USING: kernel math math.order combinators combinators.extras generalizations math.bitwise accessors sequences arrays ;
USING: flac.format flac.stream ;
USING: prettyprint ;

IN: flac.decoder

SYMBOL: current-flac-output

: decode-block-size ( n -- n )
    dup
    {
        { [ 0b0000 = ]               [ drop reserved-block-size ] }
        { [ 0b0001 = ]               [ drop 192 ] }
        { [ 0b0010 0b0101 between? ] [ 2 - 2^ 567 * ] }
        { [ 0b0110 = ]               [ drop 8 flac-read 1 + ] }
        { [ 0b0111 = ]               [ drop 16 flac-read 1 + ] }
        { [ 0b1000 0b1111 between? ] [ 8 - 2^ 256 * ] }
    } cond-case ;

: decode-sample-rate ( n -- n )
    {
        { 0b0000 [ "TODO: GET FROM STREAMINFO" ] }
        { 0b0001 [ 88200 ] }
        { 0b0010 [ 17640 ] }
        { 0b0011 [ 19200 ] }
        { 0b0100 [ 8000 ] }
        { 0b0101 [ 16000 ] }
        { 0b0110 [ 22050 ] }
        { 0b0111 [ 24000 ] }
        { 0b1000 [ 32000 ] }
        { 0b1001 [ 44100 ] }
        { 0b1010 [ 48000 ] }
        { 0b1011 [ 96000 ] }
        { 0b1100 [ 8 flac-read 1000 * ] } ! sample rate in kHz
        { 0b1101 [ 16 flac-read ] }       ! sample rate in Hz
        { 0b1110 [ 16 flac-read 10 * ] }  ! sample rate in tens of Hz
        { 0b1111 [ invalid-sample-rate ] }
    } case ;

: decode-channel-assignment ( n -- channel-assignment )
    {
        { [ 0b0000 0b0111 between? ] [ 0 ] }
        { [ 0b1000 = ]               [ 1 ] }
        { [ 0b1001 = ]               [ 2 ] }
        { [ 0b1010 = ]               [ 3 ] }
        [ reserved-channel-assignment ]
    } cond-case <flac-channel-assignment> ;

: decode-bits-per-sample ( stream-info n -- n )
    {
        { 0b000 [ 0 ] }
        { 0b001 [ 8 ] }
        { 0b010 [ 12 ] }
        { 0b011 [ reserved-sample-size ] }
        { 0b100 [ 16 ] }
        { 0b101 [ 20 ] }
        { 0b110 [ 24 ] }
        { 0b111 [ reserved-sample-size ] }
    } case
    dup 0 = [ drop bits-per-sample>> ] [ nip ] if ;

: read/assert-frame-sync-code ( -- )
    15 flac-read 0b111111111111100 = [ sync-code-error ] unless ;

: read-flac-frame-header ( stream-info -- frame-header )
    [
        read/assert-frame-sync-code
        1 flac-read <flac-frame-blocking-strategy>
        4 flac-read ! blocksize code
        4 flac-read ! sample rate code
        4 flac-read decode-channel-assignment
    ] dip
    3 flac-read decode-bits-per-sample
    1 flac-read drop ! ignore magic sync for now
    flac-read-coded-number
    ! decoding blocksize/samplerate potentially reads from end of header
    [ decode-block-size ] 4dip
    [ decode-sample-rate ] 3dip
    8 flac-read
    flac-frame-header boa ;

: read-flac-subframe-wasted-bits ( -- k )
    1 flac-read 1 = [ 0 [ 1 + 1 flac-read 0 = ] loop ] [ 0 ] if ;

: read-flac-subframe-constant ( blocksize bps -- samples )
     flac-read-int <repetition> [  ] map ;

: read-flac-subframe-verbatim ( blocksize bps -- samples )
     <repetition> [ flac-read-int ] map ;

: adjust-wasted-bits ( wasted-bits samples -- samples' )
    [ swap shift ] with map! ;

: read-residual-coding-method-type ( -- coding-method param-bits param-escape )
    2 flac-read dup
    2 > [ reserved-residual-coding-type ] when
    <flac-entropy-coding-method-type>
    dup entropy-coding-partitioned-rice =  [ 4 0xf ] [ 5 0x1f ] if ;

: read-partition-order/count ( -- partition-order partitions )
    4 flac-read dup 2^ ;

! TODO: even with locals this is pretty gnarly
:: read-residuals ( blocksize predictor-order -- residuals )
    read-residual-coding-method-type :> ( coding-type parameter-bits escape-parameter )
    read-partition-order/count :> ( partition-order partitions )
    blocksize partition-order neg shift :> partition-samples
    {  } :> residuals!

    partitions <iota>
    [| partition |
     parameter-bits flac-read :> rice-parameter
     rice-parameter escape-parameter <
     [
         partition 0 = [ partition-samples predictor-order - ] [ partition-samples ] if <iota>
         [ drop residuals rice-parameter flac-read-rice-signed-int suffix residuals! ] each
     ]
     [
            5 flac-read :> num-bits
            partition-samples partition 0 = [ predictor-order ] [ 0 ] if - <iota>
            [| order |
             residuals num-bits 0 = [ 0 suffix ] [ num-bits flac-read-int suffix ] if residuals!
            ] each
        ] if
    ] each
    residuals ;

: fixed-coefficients ( -- coefficients ) { { } { 1 } { 2 -1 } { 3 -3 1 }  { 4 -6 4 1 } } ;

: read-warmup-samples ( sample-depth order -- samples )
      swap <repetition> [ flac-read-int ] map ;

! TODO: even with locals this is also gnarly
:: restore-linear-prediction ( residuals warmup coefficients quantization-level -- samples )
    coefficients length :> order
    residuals warmup
    [| samples residual |
     samples

     residual

     coefficients
     samples order tail*
     0
     [ * + ] 2reduce

     quantization-level neg shift
     +

     suffix

    ] reduce ;

:: read-flac-subframe-fixed ( blocksize sample-depth order -- samples )
    sample-depth order read-warmup-samples :> warmup
    blocksize order read-residuals :> residuals
    order fixed-coefficients nth :> coefficients
    residuals warmup coefficients 0 restore-linear-prediction ;

: read-qlp-shift ( -- quantization-level )
    5 flac-read ;

: read-qlp-coefficient-precision ( -- precision )
    4 flac-read 1 + ;

: read-lpc-coefficients ( order precision -- coefficients )
    <repetition> [ flac-read-int ] map ;

:: read-flac-subframe-lpc ( blocksize sample-depth order -- samples )
    sample-depth order read-warmup-samples :> warmup
    read-qlp-coefficient-precision :> precision
    read-qlp-shift :> qlp-shift
    order precision read-lpc-coefficients reverse :> coefficients
    blocksize order read-residuals :> residuals
    residuals warmup coefficients qlp-shift restore-linear-prediction ;

! 000000 constant
! 000001 verbatim
! 00001x reserved
! 0001xx reserved
! 001xxx if xxx <= 4 fixed, xxx = order ; else reserved
! 01xxxx reserved
! 1xxxxx lpc
: read-flac-subframe-type ( -- subframe-type order )
    6 flac-read dup
    {
        { [ 0b000000 = ] [ drop f subframe-type-constant ] }
        { [ 0b000001 = ] [ drop f subframe-type-verbatim ] }
        { [ 0b001000 0b001111 between? ] [ 2 0 bit-range subframe-type-fixed ] }
        { [ 0b100000 0b111111 between? ] [ 4 0 bit-range 1 + subframe-type-lpc ] }
        [ drop reserved-subframe-type ]
    } cond-case swap ;

: read/assert-flac-subframe-sync ( -- )
    1 flac-read 1 = [ invalid-subframe-sync ] when ;

: read-flac-subframe-header ( -- subframe-header )
    read/assert-flac-subframe-sync
    read-flac-subframe-type
    read-flac-subframe-wasted-bits
    flac-subframe-header boa ;

: calculate-sample-depth ( bps wasted-bits channel-assignment channel -- sample-depth )
    [ - ] 2dip swap
    {
        { channel-assignment-left  [ 1 = [ 1 ] [ 0 ] if ] }
        { channel-assignment-right [ 0 = [ 1 ] [ 0 ] if ] }
        { channel-assignment-mid   [ 1 = [ 1 ] [ 0 ] if ] }
        [ 2drop 0 ]
    } case + ;

: stereo-decorrelation ( samples channel-assignment -- samples' )
    {
        { channel-assignment-independent [  ]  } ! do nothing
        {
            channel-assignment-left
            [ [ first ] [ first ] [ second ] tri [ - ] 2map 2array ]
        }
        {
            channel-assignment-right
            [ [ second ] [ first ] [ second ] tri [ + ] 2map swap 2array ]
        }
        {
            channel-assignment-mid
            [
                [ first ] [ second ] bi
                { {  } {  } }
                [ [ over ] dip [ [ first ] dip suffix ] [ [ second ] dip suffix ] 2bi* 2array ] 2reduce
            ]
        }
    } case ;

:: read-flac-subframe ( frame-header channel -- samples )
    read-flac-subframe-header :> subframe-header
    subframe-header wasted-bits>> :> wasted-bits
    subframe-header subframe-type>> :> subframe-type
    subframe-header predictor-order>> :> predictor-order
    frame-header bits-per-sample>> :> bps
    frame-header blocksize>> :> blocksize
    frame-header channel-assignment>> :> channel-assignment
    bps wasted-bits channel-assignment channel calculate-sample-depth :> sample-depth

    subframe-type
    {
        { subframe-type-constant [ blocksize sample-depth read-flac-subframe-constant ] }
        { subframe-type-verbatim [ blocksize sample-depth read-flac-subframe-verbatim ] }
        { subframe-type-fixed    [ blocksize sample-depth predictor-order read-flac-subframe-fixed ] }
        { subframe-type-lpc      [ blocksize sample-depth predictor-order read-flac-subframe-lpc   ] }
    } case :> samples!

    wasted-bits samples adjust-wasted-bits ;

: read-flac-subframes ( frame-header channels -- samples )
    [ dup channel-assignment>> swap ] dip
    <iota> [ read-flac-subframe ] with map
    swap stereo-decorrelation ;
!
: read-flac-frame-footer ( -- frame-footer )
     16 flac-read flac-frame-footer boa ;

: read-flac-frame ( stream-info -- frame )
    [ read-flac-frame-header dup ] [ channels>> ] bi
    read-flac-subframes
    flac-align-to-byte
    read-flac-frame-footer
    flac-frame boa ;