/* flan_rt — the milestone-2 host ABI.
 *
 * This is the whole of it: argv, stdout, exit, and four text conversions
 * (plan.org, Milestone-2 primitives). Keeping the list this short is what
 * makes the wasm32 target cheap, because a primitive is the only thing
 * implemented twice.
 *
 * Every function here takes and returns scalars or an out-pointer. Nothing
 * returns a struct by value: the emitted .ll would then have to agree with the
 * platform's struct-return ABI, which is exactly the kind of thing that works
 * on x86-64 and silently does not on wasm32.
 */

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

/* [T] and string are both ptr+len — see Emit.ll. */
typedef struct { const uint8_t *ptr; int64_t len; } flan_slice;

static int    rt_argc;
static char **rt_argv;
static flan_slice *rt_args;   /* argv as [string], built once, never freed */

void flan_rt_init(int32_t argc, char **argv) {
  rt_argc = (int)argc;
  rt_argv = argv;
}

void flan_argv(flan_slice *out) {
  if (rt_args == NULL && rt_argc > 0) {
    rt_args = (flan_slice *)malloc(sizeof(flan_slice) * (size_t)rt_argc);
    for (int i = 0; i < rt_argc; i++) {
      rt_args[i].ptr = (const uint8_t *)rt_argv[i];
      rt_args[i].len = (int64_t)strlen(rt_argv[i]);
    }
  }
  out->ptr = (const uint8_t *)rt_args;
  out->len = (int64_t)rt_argc;
}

void flan_write_stdout(const uint8_t *p, int64_t n) {
  if (n > 0) fwrite(p, 1, (size_t)n, stdout);
}

void flan_exit(int32_t status) {
  fflush(stdout);
  exit((int)status);
}

/* The conversions are *text*: bytes->f64 parses "12.5", f64->bytes renders it.
 * calc-me's tokenizer needs the first, the prelude's printers the second. */

#define SCRATCH 64
static char scratch[SCRATCH];   /* rendered text lives here until the next call */

double flan_bytes_to_f64(const uint8_t *p, int64_t n) {
  char buf[512];
  size_t k = (size_t)n < sizeof buf - 1 ? (size_t)n : sizeof buf - 1;
  memcpy(buf, p, k);
  buf[k] = '\0';
  return strtod(buf, NULL);
}

int64_t flan_bytes_to_i64(const uint8_t *p, int64_t n) {
  char buf[64];
  size_t k = (size_t)n < sizeof buf - 1 ? (size_t)n : sizeof buf - 1;
  memcpy(buf, p, k);
  buf[k] = '\0';
  return (int64_t)strtoll(buf, NULL, 10);
}

/* %g so that 3.5 prints as "3.5" and not "3.500000" — calc-me's expected
 * output is a table of exact strings. */
void flan_f64_to_bytes(double x, flan_slice *out) {
  int n = snprintf(scratch, SCRATCH, "%g", x);
  out->ptr = (const uint8_t *)scratch;
  out->len = n < 0 ? 0 : (int64_t)n;
}

void flan_i64_to_bytes(int64_t x, flan_slice *out) {
  int n = snprintf(scratch, SCRATCH, "%lld", (long long)x);
  out->ptr = (const uint8_t *)scratch;
  out->len = n < 0 ? 0 : (int64_t)n;
}

/* Bounds failures. The emitted code branches here and then falls off the end
 * with `unreachable`, so these must not return — the same explicit shape as
 * every other non-local exit, which is what keeps wasm32 free of unwinding.
 *
 * The location is passed as ptr+len because that is what a Flan string already
 * is; nothing here allocates. Exit 134 is abort()'s status without abort()'s
 * signal, so the same assertion should hold once wasm32 builds.
 *
 * stdout is flushed *before* the message: stderr is unbuffered and a
 * redirected stdout is not, so without this the error appears above the output
 * that led to it. */

static _Noreturn void rt_die(void) {
  fflush(stdout);
  fflush(stderr);
  exit(134);
}

_Noreturn void flan_bounds_fail(const uint8_t *loc, int64_t loclen,
                                int64_t idx, int64_t len) {
  fflush(stdout);
  fprintf(stderr, "%.*s: index %lld is out of bounds for length %lld\n",
          (int)loclen, (const char *)loc, (long long)idx, (long long)len);
  rt_die();
}

_Noreturn void flan_slice_fail(const uint8_t *loc, int64_t loclen,
                               int64_t lo, int64_t hi, int64_t len) {
  fflush(stdout);
  fprintf(stderr, "%.*s: slice [%lld %lld) is out of bounds for length %lld\n",
          (int)loclen, (const char *)loc, (long long)lo, (long long)hi,
          (long long)len);
  rt_die();
}