using System;
using System.IO;
using System.Collections.Generic;

using BizHawk.Emulation.Sound;

//http://wiki.nesdev.com/w/index.php/APU_Mixer_Emulation
//http://wiki.nesdev.com/w/index.php/APU
//http://wiki.nesdev.com/w/index.php/APU_Pulse
//sequencer ref: http://wiki.nesdev.com/w/index.php/APU_Frame_Counter

namespace BizHawk.Emulation.Consoles.Nintendo
{

	partial class NES
	{
		public class APU : ISoundProvider
		{
			public static bool CFG_USE_METASPU = true;
			public static bool CFG_DECLICK = true;

			NES nes;
			public APU(NES nes)
			{
				this.nes = nes;
			}

			static int[] LENGTH_TABLE = { 10, 254, 20, 2, 40, 4, 80, 6, 160, 8, 60, 10, 14, 12, 26, 14, 12, 16, 24, 18, 48, 20, 96, 22, 192, 24, 72, 26, 16, 28, 32, 30 };
			static byte[,] PULSE_DUTY = {
				{0,1,0,0,0,0,0,0}, //(12.5%)
				{0,1,1,0,0,0,0,0}, //(25%)
				{0,1,1,1,1,0,0,0}, //(50%)
				{1,0,0,1,1,1,1,1}, //(25% negated (75%))
			};
			static byte[] TRIANGLE_TABLE = 
			{
				15, 14, 13, 12, 11, 10,  9,  8,  7,  6,  5,  4,  3,  2,  1,  0,
 				0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15
			};

	
			class PulseUnit
			{
				public PulseUnit(int unit) { this.unit = unit; }
				public int unit; 

				//reg0
				int duty_cnt, env_loop, env_constant, env_cnt_value;
				//reg1
				int sweep_en, sweep_period, negate, shiftcount;
				//reg2/3
				int len_cnt;
				int timer_raw_reload_value, timer_reload_value;

				//from other apu regs
				public int lenctr_en;

				public void WriteReg(int addr, byte val)
				{
					//Console.WriteLine("write pulse {0:X} {1:X}", addr, val);
					switch(addr)
					{
						case 0:
							env_cnt_value = val & 0xF;
							env_constant = (val >> 4) & 1;
							env_loop = (val >> 5) & 1;
							duty_cnt = (val >> 6) & 3;
							break;
						case 1:
							shiftcount = val & 7;
							negate = (val >> 3) & 1;
							sweep_period = (val >> 4) & 7;
							sweep_en = (val >> 7) & 1;
							break;
						case 2:
							timer_reload_value = (timer_reload_value & ~0xFF) | val;
							calc_sweep_unit();
							break;
						case 3:
							len_cnt = LENGTH_TABLE[(val >> 3) & 0x1F];
							timer_reload_value = (timer_reload_value & 0xFF) | ((val & 0x07) << 8);
							timer_raw_reload_value = timer_reload_value * 2;
							duty_step = 0;
							timer_counter = timer_raw_reload_value;
							calc_sweep_unit();
							env_start_flag = 1;
							//serves as a useful note-on diagnostic
							//Console.WriteLine("{0} timer_reload_value: {1}", unit, timer_reload_value);
							break;
					}
				}

				int swp_val_result;
				bool swp_silence;
				int duty_step;
				int timer_counter;
				public int sample;

				int env_start_flag, env_divider, env_counter, env_output;

				void calc_sweep_unit()
				{
					//1's complement for chan 0, 2's complement if chan 1
					if (negate == 1) //check to see if negate is on
						swp_val_result = ~swp_val_result + unit;
					//add with the shifter chan
					swp_val_result += timer_reload_value;

					if ((timer_reload_value < 8) ||
						 ((swp_val_result > 0x7FF) && (negate==0)))
						swp_silence = true; //silence
					else
						swp_silence = false; //don't silence

				}

				public void clock_length_and_sweep()
				{
					//(as well as length counter)
					if(sweep_en==1)
						timer_raw_reload_value = swp_val_result & 0x7FF;
				}

				public void clock_env()
				{
					if (env_start_flag == 1)
					{
						env_start_flag = 0;
						env_divider = (env_cnt_value + 1);
						env_counter = 15;
					}
					else
					{
						env_divider--;
						if (env_divider == 0)
						{
							env_divider = (env_cnt_value + 1);
							if (env_counter == 0)
							{
								if (env_loop == 1)
								{
									env_counter = 15;
								}
							}
							else env_counter--;
						}
					}
					if (env_constant == 1)
						env_output = env_cnt_value;
					else env_output = env_counter;
				}

				public void Run()
				{
					//sweep units are figured out during memory writes to the regs
					//that set the timer, length counter are figured out in the
					//writes and frame counter, and envelope is set through the memory
					//regs also, so we just need to deal with the timer and sequencer here

					timer_counter--;
					if (timer_counter == 0)
					{
						duty_step = (duty_step + 1) & 7;
						//reload timer
						timer_counter = timer_raw_reload_value + 2;
					}
					if (PULSE_DUTY[duty_cnt, duty_step] == 1) //we are outputting something
					{
						sample = env_output;

						if (swp_silence)
							sample = 0;

						//if (len_cnt==0) //length counter is 0
						//    sample = 0; //silenced
					}
					else
						sample = 0; //duty cycle is 0, silenced.

				}
			}

			class TriangleUnit
			{
				//reg0
				int linear_counter_reload, control_flag;
				//reg1 (n/a)
				//reg2/3
				int timer_cnt, length_counter_load, halt_flag;

				public void WriteReg(int addr, byte val)
				{
					switch (addr)
					{
						case 0:
							linear_counter_reload = (val & 0x7F);
							control_flag = (val >> 7) & 1;
							break;
						case 1: break;
						case 2:
							timer_cnt = (timer_cnt & ~0xFF) | val;
							break;
						case 3:
							timer_cnt = (timer_cnt & 0xFF) | ((val & 0x7) << 8);
							timer_cnt_reload = timer_cnt + 1;
							length_counter_load = (val>>3)&0x1F;
							halt_flag = 1;
							break;
					}
				}

				int linear_counter, timer, timer_cnt_reload;
				int seq;
				public int sample;

				public void Run()
				{
					//when clocked by timer
					//seq steps forward
					//except when linear counter or
					//length counter is 0

					bool en = length_counter_load != 0 && linear_counter != 0;

					//length counter and linear counter 
					//is clocked in frame counter.
					if (en)
					{
						timer--;
						if (timer == 0)
						{
							seq = (seq + 1) & 0x1F;
							timer = timer_cnt_reload;
						}
						if(CFG_DECLICK)
							sample = TRIANGLE_TABLE[(seq+8)&0x1F];
						else
							sample = TRIANGLE_TABLE[seq];
					}
					else
						sample = 0;
				}

				
				public void clock_length_and_sweep()
				{
				}

				public void clock_linear_counter()
				{
				//	Console.WriteLine("linear_counter: {0}", linear_counter);
					if (halt_flag == 1)
					{
						timer = timer_cnt_reload;
						linear_counter = linear_counter_reload;
					}
					else if (linear_counter != 0)
					{
						linear_counter--;
					}
					if (control_flag == 0)
					{
						halt_flag = 0;
					}
				}
			}


			PulseUnit[] pulse = { new PulseUnit(0), new PulseUnit(1) };
			TriangleUnit triangle = new TriangleUnit();

			int sequencer_counter, sequencer_step, sequencer_mode, sequencer_irq_inhibit, sequencer_irq_flag;
			void sequencer_reset()
			{
				sequencer_counter = 0;
				sequencer_step = 1;
				if(sequencer_mode == 1) sequencer_check();
			}

			//21477272 master clock
			//1789772 cpu clock (master / 12)
			//240 apu clock (master / 89490) = (cpu / 7457)
			void sequencer_tick()
			{
				sequencer_counter++;
				//this figure is not valid for PAL. it must be recalculated
				if (sequencer_counter != 7457) return;
				sequencer_counter = 0;
				sequencer_step++;
				sequencer_check();
			}

			void sequencer_check()
			{
				switch (sequencer_mode)
				{
					case 0: //4-step
						pulse[0].clock_env();
						pulse[1].clock_env();
						triangle.clock_linear_counter();
						if (sequencer_step == 2 || sequencer_step == 4)
						{
							pulse[0].clock_length_and_sweep();
							pulse[1].clock_length_and_sweep();
							triangle.clock_length_and_sweep();
						}
						if (sequencer_step == 4)
						{
							if (sequencer_irq_inhibit == 0)
							{
								sequencer_irq_flag = 1;
								//nes.cpu.Interrupt = true;
								//Console.WriteLine("APU trigger IRQ (cpu needs implementation)");
							}
							sequencer_step = 0;
						}
						break;
					case 1: //5-step
						if (sequencer_step != 5)
						{
							pulse[0].clock_env();
							pulse[1].clock_env();
							triangle.clock_linear_counter();
						}
						if (sequencer_step == 1 || sequencer_step == 3)
						{
							pulse[0].clock_length_and_sweep();
							pulse[1].clock_length_and_sweep();
							triangle.clock_length_and_sweep();
						}
						if (sequencer_step == 5)
							sequencer_step = 0;
						break;
				}
			}


			public void WriteReg(int addr, byte val)
			{
				switch (addr)
				{
					case 0x4000: case 0x4001: case 0x4002: case 0x4003:
						pulse[0].WriteReg(addr - 0x4000, val);
						break;
					case 0x4004: case 0x4005: case 0x4006: case 0x4007:
						pulse[1].WriteReg(addr - 0x4004, val);
						break;
					case 0x4008: case 0x4009: case 0x400A: case 0x400B:
						triangle.WriteReg(addr - 0x4008, val);
						break;
					case 0x4015:
						pulse[0].lenctr_en = (val & 1);
						pulse[1].lenctr_en = ((val>>1) & 1);
						break;
					case 0x4017:
						sequencer_mode = (val>>7)&1;
						if(((val>>6)&1)==1)
							sequencer_irq_inhibit = 0;
						sequencer_reset();
						break;
				}
			}

			public byte ReadReg(int addr)
			{
				switch (addr)
				{
					default:
						return 0x00;
				}
			}

			public void Run(int cycles)
			{
				for (int i = 0; i < cycles; i++)
					RunOne();
			}

			void RunOne()
			{
				pulse[0].Run();
				pulse[1].Run();
				triangle.Run();

				int mix = 0;
				mix += pulse[0].sample;
				mix += pulse[1].sample;
				mix += triangle.sample;

				EmitSample(mix);

				sequencer_tick();

				//since the units run concurrently, the APU frame sequencer 
				//is ran last because
				//it can change the ouput values of the pulse/triangle channels, 
				//we want the
				//changes to affect it on the *next* cycle.
			}

			double accumulate;
			double timer;
			Queue<int> squeue = new Queue<int>();
			int last_hwsamp;
			void EmitSample(int samp)
			{
				int this_samp = samp;
				const double kMixRate = 44100.0/1789772.0;
				const double kInvMixRate = (1 / kMixRate);
				timer += kMixRate;
				accumulate += samp;
				if (timer <= 1)
					return;

				accumulate -= samp;
				timer -= 1;
				double ratio = (timer / kMixRate);
				double fractional = (this_samp - last_hwsamp) * ratio;
				double factional_remainder = (this_samp - last_hwsamp) * (1-ratio);
				accumulate += fractional;

				accumulate *= 600;
				int outsamp = (int)(accumulate / kInvMixRate);
				if (CFG_USE_METASPU)
					metaspu.buffer.enqueue_sample((short)outsamp, (short)outsamp);
				else squeue.Enqueue(outsamp);
				accumulate = factional_remainder;

				last_hwsamp = this_samp;
			}

			MetaspuSoundProvider metaspu = new MetaspuSoundProvider(ESynchMethod.ESynchMethod_Z);

			void ISoundProvider.GetSamples(short[] samples)
			{
				if(CFG_USE_METASPU)
					metaspu.GetSamples(samples);
				else
					MyGetSamples(samples);
			}

			//static BinaryWriter bw = new BinaryWriter(File.OpenWrite("d:\\out.raw"));
			void MyGetSamples(short[] samples)
			{
				//Console.WriteLine("a: {0} with todo: {1}",squeue.Count,samples.Length/2);

				for (int i = 0; i < samples.Length/2; i++)
				{
					int samp = 0;
					if (squeue.Count != 0)
						samp = squeue.Dequeue();
					
					samples[i*2+0] = (short)(samp);
					samples[i*2+1] = (short)(samp);
					//bw.Write((short)samp);
				}
			}

		} //class APU


	}

}