#!/usr/bin/env ruby

require "scanf"

FREQ_MULT_OFFSET = 0x20
SCALE_LEVEL_OFFSET = 0x40
ATTACK_DECAY_OFFSET = 0x60
SUSTAIN_RELEASE_OFFSET = 0x80
OCTAVE_KEY_LSB_OFFSET = 0xa0
OCTAVE_KEY_MSB_OFFSET = 0xb0
FEEDBACK_OFFSET = 0xc0
WAVEFORM_SELECT_OFFSET = 0xe0

CHANNEL_OPERATORS = [ [ 0x00, 0x03 ],
                      [ 0x01, 0x04 ],
                      [ 0x02, 0x05 ],
                      [ 0x08, 0x0b ],
                      [ 0x09, 0x0c ],
                      [ 0x0a, 0x0d ],
                      [ 0x10, 0x13 ],
                      [ 0x11, 0x14 ],
                      [ 0x12, 0x15 ] ]

def reverse_channels_list
    result = [ -1 ] * 21

    for channel in 0...CHANNEL_OPERATORS.length
        result[CHANNEL_OPERATORS[channel][0]] = channel
        result[CHANNEL_OPERATORS[channel][1]] = channel
    end

    result
end

OPERATOR_TO_CHANNEL = reverse_channels_list

class RegisterWrite

    attr_reader :register, :value

    def initialize(register, value)
        @register = register
        @value = value
    end

    def to_s
        sprintf("%02x: %02x", @register, @value)
    end
end

class MatchPattern
    def initialize(pattern_class, pattern)
        @pattern_class = pattern_class
        @pattern = pattern
    end

    def matches(array, offset)

        # Sanity check

        if offset + length > array.length
            return nil
        end

        # Check that all values in this pattern match

        for i in 0...@pattern.length
            reg_pattern = @pattern[i]
            reg_write = array[offset + i]

            # Is this a write to the expected register?

            expected = reg_pattern[0]
            mask = reg_pattern[1]

            if (reg_write.register & mask) != (expected & mask)
                return nil
            end

            # Optional checking of the value:

            if reg_pattern.length > 2
                expected = reg_pattern[2]
                mask = reg_pattern[3]

                if (reg_write.value & mask) != (expected & mask)
                    return nil
                end
            end
        end

        @pattern_class.new(array[offset,length])
    end

    def length
        @pattern.length
    end
end

class Event
    attr_reader :reg_writes

    def initialize(reg_writes)
        @reg_writes = reg_writes
    end

    # Get a particular register value set in this event:

    def find_value(register)
        for r in @reg_writes
            if register == r.register
                return r.value
            end
        end

        nil
    end
end

# Event to configure a channel:

class ChannelEvent < Event
    def channel
        first_reg = @reg_writes[0].register
        first_reg & 0xf
    end

    def operator_1
        CHANNEL_OPERATORS[channel][0]
    end

    def operator_2
        CHANNEL_OPERATORS[channel][1]
    end
end

# Event to configure a channel, but we are actually only configuring
# a single operator

class OperatorEvent < ChannelEvent
    def channel
        first_reg = @reg_writes[0].register
        operator = first_reg & 0x1f
        OPERATOR_TO_CHANNEL[operator]
    end

    # Operator number - 0 or 1

    def operator_num
        first_reg = @reg_writes[0].register
        operator = first_reg & 0x1f

        if operator == operator_1
            0
        else
            1
        end
    end
end

class InitChannel < OperatorEvent

    GENMIDI_REGS = [ FREQ_MULT_OFFSET, ATTACK_DECAY_OFFSET,
                     SUSTAIN_RELEASE_OFFSET, WAVEFORM_SELECT_OFFSET,
                     SCALE_LEVEL_OFFSET, SCALE_LEVEL_OFFSET ]

    def operator_values(op)
        result = []
        for base in GENMIDI_REGS
            result.push(find_value(base + op))
        end

        result[4] &= 0xc0  # Key scale level
        result[5] &= 0x3f  # Output level

        result
    end

    # Get values in the order that they are stored in the GENMIDI
    # lump.

    def values
        operator_values(operator_1) +
        [ find_value(FEEDBACK_OFFSET + channel) ] +
        operator_values(operator_2)
    end

    # Description of the instrument being loaded:

    def instr_desc
        instr_data = $instruments[values]

        if instr_data == nil
            return "- Unknown instrument"
        end

        result = ""

        for possible in instr_data
            result += "- Instrument ##{possible[:instrument]} " \
                   +  "(#{possible[:name]}) "                   \
                   +  "v#{possible[:voice]}\n"
        end

        result
    end

    def to_s
        stringified = values.map { |val| sprintf("%02x", val) }
        stringified = stringified.join(",")
        "Initializing channel #{channel}: #{stringified}\n" + instr_desc
    end
end

class DetectionSequence < Event
    def to_s
        "Adlib detection sequence"
    end
end

class ScaleLevelChange < OperatorEvent
    SCALE_LEVELS = [
        "no change",
        "3dB/8ve",
        "1.5dB/8ve",
        "6dB/8ve"
    ]

    def to_s
        value = @reg_writes[0].value

        scale_level = (value >> 6) & 0x3
        total_level = (value & 0x3f) * 0.75

        "Scale level change on channel #{channel}, op #{operator_num}: " +
            "#{total_level}dB, #{SCALE_LEVELS[scale_level]}"
    end
end

class KeyOn < ChannelEvent
    def to_s
        value = @reg_writes[0].value | (@reg_writes[1].value << 8)

        octave = (value >> 10) & 0x7
        f_number = value & 0x3ff

        sprintf("Key on, channel %i: octave %i, freq 0x%x",
                channel, octave, f_number)
    end
end

class KeyOff < ChannelEvent
    OPERATOR_TYPE = true

    def to_s
        "Key off, channel #{channel}"
    end
end

class InitialInit < Event
    def to_s
        "Initial initialisation of registers..."
    end
end

# Fallback for if we can't match a pattern:

class BasicRegisterWrite < Event
    def to_s
        "Basic register write: " + @reg_writes[0].to_s
    end
end

# GENMIDI parsing code:

NUM_INSTRUMENTS = 175

def read_instrument(file)
    result = []

    36.times do
        c = file.getc
        result.push(c)
    end

    result
end

# "Flatten" voice data in the way that the Doom code will:

def flatten_voice(voice_data)
    modulating = (voice_data[6] & 0x01) == 0;

    # Voices 1 and 2 (for OPL3)
    voice_data[6] |= 0x30;

    # 2nd op always has level set to max 
    voice_data[12] |= 0x3f;

    # 1st op has level set to max if not modulating
    if !modulating
        voice_data[5] |= 0x3f;
    end
end

# Add a voice to the instruments lookup table.

def add_voice(instruments, voice_data, instr_num, voice_num, name)
    if instruments[voice_data] == nil
        instruments[voice_data] = []
    end

    instruments[voice_data].push({
        :instrument => instr_num,
        :voice => voice_num,
        :name => name
    })
end

def read_genmidi(filename)
    instr_data = []
    instr_names = []

    File.open(filename) do |file|
        header = file.read(8)

        if header != "#OPL_II#"
            raise "Header not found!"
        end

        NUM_INSTRUMENTS.times do
	    data = read_instrument(file)
            instr_data.push(data)
        end

        NUM_INSTRUMENTS.times do
            name = file.read(32).strip
            instr_names.push(name)
        end
    end

    instruments = {}

    for i in 0...NUM_INSTRUMENTS
        dual_voice = (instr_data[i][0] & 0x04) != 0
        voice1 = instr_data[i][4, 13]
        voice2 = instr_data[i][20, 13]

        flatten_voice(voice1)
        flatten_voice(voice2)

        add_voice(instruments, voice1, i, 1, instr_names[i])

        if dual_voice
            add_voice(instruments, voice2, i, 2, instr_names[i])
        end
    end

    instruments
end

def parse_cmdline
    i = 0
    $instruments = {}

    while i < ARGV.length
        if ARGV[i] == "-genmidi"
            $instruments = read_genmidi(ARGV[i + 1])
            i += 1
        end
        i += 1
    end
end

def parse_file(stream)
    register = nil

    result = []

    stream.each_line do |s|
        if s =~ /OPL_write: (\d+), ([0-9a-fA-F]+)/
            reg = $1.to_i
            value = $2.scanf("%x")[0]

            if reg == 0
                register = value
            else
                result.push(RegisterWrite.new(register, value))
            end
        end
    end

    result
end

MATCH_PATTERNS = [
    # Adlib detection sequence:

    MatchPattern.new(DetectionSequence,
                     [ [ 4, 0xff, 0x60, 0xff ],
                       [ 4, 0xff, 0x80, 0xff ],
                       [ 2, 0xff, 0xff, 0xff ],
                       [ 4, 0xff, 0x21, 0xff ],
                       [ 4, 0xff, 0x60, 0xff ],
                       [ 4, 0xff, 0x80, 0xff ] ]),

    # Startup initialisation values:

    MatchPattern.new(InitialInit,
                     [ [ 0x40, 0xe3, 0x3f, 0xff ],
                       [ 0x41, 0xe3, 0x3f, 0xff ],
                       [ 0x42, 0xe3, 0x3f, 0xff ],
                       [ 0x43, 0xe3, 0x3f, 0xff ] ]),

    MatchPattern.new(InitialInit,
                     [ [ 0x00, 0x03, 0x00, 0xff ],
                       [ 0x01, 0x03, 0x00, 0xff ],
                       [ 0x02, 0x03, 0x00, 0xff ],
                       [ 0x03, 0x03, 0x00, 0xff ] ]),

    # Key on

    MatchPattern.new(KeyOn,
                     [ [ OCTAVE_KEY_LSB_OFFSET, 0xf0 ],
                       [ OCTAVE_KEY_MSB_OFFSET, 0xf0, 0x20, 0x20 ]]),

    # Key off
    MatchPattern.new(KeyOff,
                     [ [ OCTAVE_KEY_MSB_OFFSET, 0xf0, 0x20, 0x00 ]]),

    # This pattern occurs when a channel has the registers for its
    # operators initialised.

    MatchPattern.new(InitChannel,
                     [ [SCALE_LEVEL_OFFSET,     0xe0],           # First op
                       [FREQ_MULT_OFFSET,       0xe0],
                       [ATTACK_DECAY_OFFSET,    0xe0],
                       [SUSTAIN_RELEASE_OFFSET, 0xe0],
                       [WAVEFORM_SELECT_OFFSET, 0xe0],

                       [SCALE_LEVEL_OFFSET,     0xe0],           # Second op
                       [FREQ_MULT_OFFSET,       0xe0],
                       [ATTACK_DECAY_OFFSET,    0xe0],
                       [SUSTAIN_RELEASE_OFFSET, 0xe0],
                       [WAVEFORM_SELECT_OFFSET, 0xe0],

                       [FEEDBACK_OFFSET,        0xf0] ]),

    # Scale level change

    MatchPattern.new(ScaleLevelChange,
                     [ [ SCALE_LEVEL_OFFSET,    0xe0 ] ]),

    # Fallback basic register write:

    MatchPattern.new(BasicRegisterWrite, [[0, 0]])
]

parse_cmdline

writes = parse_file($stdin)

offset = 0
parsed = []

channel_in_use = [ false ] * 9
channel_allocate_queue = [ 0, 1, 2, 3, 4, 5, 6, 7, 8 ]

while offset < writes.length
    for pattern in MATCH_PATTERNS
        match = pattern.matches(writes, offset)

        if match != nil
            parsed.push(match)
            offset += pattern.length

            if match.is_a?(KeyOn) and (match.channel >= 0 and match.channel < 9)
                if !channel_in_use[match.channel]
                    expected = channel_allocate_queue[0]
                    channel_allocate_queue = (channel_allocate_queue[1,9] or [])
                    channel_in_use[match.channel] = true
                    puts "expect: #{expected}"
                end
            end
            if match.is_a?(KeyOff) and (match.channel >= 0 and match.channel < 9)
                channel_allocate_queue.push(match.channel)
                channel_in_use[match.channel] = false
            end

            puts match
            for r in match.reg_writes
                puts "\t#{r}"
            end

            break
        end
    end
end