/* WASI port of the microcore, for the bootstrap seed (seed/zc.wasm). reads the
   whole of stdin, runs the genome inside, writes stdout. needs no libc: the only
   imports are wasi_snapshot_preview1 fd_read, fd_write and proc_exit, so the same
   module runs under node (src/boot/run.mjs) and wasmtime. build with
   src/boot/mkseed.sh. */
#include "micro_port.h"

#define IMPORT(n) __attribute__((import_module("wasi_snapshot_preview1"), import_name(n)))
typedef struct { void *buf; unsigned long len; } Iov;
IMPORT("fd_read") int wasi_fd_read(int fd, Iov *iov, int n, unsigned long *got);
IMPORT("fd_write") int wasi_fd_write(int fd, Iov *iov, int n, unsigned long *put);
IMPORT("path_open") int wasi_path_open(int dir, int dirflags, const char *path, unsigned long len, int oflags, unsigned long long rights, unsigned long long inherit, int fdflags, int *fd);
IMPORT("fd_close") int wasi_fd_close(int fd);
IMPORT("proc_exit") _Noreturn void wasi_proc_exit(int code);

static unsigned char ibuf[65536], obuf[65536];
static int in_n, in_p, in_end, on;

static void fill(void)
{
	Iov v = { ibuf, sizeof ibuf }; unsigned long got = 0;
	in_p = 0; in_n = 0;
	if (in_end) return;
	if (wasi_fd_read(0, &v, 1, &got) || got == 0) { in_end = 1; return; }
	in_n = (int)got;
}
static void flush_fd(int fd, unsigned char *b, int n)
{
	while (n > 0) {
		Iov v = { b, (unsigned long)n }; unsigned long put = 0;
		if (wasi_fd_write(fd, &v, 1, &put) || put == 0) return;
		b += put; n -= (int)put;
	}
}

static unsigned char *mbase;
static UCell mcap;
Cell *micro_mem_alloc(UCell words)
{
	UCell need, pages;
	if (words > ((UCell)-1) / sizeof(Cell)) return 0;
	if (!mbase) mbase = (unsigned char *)((UCell)__builtin_wasm_memory_size(0) * 65536u);
	need = words * sizeof(Cell);
	if (need <= mcap) return (Cell *)mbase;
	pages = (need - mcap + 65535u) / 65536u;
	/* grow in large steps: some node releases crash in a gc that many small grows provoke; the module
	   starts with 128 MB, more than a compiler build needs, so a build never grows */
	if (pages < 1024) pages = 1024;
	if (__builtin_wasm_memory_grow(0, (int)pages) < 0) return 0;
	mcap += pages * 65536u;
	return (Cell *)mbase;
}

int micro_eof(void) { if (in_p >= in_n) fill(); return in_p >= in_n; }
int micro_getc(void) { return micro_eof() ? -1 : ibuf[in_p++]; }
void micro_putc(int c) { if (on == sizeof obuf) { flush_fd(1, obuf, on); on = 0; } obuf[on++] = (unsigned char)c; }
void micro_msg(const char *s) { int n = 0; while (s[n]) n++; flush_fd(2, (unsigned char *)s, n); }

Cell micro_syscall(Cell *mem, Cell op, Cell a, Cell b, Cell c)
{
	switch (op) {
	case 9:
		if (a == 0) return micro_mem_words();
		if (a == 1) return HEAP_LO;
		if (a == 2) return HEAP_HI;
		if (a == 3) return (Cell)micro_mem_words() * 8;
		return -1;
	case 1: {	/* open for reading, relative to the directory preopened as fd 3 (embed reads the library this way) */
		char path[1024]; int n = 0, fd = -1;
		if (b != 0) return -1;
		while (n < 1023 && a + n < (Cell)micro_mem_words() && mem[a + n]) { path[n] = (char)mem[a + n]; n++; }
		path[n] = 0;
		if (wasi_path_open(3, 1, path, (unsigned long)n, 0, 2 /* fd_read */, 0, 0, &fd)) return -1;
		return fd;
	}
	case 2: return a > 2 ? (wasi_fd_close((int)a) ? -1 : 0) : -1;
	case 3: {
		unsigned char t[512]; Cell n = 0; int i;
		if (c < 0 || b < 0 || b + c > (Cell)micro_mem_words()) return -1;
		while (n < c) {
			Iov v = { t, (unsigned long)(c - n > 512 ? 512 : c - n) }; unsigned long got = 0;
			if (a == 0) { while (n < c && !micro_eof()) mem[b + n++] = micro_getc(); break; }
			if (wasi_fd_read((int)a, &v, 1, &got) || got == 0) break;
			for (i = 0; i < (int)got; i++) mem[b + n + i] = t[i];
			n += (Cell)got;
		}
		return n;
	}
	case 4: {
		unsigned char t[512]; Cell n = 0; int i, k;
		if (c < 0 || b < 0 || b + c > (Cell)micro_mem_words() || (a != 1 && a != 2)) return -1;
		if (a == 1) { flush_fd(1, obuf, on); on = 0; }
		while (n < c) { k = c - n > 512 ? 512 : (int)(c - n); for (i = 0; i < k; i++) t[i] = (unsigned char)mem[b + n + i]; flush_fd((int)a, t, k); n += k; }
		return n;
	}
	case 21: return 1;
	case 23: return 0;
	}
	return -1;
}

void __multi3(unsigned long long *r, unsigned long long al, unsigned long long ah, unsigned long long bl, unsigned long long bh)
{
	unsigned long long a0 = al & 0xffffffffu, a1 = al >> 32, b0 = bl & 0xffffffffu, b1 = bl >> 32;
	unsigned long long p00 = a0 * b0, p01 = a0 * b1, p10 = a1 * b0, p11 = a1 * b1;
	unsigned long long mid = (p00 >> 32) + (p01 & 0xffffffffu) + (p10 & 0xffffffffu);
	r[0] = (p00 & 0xffffffffu) | (mid << 32);
	r[1] = p11 + (p01 >> 32) + (p10 >> 32) + (mid >> 32) + al * bh + ah * bl;
}

/* an input that starts with "ZCIMAGE\n" and a little-endian 64-bit byte count carries
   the image to boot ahead of the program: the bootstrap uses it to run each stage's
   compiler in this same module. any other input boots the embedded seed genome. */
int micro_port_image(Cell *mem, UCell org, UCell end)
{
	static const char tag[] = "ZCIMAGE\n";
	UCell n = 0, i, w; int k;
	if (micro_eof() || in_n - in_p < 16) return 0;
	for (k = 0; k < 8; k++) if (ibuf[in_p + k] != (unsigned char)tag[k]) return 0;
	in_p += 8;
	for (k = 0; k < 8; k++) n |= (UCell)micro_getc() << (8 * k);
	if (n % 8 || org + n / 8 > end) return -1;
	for (i = 0; i < n / 8; i++) {
		w = 0;
		for (k = 0; k < 8; k++) { int c = micro_getc(); if (c < 0) return -1; w |= (UCell)c << (8 * k); }
		mem[org + i] = (Cell)w;
	}
	return 1;
}

void _start(void)
{
	int r = micro_run();
	flush_fd(1, obuf, on); on = 0;
	if (r) wasi_proc_exit(r);
}