from __future__ import annotations

from collections.abc import Sequence

import torch
import torch.nn.functional as F

Point = Sequence[float]  # (x, y) or (x, y, theta_degrees)

RS = "\x1e"

# Pattern-class vocabulary (EFS 9.307): whorl / loops / arches / unclassifiable.
# Mapped to a fixed index for global one-hot conditioning. Sub-codes (e.g. "LS",
# "RS", "WU", "AU", "TA", "PA") collapse to their family by first letter group.
PATTERN_CLASSES = ["whorl", "loop", "arch", "other"]


def pattern_to_index(code: str) -> int:
    """Map an EFS 9.307 pattern code to a PATTERN_CLASSES index (whorl/loop/arch/other)."""
    c = (code or "").strip().upper().split("\x1f")[0].split("\x1e")[0][:2]
    if c.startswith("W"):
        return 0  # whorl (WU, etc.)
    if c in ("LS", "RS") or c.startswith("L") or c.startswith("R"):
        return 1  # loop (left/right slant)
    if c.startswith("A") or c in ("TA", "PA"):
        return 2  # arch (tented/plain)
    return 3  # UC / unclassifiable / other


def pattern_onehot(code: str) -> list[float]:
    v = [0.0] * len(PATTERN_CLASSES)
    v[pattern_to_index(code)] = 1.0
    return v


def compute_orientation_field(
    image: torch.Tensor, block: int = 8, sigma_smooth: int = 9
) -> torch.Tensor:
    """Ridge orientation field via the gradient structure tensor.

    Returns ``(B, 2, H, W)`` = ``[cos(2θ), sin(2θ)] * coherence``. Using the
    double-angle (2θ) encoding avoids the orientation wrap-around at 0/π, and
    weighting by coherence down-weights noisy/blank regions (low coherence → ~0),
    so it is a clean dense conditioning/loss signal that is registered to the image
    (computed from the image itself, no annotation needed). Identity-bearing: it
    captures ridge flow, the basis of pattern class and singular points.
    """
    if image.ndim != 4:
        raise ValueError(f"expected (B,C,H,W), got {tuple(image.shape)}")
    g = image if image.shape[1] == 1 else image.mean(1, keepdim=True)
    kx = torch.tensor([[-1, 0, 1], [-2, 0, 2], [-1, 0, 1]], dtype=g.dtype, device=g.device).view(1, 1, 3, 3)
    ky = kx.transpose(-1, -2)
    # Replicate-pad before Sobel: zero padding fabricates strong gradients along
    # the image border (a flat/blank image otherwise gets a high-coherence ring,
    # which leaks through the foreground gate and pollutes orientation losses).
    g = F.pad(g, (1, 1, 1, 1), mode="replicate")
    gx = F.conv2d(g, kx)
    gy = F.conv2d(g, ky)
    gxx, gyy, gxy = gx * gx, gy * gy, gx * gy
    pad = sigma_smooth // 2
    sm = lambda t: F.avg_pool2d(t, sigma_smooth, stride=1, padding=pad)
    gxx, gyy, gxy = sm(gxx), sm(gyy), sm(gxy)
    cos2 = gxx - gyy
    sin2 = 2 * gxy
    # Epsilon INSIDE the sqrt: d/dx sqrt(x) -> inf at x=0, so sqrt(0)+eps still
    # backprops NaN on exactly-flat regions. This function runs on generator
    # OUTPUTS (regen orientation loss, equalized critic cond), and the foreground
    # gate makes outputs exactly equal flat inputs there — sqrt(0) killed a full
    # training run (every weight NaN within epoch 0) before this guard.
    mag = torch.sqrt(cos2 * cos2 + sin2 * sin2 + 1e-12) + 1e-6
    coh = mag / (gxx + gyy + 1e-6)  # coherence in [0,1]
    return torch.cat([cos2 / mag * coh, sin2 / mag * coh], dim=1)


def parse_quality_grid(value: str) -> list[list[int]]:
    """Parse a Type-9 ``9.308`` ridge-quality grid (RS-separated digit rows).

    Returns a rectangular int grid (rows of equal length); ragged input is
    right-padded with zeros. Values are quality levels (0=background .. 5).
    """
    rows = [row for row in value.split(RS) if row]
    grid = [[int(c) for c in row if c.isdigit()] for row in rows]
    grid = [r for r in grid if r]
    if not grid:
        return []
    width = max(len(r) for r in grid)
    return [r + [0] * (width - len(r)) for r in grid]


def render_quality_grid(
    grid: str | list[list[int]],
    out_size: int,
    max_level: int = 5,
    binarize: bool = False,
    device: torch.device | str = "cpu",
    dtype: torch.dtype = torch.float32,
) -> torch.Tensor:
    """Render a ``9.308`` quality grid as a dense ``(1, out, out)`` channel.

    The grid spans the full annotation image frame, so it is spatially registered
    to the (uniformly-scaled) latent image and is upsampled to ``out_size``. With
    ``binarize=True`` it returns a foreground mask (level>0), suitable as the
    ``M_fg`` for ``L_seg``; otherwise quality is normalised to ``[0,1]``.
    Empty grid -> all-ones (no annotation = treat everything as valid, the safe
    default for a mask) when binarized, else zeros.
    """
    if isinstance(grid, str):
        grid = parse_quality_grid(grid)
    if not grid:
        fill = 1.0 if binarize else 0.0
        return torch.full((1, out_size, out_size), fill, device=device, dtype=dtype)
    t = torch.tensor(grid, device=device, dtype=dtype).unsqueeze(0).unsqueeze(0)
    if binarize:
        t = (t > 0).to(dtype)
    else:
        t = t.clamp(0, max_level) / float(max_level)
    # pad_square-aware (match resize_pad_square): the grid spans the frame, so its aspect
    # = frame aspect -> uniform-resize the longer side then center-pad, NOT anisotropic
    # stretch (which misregistered the quality/ROI mask vs the padded latent image).
    hg, wg = t.shape[-2], t.shape[-1]
    s = out_size / max(hg, wg)
    nh, nw = max(1, round(hg * s)), max(1, round(wg * s))
    t = F.interpolate(t, size=(nh, nw), mode="bilinear", align_corners=False)
    canvas = torch.zeros(1, 1, out_size, out_size, device=device, dtype=dtype)
    oy, ox = (out_size - nh) // 2, (out_size - nw) // 2
    canvas[:, :, oy:oy + nh, ox:ox + nw] = t
    return canvas[0]


def structural_channel_names(orientation: bool = False) -> list[str]:
    """Channel order produced by :func:`build_structural_conditioning`."""
    names = ["minutiae", "core", "delta"]
    if orientation:
        names += ["minutiae_sin", "minutiae_cos"]
    return names


def render_gaussian_points(
    points: Sequence[Point],
    out_size: int,
    src_size: tuple[float, float] | None = None,
    sigma: float = 3.0,
    weights: Sequence[float] | None = None,
    device: torch.device | str = "cpu",
    dtype: torch.dtype = torch.float32,
) -> torch.Tensor:
    """Render points as a single-channel Gaussian heatmap ``(1, out, out)``.

    Coordinates are in the pixel system of the source annotation image. Pass
    ``src_size=(W, H)`` (the EFS record's image size, e.g. 9.300) to rescale onto
    the ``out_size`` training grid; omit it if points are already in ``out_size``
    pixels. Peaks are 1.0 at each point (or ``weights[i]`` if given). An empty
    point list yields an all-zero map, which is the correct conditioning for a
    latent that genuinely has no annotated core/delta.
    """
    hm = torch.zeros(1, out_size, out_size, device=device, dtype=dtype)
    if not points:
        return hm

    # pad_square-aware mapping: MATCH FingerprintTransform.resize_pad_square (uniform
    # scale of the longer side + centered pad), NOT an anisotropic stretch. The old
    # anisotropic (out/W, out/H) misregistered minutiae vs the padded image by mean ~8px
    # (up to 38px, 14% of pairs >15px tol) on non-square latents -> the minutiae anchor
    # rewarded ridge energy at the WRONG pixels.
    if src_size:
        s = out_size / max(float(src_size[0]), float(src_size[1]))
        sx = sy = s
        ox = (out_size - float(src_size[0]) * s) / 2.0
        oy = (out_size - float(src_size[1]) * s) / 2.0
    else:
        sx = sy = 1.0
        ox = oy = 0.0

    yy, xx = torch.meshgrid(
        torch.arange(out_size, device=device, dtype=dtype),
        torch.arange(out_size, device=device, dtype=dtype),
        indexing="ij",
    )
    two_s2 = 2.0 * float(sigma) * float(sigma)
    for i, point in enumerate(points):
        x = float(point[0]) * sx + ox
        y = float(point[1]) * sy + oy
        if not (0 <= x < out_size and 0 <= y < out_size):
            continue
        w = float(weights[i]) if weights is not None else 1.0
        hm[0] += w * torch.exp(-((xx - x) ** 2 + (yy - y) ** 2) / two_s2)
    return hm.clamp(0.0, 1.0)


def conditioning_from_sidecar(
    sidecar: dict,
    out_size: int,
    channels: Sequence[str] = ("quality", "minutiae"),
    prefix: str = "latent",
    sigma_minutiae: float = 3.0,
    sigma_singular: float = 6.0,
    image: torch.Tensor | None = None,
    device: torch.device | str = "cpu",
    dtype: torch.dtype = torch.float32,
) -> torch.Tensor:
    """Build a registered conditioning tensor ``(len(channels), out, out)`` from a
    pair-annotation sidecar (see scripts/extract_pair_annotations.py).

    Channels are registered to the image of the chosen side via its frame:
    ``prefix="latent"`` (default) uses ``latent_frame`` / ``latent_minutiae`` ...;
    ``prefix="mate"`` uses ``mate_frame`` / ``mate_minutiae`` ... so the mate
    conditioning is registered to the *mate* image. ``channels`` may include
    ``"quality"`` (dense 9.308 grid, latent-only -> zeros for mate), ``"minutiae"``,
    ``"core"``, ``"delta"``.
    """
    frame = sidecar.get(f"{prefix}_frame")
    src = (float(frame[0]), float(frame[1])) if frame else None
    kw = dict(out_size=out_size, device=device, dtype=dtype)
    field = {
        "minutiae": f"{prefix}_minutiae",
        "core": f"{prefix}_cores",
        "delta": f"{prefix}_deltas",
    }
    maps = []
    for ch in channels:
        if ch == "quality":
            maps.append(render_quality_grid(sidecar.get(f"{prefix}_quality_grid", ""), **kw))
        elif ch == "orientation":
            # 2-channel dense ridge-flow field, computed from the image itself
            # (registered). Requires `image` (B=1,1,H,W) in [0,1].
            if image is None:
                maps.append(torch.zeros(2, out_size, out_size, device=device, dtype=dtype))
            else:
                of = compute_orientation_field(image.to(device=device, dtype=dtype))
                of = F.interpolate(of, size=(out_size, out_size), mode="bilinear", align_corners=False)
                maps.append(of[0])
        elif ch in field:
            sigma = sigma_minutiae if ch == "minutiae" else sigma_singular
            maps.append(render_gaussian_points(
                sidecar.get(field[ch], []), src_size=src, sigma=sigma, **kw))
        else:
            raise ValueError(f"Unknown conditioning channel: {ch}")
    return torch.cat(maps, dim=0)


def cond_channel_count(channels: Sequence[str]) -> int:
    """Number of tensor channels produced for a channel list (orientation = 2)."""
    return sum(2 if c == "orientation" else 1 for c in channels)


def build_structural_conditioning(
    minutiae: Sequence[Point],
    cores: Sequence[Point],
    deltas: Sequence[Point],
    out_size: int,
    src_size: tuple[float, float] | None = None,
    sigma_minutiae: float = 3.0,
    sigma_singular: float = 6.0,
    orientation: bool = False,
    device: torch.device | str = "cpu",
    dtype: torch.dtype = torch.float32,
) -> torch.Tensor:
    """Stack annotation channels into a conditioning tensor ``(C, out, out)``.

    Base channels: ``[minutiae, core, delta]``. Singular points use a larger
    sigma because they are coarse, low-count topological landmarks. With
    ``orientation=True`` two extra channels encode minutiae direction as
    ``sin``/``cos`` weighted heatmaps (theta in degrees from the 3rd column),
    giving the critic ridge-flow context. Channel order matches
    :func:`structural_channel_names`.
    """
    kw = dict(out_size=out_size, src_size=src_size, device=device, dtype=dtype)
    channels = [
        render_gaussian_points(minutiae, sigma=sigma_minutiae, **kw),
        render_gaussian_points(cores, sigma=sigma_singular, **kw),
        render_gaussian_points(deltas, sigma=sigma_singular, **kw),
    ]
    if orientation:
        import math

        sin_w = [math.sin(math.radians(float(p[2]))) if len(p) > 2 else 0.0 for p in minutiae]
        cos_w = [math.cos(math.radians(float(p[2]))) if len(p) > 2 else 0.0 for p in minutiae]
        channels.append(
            render_gaussian_points(minutiae, sigma=sigma_minutiae, weights=sin_w, **kw)
        )
        channels.append(
            render_gaussian_points(minutiae, sigma=sigma_minutiae, weights=cos_w, **kw)
        )
    return torch.cat(channels, dim=0)