#include "globals.h"
#include "reader-dre-st20.h"

#define IPTR 0
#define WPTR 1
#define AREG 2
#define BREG 3
#define CREG 4

#define FLASHS 0x7FE00000
#define FLASHE 0x7FFFFFFF
#define RAMS   0x40000000
#define RAME   0x401FFFFF
#define IRAMS  0x80000000
#define IRAME  0x800017FF

#define ERR_ILL_OP -1
#define ERR_CNT    -2
#define FLA_ERR    -3
#define RAM_ERR    -4

// ----------------------------------------------------------------

#define STACKMAX  16
#define STACKMASK (STACKMAX-1)

typedef struct
{
	uint32_t Iptr, Wptr;
	uint8_t *flash, *ram;
	uint32_t flashSize, ramSize;
	int sptr, stack[STACKMAX];
	uint8_t iram[0x1800];
	int invalid;
} st20_context_t;

static bool st20_set_flash(st20_context_t *ctx, uint8_t *m, uint32_t len);
static bool st20_set_ram(st20_context_t *ctx, uint8_t *m, uint32_t len);
static void st20_init(st20_context_t *ctx, uint32_t IPtr, uint32_t WPtr);
static void st20_free(st20_context_t *ctx);

static void st20_set_call_frame(st20_context_t *ctx, uint32_t raddr, int p1, int p2, int p3);

static uint32_t st20_get_reg(st20_context_t *ctx, int reg);
static void st20_set_reg(st20_context_t *ctx, int reg, uint32_t val);
static uint8_t st20_rbyte(st20_context_t *ctx, uint32_t off);
static void st20_wbyte(st20_context_t *ctx, uint32_t off, uint8_t val);
static uint32_t st20_rword(st20_context_t *ctx, uint32_t off);
static void st20_wword(st20_context_t *ctx, uint32_t off, uint32_t val);

#define INVALID_VALUE 0xCC
#define ERRORVAL      0xDEADBEEF

#define MININT        0x7FFFFFFF
#define MOSTPOS       0x7FFFFFFF
#define MOSTNEG       0x80000000

#define POP() ctx->stack[(ctx->sptr++)&STACKMASK]
#define PUSH(v) do { int32_t __v=(v); ctx->stack[(--ctx->sptr)&STACKMASK]=__v; } while(0)
#define DROP(n) ctx->sptr+=n

#define AAA ctx->stack[ctx->sptr&STACKMASK]
#define BBB ctx->stack[(ctx->sptr+1)&STACKMASK]
#define CCC ctx->stack[(ctx->sptr+2)&STACKMASK]

#define GET_OP() operand|=op1&0x0F
#define CLEAR_OP() operand=0
#define JUMP(x) ctx->Iptr+=(x)
#define POP64() ({ uint32_t __b=POP(); ((uint64_t)POP()<<32)|__b; })
#define PUSHPOP(op,val) do { int32_t __a=val; AAA op##= (__a); } while(0)

#define RB(off) st20_rbyte(ctx, off)
#define RW(off) st20_rword(ctx, off)
#define WW(off,val) st20_wword(ctx, off, val)

static uint32_t st20_get_reg(st20_context_t *ctx, int32_t reg)
{
	switch(reg)
	{
		case IPTR: return ctx->Iptr;
		case WPTR: return ctx->Wptr;
		case AREG: return AAA;
		case BREG: return BBB;
		case CREG: return CCC;
	}
	return 0;
}

static void st20_set_reg(st20_context_t *ctx, int32_t reg, uint32_t val)
{
	switch(reg)
	{
		case IPTR: ctx->Iptr = val; return;
		case WPTR: ctx->Wptr = val; return;
		case AREG: AAA=val; return;
		case BREG: BBB=val; return;
		case CREG: CCC=val; return;
	}
}

static uint8_t *st20_addr(st20_context_t *ctx, uint32_t off)
{
	if(off >= FLASHS && off <= FLASHE)
	{
		return &ctx->flash[off - FLASHS];
	}
	else if(off >= RAMS && off <= RAME)
	{
		return &ctx->ram[off - RAMS];
	}
	else if(off >= IRAMS && off <= IRAME)
	{
		return &ctx->iram[off - IRAMS];
	}

	ctx->invalid = ERRORVAL;
	return (uint8_t *) &ctx->invalid;
}

static uint32_t st20_rword(st20_context_t *ctx, uint32_t off)
{
	uint8_t *temp;
	temp = st20_addr(ctx, off);

	return ((temp[3] << 24) | (temp[2] << 16) | (temp[1] << 8) | temp[0]);
}

static uint16_t st20_rshort(st20_context_t *ctx, uint32_t off)
{
	uint8_t *temp;
	temp = st20_addr(ctx, off);

	return ((temp[0] << 8) | temp[1]);
}

static uint8_t st20_rbyte(st20_context_t *ctx, uint32_t off)
{
	return *st20_addr(ctx, off);
}

static void st20_wword(st20_context_t *ctx, uint32_t off, uint32_t val)
{
	uint8_t *temp;
	temp = st20_addr(ctx, off);
	temp[3] = (val >> 24) & 0xFF;
	temp[2] = (val >> 16) & 0xFF;
	temp[1] = (val >> 8) & 0xFF;
	temp[0] = val & 0xFF;
}

static void st20_wbyte(st20_context_t *ctx, uint32_t off, uint8_t val)
{
	uint8_t *temp;
	temp = st20_addr(ctx, off);
	temp[0] = val;
}

static int32_t st20_decode(st20_context_t *ctx, int32_t count)
{
	int32_t operand = 0;
	CLEAR_OP();

	while(ctx->Iptr != 0)
	{
		int32_t a, op1 = RB(ctx->Iptr++);
		GET_OP();

		switch(op1 >> 4)
		{
			case 0x0: // j / jump
				JUMP(operand);
				CLEAR_OP();
				break;

			case 0x1: // ldlp
				PUSH(ctx->Wptr + (operand * 4));
				CLEAR_OP();
				break;

			case 0x2: // positive prefix
				operand <<= 4;
				break;

			case 0x3: // ldnl
				AAA=RW(AAA + (operand * 4));
				CLEAR_OP();
				break;

			case 0x4: // ldc
				PUSH(operand);
				CLEAR_OP();
				break;

			case 0x5: // ldnlp
				PUSHPOP(+, operand * 4);
				CLEAR_OP();
				break;

			case 0x6: // negative prefix
				operand = (~operand) << 4;
				break;

			case 0x7: // ldl
				PUSH(RW(ctx->Wptr + (operand * 4)));
				CLEAR_OP();
				break;

			case 0x8: // adc
				PUSHPOP(+, operand);
				CLEAR_OP();
				break;

			case 0x9: // call
				ctx->Wptr -= 16;
				WW(ctx->Wptr, ctx->Iptr); WW(ctx->Wptr + 4, POP()); WW(ctx->Wptr + 8, POP()); WW(ctx->Wptr + 12, POP());
				PUSH(ctx->Iptr);
				JUMP(operand);
				CLEAR_OP();
				break;

			case 0xA: // cj / conditional jump
				if(AAA) { DROP(1); } else { JUMP(operand); }
				CLEAR_OP();
				break;

			case 0xB: // ajw / adjust workspace
				ctx->Wptr += operand * 4;
				CLEAR_OP();
				break;

			case 0xC: // eqc / equals constant
				AAA = (operand == AAA ? 1 : 0);
				CLEAR_OP();
				break;

			case 0xD: // stl
				WW(ctx->Wptr + (operand * 4), POP());
				CLEAR_OP();
				break;

			case 0xE: // stnl
				a = POP(); WW(a + (operand * 4), POP());
				CLEAR_OP();
				break;

			case 0xF: // opr (secondary ins)
				switch(operand)
				{
					case 0x00: a = AAA; AAA = BBB; BBB = a; break;
					case 0x01: AAA = RB(AAA); break;
					case 0x02: PUSHPOP(+, POP()); break;
					case 0x04: PUSHPOP(-, POP()); break;
					case 0x05: PUSHPOP(+, POP()); break;
					case 0x06: a = AAA; AAA = ctx->Iptr; ctx->Iptr = a; break;
					case 0x08: PUSHPOP(*, POP()); break;
					case 0x09: a=POP(); AAA = (AAA > a); break;
					case 0x0A: a=POP(); AAA = a + (AAA * 4); break;
					case 0x0C: PUSHPOP(-, POP()); break;
					case 0x1A: { a = POP(); uint64_t ll = POP64(); PUSH(ll % (uint32_t)a); PUSH(ll / (uint32_t)a); } break;
					case 0x1B: PUSHPOP(+, ctx->Iptr); break;
					case 0x1D: CCC = BBB; BBB = (AAA >= 0 ? 0 : -1); break;
					case 0x1F: PUSHPOP(%, POP()); break;
					case 0x20: ctx->Iptr = RW(ctx->Wptr); ctx->Wptr = ctx->Wptr + 16; break;
					case 0x2C: PUSHPOP(/, POP()); break;
					case 0x30: break;
					case 0x32: AAA =~ AAA; break;
					case 0x33: PUSHPOP(^, POP()); break;
					case 0x34: PUSHPOP(*, 4); break;
					case 0x35: { a = POP(); uint64_t ll = POP64() >> a; PUSH((ll >> 32) & 0xFFFFFFFF); PUSH(ll & 0xFFFFFFFF); } break;
					case 0x36: { a = POP(); uint64_t ll = POP64() << a; PUSH((ll >> 32) & 0xFFFFFFFF); PUSH(ll & 0xFFFFFFFF); } break;
					case 0x3B: a = POP(); st20_wbyte(ctx, a, POP()); break;
					case 0x3F: a = POP(); PUSH(a & 3); PUSH((uint32_t)a >> 2); break;
					case 0x40: a = POP(); AAA = (uint32_t)AAA >> a; break;
					case 0x41: a = POP(); AAA = (uint32_t)AAA << a; break;
					case 0x42: PUSH(MOSTNEG); break;
					case 0x46: PUSHPOP(&, POP()); break;
					case 0x4A: { a = POP(); int32_t b = POP(); int32_t c = POP(); while(a--) st20_wbyte(ctx, b++, st20_rbyte(ctx, c++)); } break;
					case 0x4B: PUSHPOP(|, POP()); break;
					case 0x53: PUSHPOP(*, POP()); break;
					case 0x5A: PUSH(AAA); break;
					case 0x5F: a = POP(); AAA = ((uint32_t)AAA > (uint32_t)a); break;
					case 0x78: { a = POP(); int32_t b = POP(); int32_t bb = 0; while(a--){bb <<= 1; bb |= b & 1; b >>= 1;} PUSH(bb);} break;
					case 0xCA: AAA = st20_rshort(ctx, AAA); break;
					default:
						cs_log("[icg] unknown opcode %X", operand);
						return ERR_ILL_OP;
				}
				CLEAR_OP();
				break;
		}

		if(--count <= 0 && operand == 0)
		{
			return ERR_CNT;
		}
	}
	return 0;
}

static bool st20_set_flash(st20_context_t *ctx, uint8_t *m, uint32_t len)
{
	if (len)
	{
		ctx->flash = (uint8_t *)malloc(len);
		ctx->flashSize = len;
	}
	else
	{
		cs_log("ERROR len!");
		ctx->flashSize = 0;
		return false;
	}

	if (ctx->flash == NULL)
	{
		cs_log("ERROR, malloc!");
		ctx->flashSize = 0;
		return false;
	}
	else
	{
		if(m == NULL)
		{
			memset(ctx->flash, 0, len);
		}
		else
		{
			memcpy(ctx->flash, m, len);
		}
	}

	return true;
}

static bool st20_set_ram(st20_context_t *ctx, uint8_t *m, uint32_t len)
{
	if (len)
	{
		ctx->ram = (uint8_t *)malloc(len);
		ctx->ramSize = len;
	}
	else
	{
		cs_log("ERROR len!");
		ctx->ramSize = 0;
		return false;
	}

	if (ctx->ram == NULL)
	{
		cs_log("ERROR, malloc!");
		ctx->ramSize = 0;
		return false;
	}
	else
	{
		if(m == NULL)
		{
			memset(ctx->ram, 0, len);
		}
		else
		{
			memcpy(ctx->ram, m, len);
		}
	}

	return true;
}

static void st20_init(st20_context_t *ctx, uint32_t IPtr, uint32_t WPtr)
{
	ctx->Wptr = WPtr;
	ctx->Iptr = IPtr;
	memset(ctx->stack, INVALID_VALUE, sizeof(ctx->stack));
	ctx->sptr = STACKMAX - 3;
	memset(ctx->iram, 0, sizeof(ctx->iram));
}

static void st20_free(st20_context_t *ctx)
{
	if(ctx->flashSize)
	{
		free(ctx->flash);
		ctx->flashSize = 0;
	}
	ctx->flash = NULL;

	if(ctx->ramSize)
	{
		free(ctx->ram);
		ctx->ramSize = 0;
	}
	ctx->ram = NULL;
}

static void st20_set_call_frame(st20_context_t *ctx, uint32_t raddr, int32_t p1, int32_t p2, int32_t p3)
{
	ctx->Wptr -= 16;
	st20_wword(ctx, ctx->Wptr, raddr); // RET
	st20_wword(ctx, ctx->Wptr + 4, p1); // Areg
	st20_wword(ctx, ctx->Wptr + 8, p1); // Breg
	st20_wword(ctx, ctx->Wptr + 12, p1); // Creg
	st20_wword(ctx, ctx->Wptr + 16, p2);
	st20_wword(ctx, ctx->Wptr + 20, p3);
	st20_set_reg(ctx, AREG, raddr); // RET
}

int st20_run(uint8_t* snip, uint32_t snip_len, int addr, uint8_t *data, uint16_t overcryptId)
{
	int error = 0, i, n;
	st20_context_t ctx;

	cs_log("[icg] decrypt address = 0x%X, id = %04X", addr, overcryptId);

	cs_log("[icg] CW: %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X ",
			data[0], data[1], data[2], data[3], data[4], data[5], data[6], data[7],
			data[8], data[9], data[10], data[11], data[12], data[13], data[14], data[15]);

	for(n = 0; n < 2; n++)
	{
		memset(&ctx, 0, sizeof(st20_context_t));
		if (!st20_set_ram(&ctx, 0, 0x1000))
		{
			error = RAM_ERR;
			break;
		}
		if (!st20_set_flash(&ctx, snip + 0x48, (int) (snip_len - 0x48)))
		{
			error = FLA_ERR;
			break;
		}
		st20_init(&ctx, FLASHS + addr, RAMS + 0x100);
		st20_set_call_frame(&ctx, 0, RAMS, RAMS, RAMS);

		for(i = 0; i < 8; i++)
		{
			st20_wbyte(&ctx, RAMS + i, data[i + n * 8]);
		}

		if((error = st20_decode(&ctx, 800000)) < 0)
		{
			break;
		}

		cs_log("[icg] cw%d ret = %d, AREG = %X", n + 1, error, st20_get_reg(&ctx, AREG));

		for(i = 0; i < 8; i++)
		{
			data[i + n * 8] = st20_rbyte(&ctx, RAMS + i);
		}
		st20_free(&ctx);
	}

	if(error < 0)
	{
		//in error case ensure free ctx!
		st20_free(&ctx);

		cs_log("[icg] st20 processing failed with error %d", error);
		return 0;
	}

	cs_log("[icg] DW: %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X %02X ",
			data[0], data[1], data[2], data[3], data[4], data[5], data[6], data[7],
			data[8], data[9], data[10], data[11], data[12], data[13], data[14], data[15]);
	return 1;
}
