"""Depth aware 3D drawing canvas."""

from __future__ import annotations

from dataclasses import dataclass, field
from datetime import datetime
from pathlib import Path

import cv2
import numpy as np

from canvas import PALETTE
from smoothing import OneEuroFilter

MAX_JUMP = 0.12
MIN_STEP = 2.0
DEPTH_SPAN = 1.15
DEPTH_PX_PER_METER = 1.7
DEPTH_MIN_METERS = 0.12
DEPTH_BAND = 0.015
DEPTH_MAX_SPEED = 1.1
DEPTH_CUTOFF = 0.8
DEPTH_BETA = 4.0
DEPTH_STEP = 5.0
GRADIENT_SPAN = 0.5
GRADIENT_LO = 40
GRADIENT_HI = 218
TAIL = 7
NEAR_GAIN = 1.35
FAR_GAIN = 0.55
GRADIENT_NEAR_GAIN = 1.12
GRADIENT_FAR_GAIN = 0.80

_TURBO: np.ndarray = cv2.applyColorMap(
    np.arange(256, dtype=np.uint8).reshape(-1, 1), cv2.COLORMAP_TURBO
).reshape(-1, 3)


@dataclass
class View:
    """Camera orientation and zoom."""

    yaw: float = 0.0
    pitch: float = 0.0
    roll: float = 0.0
    scale: float = 1.0


@dataclass
class Stroke3D:
    """One stroke in world space."""

    color: tuple[int, int, int]
    thickness: int
    gradient: bool = False
    view: View = field(default_factory=View)
    points: list[tuple[float, float, float]] = field(default_factory=list)
    screen: list[tuple[float, float]] = field(default_factory=list)


class DepthPen:
    """Noise tolerant metric depth."""

    def __init__(self, band: float = DEPTH_BAND, max_speed: float = DEPTH_MAX_SPEED) -> None:
        self.band = band
        self.max_speed = max_speed
        self.filter = OneEuroFilter(min_cutoff=DEPTH_CUTOFF, beta=DEPTH_BETA)
        self.value: float | None = None
        self.raw: float = 0.0

    def reset(self) -> None:
        """Drop tracking state."""
        self.filter.reset()
        self.value = None

    def __call__(self, depth_meters: float, dt: float) -> float | None:
        """Filter one depth sample."""
        d = float(depth_meters)
        if not np.isfinite(d) or d < DEPTH_MIN_METERS:
            return self.value
        step = max(float(dt), 1e-3)
        self.raw = d
        smooth = float(self.filter(np.array([d], dtype=np.float64), step)[0])
        if self.value is None:
            self.value = smooth
            return self.value
        delta = smooth - self.value
        if abs(delta) <= self.band:
            return self.value
        move = np.sign(delta) * (abs(delta) - self.band)
        limit = self.max_speed * step
        self.value += float(np.clip(move, -limit, limit))
        return self.value


def rotation(yaw: float, pitch: float, roll: float) -> np.ndarray:
    """Build rotation matrix."""
    cy, sy = np.cos(yaw), np.sin(yaw)
    cp, sp = np.cos(pitch), np.sin(pitch)
    cr, sr = np.cos(roll), np.sin(roll)
    ry = np.array([[cy, 0.0, sy], [0.0, 1.0, 0.0], [-sy, 0.0, cy]])
    rx = np.array([[1.0, 0.0, 0.0], [0.0, cp, -sp], [0.0, sp, cp]])
    rz = np.array([[cr, -sr, 0.0], [sr, cr, 0.0], [0.0, 0.0, 1.0]])
    return rz @ ry @ rx


class Canvas3D:
    """Vector canvas with per point depth."""

    def __init__(self, width: int, height: int, output_dir: str | Path = "output") -> None:
        self.width = width
        self.height = height
        self.output_dir = Path(output_dir)
        self.strokes: list[Stroke3D] = []
        self._active: Stroke3D | None = None
        self.color: tuple[int, int, int] = PALETTE[0]
        self.gradient = True
        self.thickness: int = 6
        self.revision = 0
        self.depth_span = float(height) * DEPTH_SPAN
        self.gradient_span = float(height) * GRADIENT_SPAN
        self.distance = float(height) * 2.2
        self.focal = self.distance
        self.px_per_meter = float(height) * DEPTH_PX_PER_METER
        self.depth_ref: float | None = None
        self.last_depth: float = 0.0
        self.last_z: float = 0.0
        self.view = View()
        self.pen = DepthPen()
        self._last_screen: tuple[float, float] | None = None
        self._last_z = 0.0

    def set_view(self, view: View) -> None:
        """Store the current camera."""
        self.view = view

    def depth_to_world_z(self, depth_meters: float, dt: float) -> float:
        """Map metric depth to world Z."""
        held = self.pen(depth_meters, dt)
        if held is None:
            return self.last_z
        if self.depth_ref is None:
            self.depth_ref = held
        self.last_depth = held
        self.last_z = float(np.clip((held - self.depth_ref) * self.px_per_meter,
                                    -self.depth_span, self.depth_span))
        return self.last_z

    def depth_color(self, world_z: float) -> tuple[int, int, int]:
        """Gradient color for a depth."""
        t = float(np.clip((world_z + self.gradient_span) / (2.0 * self.gradient_span), 0.0, 1.0))
        b, g, r = _TURBO[int(round(GRADIENT_LO + (1.0 - t) * (GRADIENT_HI - GRADIENT_LO)))]
        return int(b), int(g), int(r)

    def pen_color(self) -> tuple[int, int, int]:
        """Color the pen draws with now."""
        return self.depth_color(self.last_z) if self.gradient else self.color

    def use_gradient(self) -> None:
        """Color strokes by depth."""
        self.gradient = True

    def _matrix(self, view: View | None = None) -> np.ndarray:
        """Scaled rotation matrix."""
        v = view or self.view
        return rotation(v.yaw, v.pitch, v.roll) * max(v.scale, 1e-3)

    def project(self, points: np.ndarray, view: View | None = None) -> tuple[np.ndarray, np.ndarray]:
        """Project world points to screen."""
        pts = np.asarray(points, dtype=np.float64).reshape(-1, 3)
        cam = pts @ self._matrix(view).T
        z = np.maximum(cam[:, 2] + self.distance, 1e-3)
        cx, cy = self.width * 0.5, self.height * 0.5
        sx = cx + self.focal * cam[:, 0] / z
        sy = cy + self.focal * cam[:, 1] / z
        return np.stack([sx, sy], axis=1), z

    def unproject(self, screen: np.ndarray, world_z: float,
                  view: View | None = None) -> tuple[float, float, float]:
        """Screen point at known depth to world."""
        a = self._matrix(view)
        cx, cy = self.width * 0.5, self.height * 0.5
        u = float(screen[0]) - cx
        v = float(screen[1]) - cy
        f = self.focal
        m = np.array(
            [
                [f * a[0, 0] - u * a[2, 0], f * a[0, 1] - u * a[2, 1]],
                [f * a[1, 0] - v * a[2, 0], f * a[1, 1] - v * a[2, 1]],
            ],
            dtype=np.float64,
        )
        rhs = np.array(
            [
                u * (a[2, 2] * world_z + self.distance) - f * a[0, 2] * world_z,
                v * (a[2, 2] * world_z + self.distance) - f * a[1, 2] * world_z,
            ],
            dtype=np.float64,
        )
        det = m[0, 0] * m[1, 1] - m[0, 1] * m[1, 0]
        if abs(det) < 1e-9:
            return 0.0, 0.0, world_z
        x, y = np.linalg.solve(m, rhs)
        return float(x), float(y), float(world_z)

    def begin(self, view: View | None = None) -> None:
        """Start a new stroke."""
        if self._active is None:
            self._active = Stroke3D(color=self.color, thickness=self.thickness,
                                    gradient=self.gradient, view=view or self.view)
            self.strokes.append(self._active)
            self._last_screen = None

    def add_point(self, screen_point, depth_meters: float, dt: float,
                  view: View | None = None) -> None:
        """Append a screen point with metric depth."""
        if self._active is None:
            self.begin(view)
        assert self._active is not None
        sx = float(np.clip(float(screen_point[0]), 0.0, self.width - 1.0))
        sy = float(np.clip(float(screen_point[1]), 0.0, self.height - 1.0))
        z = self.depth_to_world_z(depth_meters, dt)

        if self._last_screen is not None:
            jump = float(np.hypot(sx - self._last_screen[0], sy - self._last_screen[1]))
            if jump < MIN_STEP and abs(z - self._last_z) < DEPTH_STEP:
                return
            if jump > MAX_JUMP * float(np.hypot(self.width, self.height)):
                self.end()
                self.begin(view)
                assert self._active is not None

        stroke = self._active
        stroke.points.append(self.unproject(np.array([sx, sy]), z, stroke.view))
        stroke.screen.append((sx, sy))
        self._smooth_tail()
        self._last_screen = (sx, sy)
        self._last_z = z
        self.revision += 1

    def _smooth_tail(self) -> None:
        """Low pass the newest depths."""
        stroke = self._active
        if stroke is None or len(stroke.points) < 3:
            return
        n = len(stroke.points)
        zs = [p[2] for p in stroke.points]
        for i in range(max(1, n - TAIL), n - 1):
            z = 0.25 * zs[i - 1] + 0.5 * zs[i] + 0.25 * zs[i + 1]
            if abs(z - zs[i]) < 1e-3:
                continue
            stroke.points[i] = self.unproject(np.array(stroke.screen[i]), z, stroke.view)

    def end(self) -> None:
        """Finish current stroke."""
        if self._active is not None and not self._active.points:
            self.strokes.remove(self._active)
            self.revision += 1
        self._active = None
        self._last_screen = None
        self.pen.reset()

    def undo(self) -> None:
        """Remove last stroke."""
        if self.strokes:
            self.strokes.pop()
            self._active = None
            self._last_screen = None
            self.revision += 1

    def clear(self) -> None:
        """Erase everything."""
        self.strokes.clear()
        self._active = None
        self._last_screen = None
        self._last_z = 0.0
        self.pen.reset()
        self.depth_ref = None
        self.revision += 1

    def set_color(self, index: int) -> None:
        """Select palette color."""
        self.color = PALETTE[index % len(PALETTE)]
        self.gradient = False

    def set_thickness(self, value: int) -> None:
        """Set stroke thickness."""
        self.thickness = int(max(1, min(48, value)))

    def scale_content(self, factor: float) -> None:
        """Scale drawing about origin."""
        if not self.strokes or abs(factor - 1.0) < 1e-3:
            return
        for s in self.strokes:
            s.points = [(x * factor, y * factor, z * factor) for x, y, z in s.points]
            s.thickness = int(max(1, min(48, round(s.thickness * factor))))
        self._active = None
        self._last_screen = None
        self.revision += 1

    @property
    def is_empty(self) -> bool:
        """No strokes drawn."""
        return not any(s.points for s in self.strokes)

    def all_points(self) -> np.ndarray:
        """Every world point."""
        pts = [p for s in self.strokes for p in s.points]
        if not pts:
            return np.zeros((0, 3), dtype=np.float64)
        return np.asarray(pts, dtype=np.float64)

    def content_span(self, view: View | None = None) -> float:
        """Projected diagonal length."""
        pts = self.all_points()
        if pts.shape[0] == 0:
            return 0.0
        proj, _ = self.project(pts, view)
        x0, y0 = proj.min(axis=0)
        x1, y1 = proj.max(axis=0)
        return float(np.hypot(x1 - x0, y1 - y0))

    def _segments(self, view: View | None = None) -> list[tuple[float, np.ndarray, np.ndarray, tuple[int, int, int], int]]:
        """Depth sorted screen segments."""
        out: list[tuple[float, np.ndarray, np.ndarray, tuple[int, int, int], int]] = []
        for s in self.strokes:
            if not s.points:
                continue
            pts = np.asarray(s.points, dtype=np.float64)
            proj, z = self.project(pts, view)
            if len(s.points) == 1:
                color = self.depth_color(pts[0, 2]) if s.gradient else s.color
                out.append((float(z[0]), proj[0], proj[0],
                            self._shade(color, float(z[0]), s.gradient), s.thickness))
                continue
            for i in range(len(s.points) - 1):
                zc = float((z[i] + z[i + 1]) * 0.5)
                if s.gradient:
                    color = self.depth_color(float((pts[i, 2] + pts[i + 1, 2]) * 0.5))
                else:
                    color = s.color
                out.append((zc, proj[i], proj[i + 1],
                            self._shade(color, zc, s.gradient), s.thickness))
        out.sort(key=lambda item: item[0], reverse=True)
        return out

    def _shade(self, color: tuple[int, int, int], z: float,
               gradient: bool = False) -> tuple[int, int, int]:
        """Dim color by distance."""
        t = float(np.clip((z - self.distance) / max(self.depth_span, 1e-6) + 0.5, 0.0, 1.0))
        near, far = (GRADIENT_NEAR_GAIN, GRADIENT_FAR_GAIN) if gradient else (NEAR_GAIN, FAR_GAIN)
        gain = near + (far - near) * t
        return tuple(int(np.clip(c * gain, 0, 255)) for c in color)

    def _thickness_at(self, base: int, z: float) -> int:
        """Perspective scaled thickness."""
        k = self.focal / max(z, 1e-3)
        return int(max(1, min(64, round(base * k))))

    def render_over(self, frame: np.ndarray, view: View | None = None) -> np.ndarray:
        """Draw strokes onto a frame."""
        out = frame.copy()
        for z, a, b, color, thick in self._segments(view):
            pa = (int(round(a[0])), int(round(a[1])))
            pb = (int(round(b[0])), int(round(b[1])))
            width = self._thickness_at(thick, z)
            if pa == pb:
                cv2.circle(out, pa, max(1, width // 2), color, -1, cv2.LINE_AA)
            else:
                cv2.line(out, pa, pb, color, width, cv2.LINE_AA)
        return out

    def composite_over(self, frame: np.ndarray, opacity: float = 1.0) -> np.ndarray:
        """Blend drawing onto frame."""
        drawn = self.render_over(frame, self.view)
        if opacity >= 1.0:
            return drawn
        return cv2.addWeighted(drawn, opacity, frame, 1.0 - opacity, 0.0)

    def layers(self, view: View | None = None) -> tuple[np.ndarray, np.ndarray]:
        """Color layer and alpha mask."""
        layer = np.zeros((self.height, self.width, 3), dtype=np.uint8)
        mask = np.zeros((self.height, self.width), dtype=np.uint8)
        for z, a, b, color, thick in self._segments(view):
            pa = (int(round(a[0])), int(round(a[1])))
            pb = (int(round(b[0])), int(round(b[1])))
            width = self._thickness_at(thick, z)
            if pa == pb:
                cv2.circle(layer, pa, max(1, width // 2), color, -1, cv2.LINE_AA)
                cv2.circle(mask, pa, max(1, width // 2), 255, -1, cv2.LINE_AA)
            else:
                cv2.line(layer, pa, pb, color, width, cv2.LINE_AA)
                cv2.line(mask, pa, pb, 255, width, cv2.LINE_AA)
        return layer, mask

    def to_bgra(self, view: View | None = None) -> np.ndarray:
        """Drawing with transparent background."""
        layer, mask = self.layers(view)
        return np.dstack([layer, mask])

    def save(self, tag: str = "3d") -> list[Path]:
        """Save current view as PNGs."""
        self.output_dir.mkdir(parents=True, exist_ok=True)
        stamp = datetime.now().strftime("%Y%m%d_%H%M%S")
        suffix = f"_{tag}" if tag else ""
        saved: list[Path] = []

        layer, mask = self.layers(self.view)
        transparent = self.output_dir / f"drawing_{stamp}{suffix}.png"
        cv2.imwrite(str(transparent), np.dstack([layer, mask]))
        saved.append(transparent)

        white = np.full((self.height, self.width, 3), 255, dtype=np.uint8)
        alpha = (mask.astype(np.float32) / 255.0)[:, :, None]
        flat = (white * (1.0 - alpha) + layer * alpha).astype(np.uint8)
        on_white = self.output_dir / f"drawing_{stamp}{suffix}_white.png"
        cv2.imwrite(str(on_white), flat)
        saved.append(on_white)

        return saved