from dataclasses import dataclass
from abc import ABC, abstractmethod
from typing import Generator

import pygame as pg
from math import pi

from transform import Transform

@dataclass
class Face:
    begin: pg.Vector2
    end: pg.Vector2

    @property
    def normal(self) -> pg.Vector2:
        return (self.end-self.begin).rotate(-90).normalize()
    
@dataclass
class ColliderContact:
    __slots__ = ["points", "normal", "penetration"]
    points: list[pg.Vector2]
    normal: pg.Vector2
    penetration: float

@dataclass(frozen=True)
class PolygonalHull:
    _vertices: list[pg.Vector2]

    def get_vertex_at_index(self, key: int) -> pg.Vector2:
        return self._vertices[key]

    def get_face_at_index(self, key: int) -> Face:
        return Face(self._vertices[key], self._vertices[(key + 1) % len(self._vertices)])
    
    def vertices(self) -> Generator[pg.Vector2, None, None]:
        for v in self._vertices:
            yield v
    
    def faces(self) -> Generator[Face, None, None]:
        for i in range(len(self._vertices)):
            yield self.get_face_at_index(i)

    def project(self, axis: pg.Vector2) -> tuple[float, float]:
        projections = [v.dot(axis) for v in self._vertices]
        return (min(projections), max(projections))


class BaseCollider(ABC):

    @abstractmethod
    def moment_of_inertia(self, mass: float) -> float:
        pass

class ConvexCollider(BaseCollider):

    @abstractmethod
    def hull(self, transform: Transform) -> PolygonalHull:
        pass
    
@dataclass
class CircleCollider(BaseCollider):

    radius: float

    def moment_of_inertia(self, mass: float) -> float:
        return 0.5 * self.radius ** 2 * mass

@dataclass
class LineCollider(ConvexCollider):

    length: float

    def hull(self, transform: Transform) -> PolygonalHull:
        return PolygonalHull([
            transform.global_position - pg.Vector2(self.length / 2.0, 0).rotate(transform.global_degrees) * transform.global_scale,
            transform.global_position + pg.Vector2(self.length / 2.0, 0).rotate(transform.global_degrees) * transform.global_scale
        ])
    
    def moment_of_inertia(self, mass):
        return 1.0 / 12.0 * mass * self.length**2


@dataclass
class RectCollider(ConvexCollider):

    dimensions: tuple[float, float]

    @property
    def width(self):
        return self.dimensions[0]
    
    @property
    def height(self):
        return self.dimensions[1]

    def hull(self, transform: Transform) -> PolygonalHull:
        return PolygonalHull([
            transform.global_position - pg.Vector2(self.width / 2.0, self.height / 2.0).rotate(transform.global_degrees) * transform.global_scale,
            transform.global_position - pg.Vector2(-self.width / 2.0, self.height / 2.0).rotate(transform.global_degrees) * transform.global_scale,
            transform.global_position - pg.Vector2(-self.width / 2.0, -self.height / 2.0).rotate(transform.global_degrees) * transform.global_scale,
            transform.global_position - pg.Vector2(self.width / 2.0, -self.height / 2.0).rotate(transform.global_degrees) * transform.global_scale
        ])

    def moment_of_inertia(self, mass: float) -> float:
        return (1.0 / 12.0) * mass * (self.width ** 2 + self.height ** 2) 

def _interval_overlap(a: tuple[float, float], b: tuple[float, float]) -> float | None:
    if a[0] <= b[1] and b[0] <= a[1]:
        return min(a[1], b[1]) - max(a[0], b[0]) 
    return None

def _collide_circle_circle(a: CircleCollider, b: CircleCollider, a_transform: Transform, b_transform: Transform) -> ColliderContact | None:
    delta = a_transform.global_position - b_transform.global_position
    dist = delta.length()
    radii = b.radius + b.radius
    if dist >= radii or dist == 0:
        return None
    normal = delta.normalize()
    return ColliderContact(
        point=a_transform.global_position + normal * b.radius,
        normal=normal,
        penetration=radii - dist,
        )

def _collide_convex_circle(a: ConvexCollider, b: CircleCollider, a_transform: Transform, b_transform: Transform) -> ColliderContact | None:
    hull = a.hull(a_transform)
    normals = [face.normal for face in hull.faces()]
    circle_normal = min([(b_transform.global_position - v) for v in hull.vertices()], key=lambda v: v.length()).normalize()
    normals.append(circle_normal)
    collision_normal: pg.Vector2 | None = None
    lowest_pen = float('inf')
    for normal in normals:
        center_proj = normal.dot(b_transform.global_position)
        circle_interval = (center_proj - b.radius, center_proj + b.radius)
        convex_interval = hull.project(normal)
        penetration = _interval_overlap(circle_interval, convex_interval)
        if penetration is None:
            return None
        if penetration < lowest_pen:
            lowest_pen = penetration
            collision_normal = normal
    return ColliderContact(
        points=[b_transform.global_position - b.radius*normal],
        normal=collision_normal,
        penetration=lowest_pen
    )

def _collide_convex_convex(a: ConvexCollider, b: ConvexCollider, a_transform: Transform, b_transform: Transform) -> ColliderContact | None:  
    #SAT
    hull_a = a.hull(a_transform)
    hull_b = b.hull(b_transform)
    normals = [*[face.normal for face in hull_a.faces()],*[face.normal for face in hull_b.faces()]]
    collision_normal: pg.Vector2 | None = None
    lowest_pen = float('inf')
    for normal in normals:
        a_interval = hull_a.project(normal)
        b_interval = hull_b.project(normal)
        penetration = _interval_overlap(a_interval, b_interval)
        if penetration is None:
            return None
        if penetration < lowest_pen and (a_transform.position - b_transform.position).dot(normal) > 0:
            lowest_pen = penetration
            collision_normal = normal


    #sutherland hodgman clipping
    ref_face = max(hull_b.faces(), key=lambda f: f.normal.dot(collision_normal))
    incident_face = min(hull_a.faces(), key=lambda f: f.normal.dot(collision_normal))
    left_normal = (ref_face.begin - ref_face.end).normalize()
    right_normal = (ref_face.end - ref_face.begin).normalize()

    contact_manifold = [incident_face.begin, incident_face.end]

    def clip(normal: pg.Vector2, ref_point: pg.Vector2) -> None:
        d1 = (contact_manifold[0] - ref_point).dot(normal)
        d2 = (contact_manifold[1] - ref_point).dot(normal)
        if d1 > 0 and d2 > 0:
            raise Exception("CLIPPING ERROR")
        if d1 > 0:
            contact_manifold[0] = contact_manifold[0] + (d1 / (d1 - d2)) * (contact_manifold[1] - contact_manifold[0])
        if d2 > 0:
            contact_manifold[1] = contact_manifold[1] + (d2 / (d2 - d1)) * (contact_manifold[0] - contact_manifold[1])

    clip(right_normal, ref_face.end)
    clip(left_normal, ref_face.begin)
    clip(ref_face.normal, ref_face.begin)

    return ColliderContact(
        points=contact_manifold,
        normal=collision_normal,
        penetration=lowest_pen
    )

def intersect(a: BaseCollider, b: BaseCollider, a_transform: Transform, b_transform: Transform) -> ColliderContact | None:
    if isinstance(a, ConvexCollider) and isinstance(b, ConvexCollider):
        return _collide_convex_convex(a,b,a_transform,b_transform)
    if isinstance(a, ConvexCollider) and isinstance(b, CircleCollider):
        return _collide_convex_circle(a, b, a_transform, b_transform)
    if isinstance(a, CircleCollider) and isinstance(b, ConvexCollider):
        collision = _collide_convex_circle(b,a,b_transform,a_transform)
        if collision: collision.normal *= -1
        return collision
    if isinstance(a, CircleCollider) and isinstance(b, CircleCollider):
        return _collide_circle_circle(a,b,a_transform,b_transform)
    raise NotImplementedError(f"No collision defined between collider types {type(a)} and {type(b)}")