/* WebAssembly port of the microcore. the page hands the program over as
   bytes, calls run(), and gets output back one byte at a time through the
   one import. build with src/web/build.sh; nothing here needs libc. */
#include "micro_port.h"

extern void js_putc(int c);
extern void js_msg(int c);

static unsigned char inbuf[1 << 20];
static int inn, inp;

/* where the page writes the program, and how it says how long it is */
unsigned char *wasm_input(void) { return inbuf; }
int wasm_input_cap(void) { return (int)sizeof inbuf; }
void wasm_set_input(int n) { inn = n; inp = 0; }

/* the machine's memory: the linear memory above everything the module has in it.
   the base is fixed when the first machine is made, and a grow only adds pages on
   the top, so the base never moves. */
static unsigned char *mbase;
static UCell mcap;	/* bytes of machine memory the module has grown for */

Cell *micro_mem_alloc(UCell words)
{
	UCell need, extra, pages;
	if (words > ((UCell)-1) / sizeof(Cell)) return 0;
	if (!mbase) {
		mbase = (unsigned char *)((UCell)__builtin_wasm_memory_size(0) * 65536u);
		mcap = 0;
	}
	need = words * sizeof(Cell);
	if (need <= mcap) return (Cell *)mbase;
	extra = need - mcap;
	pages = (extra + 65535u) / 65536u;
	if (__builtin_wasm_memory_grow(0, (int)pages) < 0) return 0;
	mcap += pages * 65536u;	/* wasm zeroes the pages it grows by */
	return (Cell *)mbase;
}

int micro_getc(void) { return inp < inn ? inbuf[inp++] : -1; }
int micro_eof(void) { return inp >= inn; }
void micro_putc(int c) { js_putc(c & 255); }
void micro_msg(const char *s) { while (*s) js_msg(*s++); }

Cell micro_syscall(Cell *mem, Cell op, Cell a, Cell b, Cell c)
{
	switch (op) {
	case 9:		/* memory: the size of the machine and its heap */
		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 7:		/* exit: the page sees run() return */
		return -1;
	case 21:	/* argc: the page has no command line, so <eval> alone */
		return 1;
	case 22:	/* argv: entry 0 is <eval>, as in zy(1) */
		if (a != 0) return -1;
		if (!b) return 6;
		if (c < 7 || b + 6 >= micro_mem_words()) return -1;
		{
			static const char lead[] = "<eval>";
			int i;
			for (i = 0; i < 6; i++) mem[b + i] = (unsigned char)lead[i];
			mem[b + 6] = 0;
		}
		return 6;
	case 23:	/* envc: a page has no environment */
		return 0;
	}
	return -1;
}

/* the core multiplies 64 by 64 into 128 bits for the float helpers; wasm has no
   such instruction and there is no compiler runtime to link, so this is it */
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;
}

int wasm_run(void) { return micro_run(); }