"""Draws DAG in ASCII."""

import logging
import math
import os
import pydoc
import sys

from grandalf.graphs import Edge
from grandalf.graphs import Graph
from grandalf.graphs import Vertex
from grandalf.layouts import SugiyamaLayout
from grandalf.routing import EdgeViewer
from grandalf.routing import route_with_lines

from dvc.env import DVC_PAGER
from dvc.utils import format_link

logger = logging.getLogger(__name__)


DEFAULT_PAGER = "less"
DEFAULT_PAGER_FORMATTED = "{} --chop-long-lines --clear-screen".format(
    DEFAULT_PAGER
)


def make_pager(cmd):
    def pager(text):
        return pydoc.tempfilepager(pydoc.plain(text), cmd)

    return pager


def find_pager():
    if not sys.stdout.isatty():
        return pydoc.plainpager

    env_pager = os.getenv(DVC_PAGER)
    if env_pager:
        return make_pager(env_pager)

    if os.system("({}) 2>{}".format(DEFAULT_PAGER, os.devnull)) == 0:
        return make_pager(DEFAULT_PAGER_FORMATTED)

    logger.warning(
        "Unable to find `less` in the PATH. Check out "
        "{} for more info.".format(
            format_link("https://man.dvc.org/pipeline/show")
        )
    )
    return pydoc.plainpager


class VertexViewer(object):
    """Class to define vertex box boundaries that will be accounted for during
    graph building by grandalf.

    Args:
        name (str): name of the vertex.
    """

    HEIGHT = 3  # top and bottom box edges + text

    def __init__(self, name):
        # pylint: disable=invalid-name
        self._h = self.HEIGHT  # top and bottom box edges + text
        self._w = len(name) + 2  # right and left bottom edges + text

    @property
    def h(self):  # pylint: disable=invalid-name
        """Height of the box."""
        return self._h

    @property
    def w(self):  # pylint: disable=invalid-name
        """Width of the box."""
        return self._w


class AsciiCanvas(object):
    """Class for drawing in ASCII.

    Args:
        cols (int): number of columns in the canvas. Should be > 1.
        lines (int): number of lines in the canvas. Should be > 1.
    """

    TIMEOUT = 10

    def __init__(self, cols, lines):
        assert cols > 1
        assert lines > 1

        self.cols = cols
        self.lines = lines

        self.canvas = [[" "] * cols for line in range(lines)]

    def draw(self):
        """Draws ASCII canvas on the screen."""
        pager = find_pager()
        lines = map("".join, self.canvas)
        joined_lines = os.linesep.join(lines)
        pager(joined_lines)

    def point(self, x, y, char):
        """Create a point on ASCII canvas.

        Args:
            x (int): x coordinate. Should be >= 0 and < number of columns in
                the canvas.
            y (int): y coordinate. Should be >= 0 an < number of lines in the
                canvas.
            char (str): character to place in the specified point on the
                canvas.
        """
        assert len(char) == 1
        assert x >= 0
        assert x < self.cols
        assert y >= 0
        assert y < self.lines

        self.canvas[y][x] = char

    def line(self, x0, y0, x1, y1, char):
        """Create a line on ASCII canvas.

        Args:
            x0 (int): x coordinate where the line should start.
            y0 (int): y coordinate where the line should start.
            x1 (int): x coordinate where the line should end.
            y1 (int): y coordinate where the line should end.
            char (str): character to draw the line with.
        """
        # pylint: disable=too-many-arguments, too-many-branches
        if x0 > x1:
            x1, x0 = x0, x1
            y1, y0 = y0, y1

        dx = x1 - x0
        dy = y1 - y0

        if dx == 0 and dy == 0:
            self.point(x0, y0, char)
        elif abs(dx) >= abs(dy):
            for x in range(x0, x1 + 1):
                if dx == 0:
                    y = y0
                else:
                    y = y0 + int(round((x - x0) * dy / float((dx))))
                self.point(x, y, char)
        elif y0 < y1:
            for y in range(y0, y1 + 1):
                if dy == 0:
                    x = x0
                else:
                    x = x0 + int(round((y - y0) * dx / float((dy))))
                self.point(x, y, char)
        else:
            for y in range(y1, y0 + 1):
                if dy == 0:
                    x = x0
                else:
                    x = x1 + int(round((y - y1) * dx / float((dy))))
                self.point(x, y, char)

    def text(self, x, y, text):
        """Print a text on ASCII canvas.

        Args:
            x (int): x coordinate where the text should start.
            y (int): y coordinate where the text should start.
            text (str): string that should be printed.
        """
        for i, char in enumerate(text):
            self.point(x + i, y, char)

    def box(self, x0, y0, width, height):
        """Create a box on ASCII canvas.

        Args:
            x0 (int): x coordinate of the box corner.
            y0 (int): y coordinate of the box corner.
            width (int): box width.
            height (int): box height.
        """
        assert width > 1
        assert height > 1

        width -= 1
        height -= 1

        for x in range(x0, x0 + width):
            self.point(x, y0, "-")
            self.point(x, y0 + height, "-")

        for y in range(y0, y0 + height):
            self.point(x0, y, "|")
            self.point(x0 + width, y, "|")

        self.point(x0, y0, "+")
        self.point(x0 + width, y0, "+")
        self.point(x0, y0 + height, "+")
        self.point(x0 + width, y0 + height, "+")


def _build_sugiyama_layout(vertexes, edges):
    #
    # Just a reminder about naming conventions:
    # +------------X
    # |
    # |
    # |
    # |
    # Y
    #

    vertexes = {v: Vertex(" {} ".format(v)) for v in vertexes}
    # NOTE: reverting edges to correctly orientate the graph
    edges = [Edge(vertexes[e], vertexes[s]) for s, e in edges]
    vertexes = vertexes.values()
    graph = Graph(vertexes, edges)

    for vertex in vertexes:
        vertex.view = VertexViewer(vertex.data)

    # NOTE: determine min box length to create the best layout
    minw = min([v.view.w for v in vertexes])

    for edge in edges:
        edge.view = EdgeViewer()

    sug = SugiyamaLayout(graph.C[0])
    graph = graph.C[0]
    roots = list(filter(lambda x: len(x.e_in()) == 0, graph.sV))

    sug.init_all(roots=roots, optimize=True)

    sug.yspace = VertexViewer.HEIGHT
    sug.xspace = minw
    sug.route_edge = route_with_lines

    sug.draw()

    return sug


def draw(vertexes, edges):
    """Build a DAG and draw it in ASCII.

    Args:
        vertexes (list): list of graph vertexes.
        edges (list): list of graph edges.
    """
    # pylint: disable=too-many-locals
    # NOTE: coordinates might me negative, so we need to shift
    # everything to the positive plane before we actually draw it.
    Xs = []  # pylint: disable=invalid-name
    Ys = []  # pylint: disable=invalid-name

    sug = _build_sugiyama_layout(vertexes, edges)

    for vertex in sug.g.sV:
        # NOTE: moving boxes w/2 to the left
        Xs.append(vertex.view.xy[0] - vertex.view.w / 2.0)
        Xs.append(vertex.view.xy[0] + vertex.view.w / 2.0)
        Ys.append(vertex.view.xy[1])
        Ys.append(vertex.view.xy[1] + vertex.view.h)

    for edge in sug.g.sE:
        for x, y in edge.view._pts:  # pylint: disable=protected-access
            Xs.append(x)
            Ys.append(y)

    minx = min(Xs)
    miny = min(Ys)
    maxx = max(Xs)
    maxy = max(Ys)

    canvas_cols = int(math.ceil(math.ceil(maxx) - math.floor(minx))) + 1
    canvas_lines = int(round(maxy - miny))

    canvas = AsciiCanvas(canvas_cols, canvas_lines)

    # NOTE: first draw edges so that node boxes could overwrite them
    for edge in sug.g.sE:
        # pylint: disable=protected-access
        assert len(edge.view._pts) > 1
        for index in range(1, len(edge.view._pts)):
            start = edge.view._pts[index - 1]
            end = edge.view._pts[index]

            start_x = int(round(start[0] - minx))
            start_y = int(round(start[1] - miny))
            end_x = int(round(end[0] - minx))
            end_y = int(round(end[1] - miny))

            assert start_x >= 0
            assert start_y >= 0
            assert end_x >= 0
            assert end_y >= 0

            canvas.line(start_x, start_y, end_x, end_y, "*")

    for vertex in sug.g.sV:
        # NOTE: moving boxes w/2 to the left
        x = vertex.view.xy[0] - vertex.view.w / 2.0
        y = vertex.view.xy[1]

        canvas.box(
            int(round(x - minx)),
            int(round(y - miny)),
            vertex.view.w,
            vertex.view.h,
        )

        canvas.text(
            int(round(x - minx)) + 1, int(round(y - miny)) + 1, vertex.data
        )

    canvas.draw()
