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

#include "vm.h"
#include "ast.h"
#include "read.h"
#include "state.h"

static size_t placeholder(State *S, Chunk *ch) {
	size_t old_ix = ch->bc.len;
	chunk_wbc(S, ch, 0x00);
	chunk_wbc(S, ch, 0x00);
	return old_ix;
}

static void patch(State *S, Chunk *ch, size_t addr, uint16_t val) {
	ch->bc.d[addr] = val & 0xff;
	ch->bc.d[addr+1] = (val & 0xff00) >> 8;
}


static void compile_node(State *S, Chunk *ch, AstNode a) {
	switch (a.ty) {
	case AST_IDENT:;
		char *ident = a.as.str;

		if (0 == strcmp(ident, "true")) chunk_wbc(S, ch, OP_TRUE);
		else if (0 == strcmp(ident, "false")) chunk_wbc(S, ch, OP_FALSE);
		else if (0 == strcmp(ident, "nil")) chunk_wbc(S, ch, OP_NIL);
		else {
			// global read
			ObjString *o = objstring_copy_cstr(S, a.as.str);
			chunk_wbc(S, ch, OP_GETGLOBAL);
			chunk_wbc(S, ch, chunk_wconst(S, ch, VAL_OBJ(o)));
		}
		break;
	case AST_NUM:
		chunk_wbc(S, ch, OP_LOADK);
		chunk_wbc(S, ch, chunk_wconst(S, ch, VAL_NUM(a.as.num)));
		break;
	case AST_STRING: {
		ObjString *o = objstring_copy_cstr(S, a.as.str);
		chunk_wbc(S, ch, OP_LOADK);
		chunk_wbc(S, ch, chunk_wconst(S, ch, VAL_OBJ(o)));
		break;
	}
	case AST_LIST: {
		AstVec l = a.as.list;
		#define CK(cond, msg) if (!(cond)) { puts(msg); exit(1); }
		CK(l.len > 0, "can't handle empty list");
		CK(l.vals[0].ty == AST_IDENT, "can only call ops");

		char *name = l.vals[0].as.str;

		if (0 == strcmp(name, "print")) {
			CK(l.len == 2, "print requires exactly 1 argument");
			compile_node(S, ch, l.vals[1]);
			chunk_wbc(S, ch, OP_PRINT);
		} else if (0 == strcmp(name, "set")) {
			CK(l.len == 3, "set requires exactly 2 arguments");
			AstNode ident = l.vals[1];
			CK(ident.ty == AST_IDENT, "set's first argument must be identifier");

			ObjString *o = objstring_copy_cstr(S, ident.as.str);
			compile_node(S, ch, l.vals[2]);
			chunk_wbc(S, ch, OP_SETGLOBAL);
			chunk_wbc(S, ch, chunk_wconst(S, ch, VAL_OBJ(o)));
		} else if (0 == strcmp(name, "do")) {
			for (int i = 1; i < l.len - 1; i++) {
				compile_node(S, ch, l.vals[i]);
				chunk_wbc(S, ch, OP_DROP);
			}
			compile_node(S, ch, l.vals[l.len - 1]);
		} else if (0 == strcmp(name, "if")) {
			CK(l.len == 4, "if requires exactly 3 arguments");
			// (if cond if-true if-false)
			// cond
			// 0branch ->A
			// if-true
			// skip ->B
			// A: if-false
			// B:
			compile_node(S, ch, l.vals[1]);
			chunk_wbc(S, ch, OP_0BRANCH);
			size_t ph_a = placeholder(S, ch);
			compile_node(S, ch, l.vals[2]);
			chunk_wbc(S, ch, OP_SKIP);
			size_t ph_b = placeholder(S, ch);
			size_t dest_a = ch->bc.len;
			compile_node(S, ch, l.vals[3]);
			size_t dest_b = ch->bc.len;

			patch(S, ch, ph_a, dest_a - ph_a - 2);
			patch(S, ch, ph_b, dest_b - ph_b - 2);

		} else if (0 == strcmp(name, "while")) { 
			CK(l.len >= 3, "while requires at least 2 arguments");
			// (while cond body ...)
			// A:
			// cond
			// 0branch ->B
			// body ....
			// redo ->A
			// B:
			// nil   (while loop always returns nil)
			size_t dest_a = ch->bc.len;
			compile_node(S, ch, l.vals[1]);
			chunk_wbc(S, ch, OP_0BRANCH);
			size_t ph_b = placeholder(S, ch);
			for (int i = 2; i < l.len; i++)  {
				compile_node(S, ch, l.vals[i]);
				chunk_wbc(S, ch, OP_DROP);
			}
			chunk_wbc(S, ch, OP_REDO);
			size_t ph_a = placeholder(S, ch);
			size_t dest_b = ch->bc.len;
			chunk_wbc(S, ch, OP_NIL);

			patch(S, ch, ph_a, ph_a - dest_a + 2);
			patch(S, ch, ph_b, dest_b - ph_b - 2);

		} else {
				
			CK(l.len == 3, "can only compile binary ops");
			char opchar = l.vals[0].as.str[0];
			Op op;
			switch (opchar) {
			#define OP(char, code) case char: op = code; break;
				OP('+', OP_ADD)
				OP('-', OP_SUB)
				OP('*', OP_MUL)
				OP('/', OP_DIV)
				OP('=', OP_EQU)
				OP('<', OP_CMP)
				OP('%', OP_MOD)
			#undef OP
				default:
					printf("unkown op %s\n",l.vals[0].as.str);
					exit(1);
					break;
			}
			compile_node(S, ch, l.vals[1]);
			compile_node(S, ch, l.vals[2]);
			chunk_wbc(S, ch, op);
		}
		#undef CK
	}
	}
}


int main() {
	State st = state_new();
	State *S = &st;
	Thread th = thread_new(S);
	st.th = &th;
	Chunk ch = chunk_new(S);
	th.ch = &ch;

	char n1[] = "foo";
	char n2[] = "bar";
	char n3[] = "baz";
	ObjString *o1 = objstring_copy(S, n1, 3);
	ObjString *o2 = objstring_copy(S, n2, 3);
	ObjString *o3 = objstring_copy(S, n3, 3);

	ht_put(S, &st.globals, o1, VAL_NUM(69)); 
	ht_put(S, &st.globals, o2, VAL_NUM(2)); 
	ht_put(S, &st.globals, o3, VAL_NUM(3)); 

	AstNode an = read();
	compile_node(S, &ch, an);

	chunk_wbc(S, &ch, OP_PRINT);
	chunk_wbc(S, &ch, OP_RET);

	return runvm(S);
}