#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdio.h>
#include <math.h>

#include "val.h"
#include "vm.h"
#include "mem.h"
#include "dis.h"


Chunk chunk_new(State *S) {
	return (Chunk){ 0 };
}

size_t chunk_wbc(State *S, Chunk *ch, uint8_t byte) {
	if (ch->bc.len == ch->bc.cap) {
		size_t newsz = (ch->bc.cap == 0 ? 8 : ch->bc.cap * 2);
		ch->bc.d = RENEW_ARR(S, ch->bc.d, uint8_t, ch->bc.cap, newsz);
		ch->bc.cap = newsz;
	}
	size_t ix = ch->bc.len;
	ch->bc.d[ix] = byte;
	ch->bc.len ++;
	return ix;
}
size_t chunk_wconst(State *S, Chunk *ch, Val v) {
	for (int i = 0; i < ch->consts.len; i ++)
		if (val_equal(v, ch->consts.d[i])) return i;

	if (ch->consts.len == ch->consts.cap) {
		size_t newsz = (ch->consts.cap == 0 ? 8 : ch->consts.cap *2);
		ch->consts.d = RENEW_ARR(S, ch->consts.d, Val, ch->consts.cap, newsz);
		ch->consts.cap = newsz;
	}

	size_t ix = ch->consts.len;
	ch->consts.d[ix] = v;
	ch->consts.len ++;
	return ix;
}

Thread thread_new(State *S) {
	Thread th = (Thread){ 0 };
	for (int i = 0; i < STACKSIZE; i++) {
		th.stack[i] = VAL_NIL;
	}
	return th;
}


int runvm(State *S) {
	Thread *th = S->th;
	Chunk *ch = th->ch;

	int status = 1;

	if (S->do_disasm) {
		disasm_chunk(ch);
		puts("---");
	}

#define RBYTE() (ch->bc.d[th->ip++])
#define RSHORT() (th->ip += 2, (uint16_t)( ch->bc.d[th->ip-2] | ch->bc.d[th->ip-1] << 8 ))

#define PUSH(v) th->stack[th->sp++] = v;
#define POP()   (th->stack[--th->sp])
#define PEEK()  (th->stack[th->sp-1])

	while (1) {
		uint8_t instr = RBYTE();
		switch (instr) {
		case OP_RET:
			status  = 0;
			goto done;
			break;
		case OP_LOADK: {
			uint8_t cix = RBYTE();
			Val v = ch->consts.d[cix];
			PUSH(v);
			// printf("   (pushing ");
			// print_val(v);
			// printf(")\n");
			break;
		}
		case OP_PUTS:
			println_val(PEEK());
			break;
		case OP_PRINT:
			print_val(PEEK());
			break;
		case OP_DROP:
			--th->sp;
			break;

		case OP_SKIP: {
			uint16_t offset = RSHORT();
			th->ip += offset;
			break;
		}
		case OP_REDO: {
			uint16_t offset = RSHORT();
			th->ip -= offset;
			break;
		}
		case OP_0BRANCH: {
			uint16_t offset = RSHORT();
			bool cond = is_truthy(POP());
			if (!cond)
				th->ip += offset;
			break;
		}

		case OP_GETGLOBAL: {
			uint8_t cix = RBYTE();
			Val varname = ch->consts.d[cix];
			if (!IS_STRING(varname)) {
				printf("global names must be string, not %s\n",
					typename_str(varname));
				goto done;
			}
			Val v = ht_get(S, &S->globals, AS_STRING(varname));
			PUSH(v);
			break;
		}
		case OP_SETGLOBAL: {
			uint8_t cix = RBYTE();
			Val varname = ch->consts.d[cix];
			if (!IS_STRING(varname)) {
				printf("global names must be string, not %s\n",
					typename_str(varname));
				goto done;
			}
			Val v = PEEK();

			ht_put(S, &S->globals, AS_STRING(varname), v);
			break;
		}

#define BINARY_OP(opcode, OP, RET_TYPE) \
		case opcode: { \
			Val b = POP(); \
			Val a = POP(); \
			if (!IS_NUM(a) || !IS_NUM(b)) { \
				printf("can't do arithmetic on %s and %s\n", \
					typename_str(a), typename_str(b)); \
				goto done; \
			} \
			PUSH(RET_TYPE(AS_NUM(a) OP AS_NUM(b))); \
			} \
			break;
#define ARITH_OP(opcode, OP) BINARY_OP(opcode, OP, VAL_NUM)
#define BOOL_OP(opcode, OP)  BINARY_OP(opcode, OP, VAL_BOOL)
			ARITH_OP(OP_ADD, +)
			ARITH_OP(OP_SUB, -)
			ARITH_OP(OP_MUL, *)
			ARITH_OP(OP_DIV, /)
			BOOL_OP(OP_CMP, <)
#undef BINARY_OP
#undef ARITH_OP
#undef BOOL_OP
		case OP_EQU: {
			Val b = POP();
			Val a = POP();
			PUSH(VAL_BOOL(val_equal(a,b)));
			break;
		}
		case OP_MOD: {
			Val b = POP();
			Val a = POP();
			if (!IS_NUM(a) || !IS_NUM(b)) {
				printf("can't do arithmetic on %s and %s", 
					typename_str(a), typename_str(b));
				goto done;
			}
			PUSH(VAL_NUM(fmod(AS_NUM(a), AS_NUM(b))));
			} 
			break;


		case OP_NIL: PUSH(VAL_NIL); break;
		case OP_TRUE: PUSH(VAL_TRUE); break;
		case OP_FALSE: PUSH(VAL_FALSE); break;

		}
	}
	done:;
	return status;
}

#undef RBYTE
#undef RSHORT
#undef PUSH
#undef POP
#undef PEEK