from nmigen import *
from nmigen.utils import *
from nmigen.asserts import *

from rtio.sed import layouts

__all__ = ["latency", "OutputNetwork"]

# Based on: https://github.com/Bekbolatov/SortingNetworks/blob/master/src/main/js/gr.js
def boms_get_partner(n, l, p):
    if p == 1:
        return n ^ (1 << (l - 1))
    scale = 1 << (l - p)
    box = 1 << p
    sn = n//scale - n//scale//box*box
    if sn == 0 or sn == (box - 1):
        return n
    if (sn % 2) == 0:
        return n - scale
    return n + scale

def boms_steps_pairs(lane_count):
    d = log2_int(lane_count)
    steps = []
    for l in range(1, d+1):
        for p in range(1, l+1):
            pairs = []
            for n in range(2**d):
                partner = boms_get_partner(n, l, p)
                if partner != n:
                    if partner > n:
                        pair = (n, partner)
                    else:
                        pair = (partner, n)
                    if pair not in pairs:
                        pairs.append(pair)
            steps.append(pairs)
    return steps

def latency(lane_count):
    d = log2_int(lane_count)
    return sum(l for l in range(1, d+1))

def cmp_wrap(a, b):
    return Mux((a[-2] == a[-1]) & (b[-2] == b[-1]) & (a[-1] != b[-1]), a[-1], a < b)

class OutputNetwork(Elaboratable):
    def __init__(self, lane_count, seqn_width, layout_payload):
        self.lane_count = lane_count
        self.seqn_width = seqn_width
        self.layout_payload = layout_payload

        self.steps = boms_steps_pairs(lane_count)
        self.network = [[Record(layouts.output_network_node(seqn_width, layout_payload)) for _ in range(lane_count)] for _ in range(len(self.steps) + 1)]
        for i in range(1, len(self.steps) + 1):
            for rec in self.network[i]:
                rec.seqn.reset_less = True
                rec.replace_occured.reset_less = True
                rec.nondata_replace_occured.reset_less = True
                for field, _ in layout_payload:
                    getattr(rec.payload, field).reset_less = True
        self.input = self.network[0]
        self.output = self.network[-1]

    def elaborate(self, platform):
        m = Module()

        for i in range(len(self.steps)):
            for node1, node2 in self.steps[i]:
                nondata_difference = Signal()
                for field, _ in self.layout_payload:
                    if field != 'data':
                        f1 = getattr(self.network[i][node1].payload, field)
                        f2 = getattr(self.network[i][node2].payload, field)
                        with m.If(f1 != f2):
                            m.d.comb += nondata_difference.eq(1)

                k1 = Cat(self.network[i][node1].payload.channel, ~self.network[i][node1].valid)
                k2 = Cat(self.network[i][node2].payload.channel, ~self.network[i][node2].valid)
                with m.If(k1 == k2):
                    with m.If(cmp_wrap(self.network[i][node1].seqn, self.network[i][node2].seqn)):
                        m.d.sync += self.network[i + 1][node1].eq(self.network[i][node2])
                        m.d.sync += self.network[i + 1][node2].eq(self.network[i][node1])
                    with m.Else():
                        m.d.sync += self.network[i + 1][node1].eq(self.network[i][node1])
                        m.d.sync += self.network[i + 1][node2].eq(self.network[i][node2])
                    m.d.sync += self.network[i + 1][node1].replace_occured.eq(1)
                    m.d.sync += self.network[i + 1][node1].nondata_replace_occured.eq(nondata_difference)
                    m.d.sync += self.network[i + 1][node2].valid.eq(0)
                with m.Elif(k1 < k2):
                    m.d.sync += self.network[i + 1][node1].eq(self.network[i][node1])
                    m.d.sync += self.network[i + 1][node2].eq(self.network[i][node2])
                with m.Else():
                    m.d.sync += self.network[i + 1][node1].eq(self.network[i][node2])
                    m.d.sync += self.network[i + 1][node2].eq(self.network[i][node1])
            
            unchanged = list(range(self.lane_count))
            for node1, node2 in self.steps[i]:
                unchanged.remove(node1)
                unchanged.remove(node2)
            for node in unchanged:
                m.d.sync += self.network[i + 1][node].eq(self.network[i][node])

        return m