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

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



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;

	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])
// 1 is TOS
#define PEEKN(n) (th->stack[th->sp-n])

	while (1) {
		ch = th->ch;
		if (S->do_trace) {
			printf("\t[%lu -> %lu] : ",th->fp, th->sp);
			for (int i = th->fp; i < th->sp; i++) {
				printf("(%d) ",i);
				print_val(th->stack[i]);
				printf(" ; ");
			}
			printf("\n%p ",(void *)ch);
			disasm_instr(ch, th->ip);
		}
		uint8_t instr = RBYTE();
		switch (instr) {
		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_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];
			CHECK(IS_STRING(varname), "global names must be string");
			Val v = ht_get(S, &S->globals, AS_STRING(varname));
			PUSH(v);
			if (IS_NIL(v)) {
				printf("warning: nil global read %s\n", AS_CSTRING(varname));
			}
			break;
		}
		case OP_SETGLOBAL: {
			uint8_t cix = RBYTE();
			Val varname = ch->consts.d[cix];
			CHECK(IS_STRING(varname), "global names must be string");
			Val v = PEEK();

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

		case OP_GETLOCAL: {
			uint8_t lidx = RBYTE();
			PUSH(th->stack[th->fp + lidx]);
			break;
		}
		case OP_SETLOCAL: {
			uint8_t lidx = RBYTE();
			Val v = PEEK();
			th->stack[th->fp + lidx] = v;
			break;
		}

#define BINARY_OP(opcode, OP, RET_TYPE) \
		case opcode: { \
			Val b = POP(); \
			Val a = POP(); \
		    CHECK(IS_NUM(a) && IS_NUM(b), "can only do arithmetic on num"); \
			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();
			CHECK(IS_NUM(a) && IS_NUM(b), "can only do arithmetic on num");
			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;

		case OP_TAILCALL:
		case OP_CALL: {
			// nargs + 1 = function and args
			uint8_t len = RBYTE();
			uint8_t nargs = len - 1;
			Val callee = PEEKN(len);

			if (IS_FUNC(callee)) {
				ObjFunc *func = AS_FUNC(callee);
				CHECK(nargs == func->arity, "func needs exactly %d args, but got %d",func->arity,nargs);

				CHECK(th->rsp < MAXDEPTH, "rstack overflow");
				if (instr != OP_TAILCALL) {
					StackFrame *sf = &th->rstack[th->rsp++];
					sf->ip = th->ip;
					sf->ch = th->ch;
					sf->fp = th->fp;

					th->ip = 0;
					th->ch = &func->ch;
					th->fp = th->sp - len;
				} else {
					// xxx might invalidate open upvalues
					memmove(&th->stack[th->fp], &th->stack[th->sp - len], len*sizeof(Val));
					th->sp = th->fp + len;
					th->ip = 0;
					th->ch = &func->ch;

					StackFrame *cur_sf = &th->rstack[th->rsp];
					cur_sf->ip = th->ip;
					cur_sf->ch = th->ch;
					cur_sf->fp = th->fp;
				}
			} else if (IS_CFUNC(callee)) {
				Val *firstarg = &th->stack[th->sp - nargs];
				Val res = AS_CFUNC(callee)(S, nargs, firstarg);
				th->sp -= len;
				PUSH(res);
			} else if (IS_ARR(callee)) {
				ObjArr *arr = AS_ARR(callee);
				CHECK(len == 2, "can only index arr with single argument");
				Val vix = PEEK();
				CHECK(IS_NUM(vix), "can only index numerically");
				size_t ix = (size_t)AS_NUM(vix);
				Val res = objarr_get(S, arr, ix);
				th->sp -= 2;
				PUSH(res);
			} else {
				ERROR("cannot call %s",typename_str(callee));
			}
			break;
		}

		case OP_SETIDX: {
			Val vix = POP();
			Val varr = POP();
			Val v = PEEK();
			CHECK(IS_NUM(vix), "can only index numerically");
			CHECK(IS_ARR(varr), "can only set index on array");
			size_t ix = (size_t)AS_NUM(vix);
			ObjArr *arr = AS_ARR(varr);
			objarr_put(S, arr, ix, v);
			break;
		}
	
		case OP_ENDSCOPE: {
			uint8_t nlocals = RBYTE();
			Val retval = POP();
			th->sp -= nlocals;
			PUSH(retval);
			break;
		}

		case OP_RET: {
			StackFrame *sf = &th->rstack[--th->rsp]; 

			th->ip = sf->ip;
			th->ch = sf->ch;
			th->fp = sf->fp;
			break;
		}
		case OP_HALT:
			return 0;

		case OP_ARRNEW: {
			ObjArr *a = objarr_new(S);
			PUSH(VAL_OBJ(a));
			break;
		}
		case OP_ARRAPPEND: { 
			Val v = POP();
			Val a = PEEK();
			CHECK(IS_ARR(a), "can only append to array");
			ObjArr *arr = AS_ARR(a);
			objarr_append(S, arr, v);
			break;
		}
		case OP_ARRLEN: {
			Val v = POP();
			CHECK(IS_ARR(v), "can only get length of array");
			ObjArr *arr = AS_ARR(v);
			PUSH(VAL_NUM(arr->len));
			break;
		}
		default:
			ERROR("unknown opcode");

		}


	}
}

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