n && cmd[i] == 0)
            i++;
        if (i >= n)
            break;
        m2os_args[m2os_nargs++] = &cmd[i];
        while (i < n && cmd[i] != 0)
            i++;
    }
}

long m2osArgcD(void)
{
    m2os_argv_init();
    if (m2os_nargs <= 0)
        return 0;
    return m2os_nargs - 1;
}

long m2osArgD(long i, long *desc, unsigned long cap)
{
    const char *a;
    unsigned long n, k;
    char *out;

    m2os_argv_init();
    if (cap == 0)
        return 0;
    if (i < 0 || i + 1 >= m2os_nargs)
        return 0;
    a = m2os_args[i + 1];
    n = (unsigned long)strlen(a);
    if (n >= cap)
        n = cap - 1;
    out = (char *)(desc + 1);
    for (k = 0; k < n; k++)
        out[k] = a[k];
    out[n] = 0;
    return 1;
}

/* ---------------- sequential text input ---------------- */

long m2osOpenreadD(long *desc)
{
    char buf[4096];

    desc2c(desc, buf, sizeof buf);
    return (long)fopen(buf, "r");
}

long m2osOpenreadS(char *s)
{
    return (long)fopen(s, "r");
}

/* Shared readline core: 1 with a line stored, 0 at end of file.
 * The trailing newline (and a preceding carriage return) is
 * stripped.  A final line without a newline still returns 1. */

static long readline_core(FILE *fp, char *out, unsigned long cap)
{
    static char tmp[M2OS_TMP];
    unsigned long n, i;

    if (cap == 0)
        return 0;
    if (fgets(tmp, sizeof tmp, fp) == NULL)
        return 0;
    n = (unsigned long)strlen(tmp);
    while (n > 0 && (tmp[n - 1] == 10 || tmp[n - 1] == 13))
        n--;
    if (n >= cap)
        n = cap - 1;
    for (i = 0; i < n; i++)
        out[i] = tmp[i];
    out[n] = 0;
    return 1;
}

long m2osReadlineD(long h, long *desc, unsigned long cap)
{
    char *out;

    if (h == 0 || cap == 0)
        return 0;
    out = (char *)(desc + 1);
    return readline_core((FILE *)h, out, cap);
}

long m2osReadlineS(long h, char *buf, unsigned long cap)
{
    if (h == 0)
        return 0;
    return readline_core((FILE *)h, buf, cap);
}

long m2osClose(long h)
{
    if (h != 0)
        fclose((FILE *)h);
    return 0;
}