"""Data loading utilities: synthetic generation, built-in datasets, CSV upload."""

from __future__ import annotations

import math
from dataclasses import dataclass
from typing import Literal, Optional, Sequence

import numpy as np
import pandas as pd

PatternType = Literal["constant", "sinusoidal", "step", "stairs", "linear", "mixed", "gp"]

MAX_UPLOAD_POINTS = 200_000  # safety limit for HF Spaces


@dataclass
class TimeSeriesData:
    """Container for a loaded time series with optional ground truth."""

    signal: np.ndarray  # shape (n_timestamps, n_dims)
    ground_truth: Optional[np.ndarray] = None  # state labels, shape (n_timestamps,)
    change_points: Optional[list[int]] = None
    name: str = "Unknown"
    n_dims: int = 1

    def __post_init__(self):
        if self.signal.ndim == 1:
            self.signal = self.signal[:, np.newaxis]
        self.n_dims = self.signal.shape[1]
        if self.ground_truth is not None and self.change_points is None:
            self.change_points = _states_to_cps(self.ground_truth)

    @property
    def length(self) -> int:
        return self.signal.shape[0]

    @property
    def n_states(self) -> int:
        if self.ground_truth is not None:
            return int(self.ground_truth.max()) + 1
        return 0

    @property
    def has_ground_truth(self) -> bool:
        return self.ground_truth is not None


def _states_to_cps(states: np.ndarray) -> list[int]:
    diffs = np.diff(states)
    return list(np.nonzero(diffs)[0] + 1)


# ---------------------------------------------------------------------------
# Synthetic Data
# ---------------------------------------------------------------------------


@dataclass
class SyntheticSeries:
    signal: np.ndarray
    change_points: list[int]
    change_points_one_hot: np.ndarray
    states: np.ndarray


def _generate_boundaries(
    length: int,
    n_segments: int,
    rng: np.random.Generator,
    min_segment_length: int = 20,
) -> list[int]:
    if n_segments < 1:
        raise ValueError("n_segments must be >= 1")
    if length <= n_segments:
        raise ValueError("length must exceed number of segments")
    if min_segment_length * n_segments > length:
        min_segment_length = max(1, length // n_segments)
    proportions = rng.dirichlet(alpha=np.ones(n_segments))
    segment_lengths = np.maximum(min_segment_length, (proportions * length).astype(int))
    # Redistribute excess/deficit so that no segment becomes negative
    delta = length - int(segment_lengths.sum())
    if delta > 0:
        # Distribute extra samples round-robin
        for i in range(delta):
            segment_lengths[i % n_segments] += 1
    elif delta < 0:
        # Remove excess samples from the largest segments first
        for _ in range(-delta):
            idx = int(np.argmax(segment_lengths))
            if segment_lengths[idx] <= min_segment_length:
                # All segments are at minimum; shrink the largest anyway
                idx = int(np.argmax(segment_lengths))
            segment_lengths[idx] -= 1
    boundaries: list[int] = []
    cursor = 0
    for seg_len in segment_lengths[:-1]:
        cursor += int(seg_len)
        boundaries.append(min(cursor, length - 1))
    return [cp for cp in boundaries if cp < length]


def _sine_segment(start, stop, n_dims, mean_offset, amplitude, freq, phase, noise_level, rng):
    t = np.linspace(0, 1, stop - start, endpoint=False)
    base = amplitude * np.sin(2 * math.pi * (freq * t + phase)) + mean_offset
    noise_scale = (0.05 * amplitude if amplitude else 0.05) * noise_level
    noise = rng.normal(scale=max(noise_scale, 1e-12), size=(stop - start, n_dims))
    return np.tile(base[:, None], (1, n_dims)) + noise


def _complex_segment(start, stop, n_dims, trend, curvature, freq, noise_level, rng):
    t = np.linspace(0, 1, stop - start, endpoint=False)
    base = trend * t + curvature * (t - 0.5) ** 2
    seasonal = np.sin(2 * math.pi * freq * t)
    features = base + 0.6 * seasonal
    out = np.empty((stop - start, n_dims))
    for dim in range(n_dims):
        noise = rng.normal(scale=max(0.1 * noise_level, 1e-12), size=features.shape)
        drift = rng.normal(scale=max(0.2 * noise_level, 1e-12)) * t
        out[:, dim] = features + drift + noise
    return out


# -- Pattern-based segment generators --


def _gen_constant(length: int, n_dims: int, level: float, noise_level: float, rng) -> np.ndarray:
    """Flat segment at a given level."""
    noise = rng.normal(scale=max(0.05 * noise_level, 1e-12), size=(length, n_dims))
    return np.full((length, n_dims), level) + noise


def _gen_sinusoidal(
    length: int, n_dims: int, amplitude: float, freq: float, phase: float, offset: float, noise_level: float, rng
) -> np.ndarray:
    """Sinusoidal segment."""
    t = np.linspace(0, 1, length, endpoint=False)
    base = amplitude * np.sin(2 * math.pi * (freq * t + phase)) + offset
    noise = rng.normal(scale=max(0.05 * amplitude * noise_level, 1e-12), size=(length, n_dims))
    return np.tile(base[:, None], (1, n_dims)) + noise


def _gen_step(length: int, n_dims: int, levels: Sequence[float], noise_level: float, rng) -> np.ndarray:
    """Piecewise-constant (step function) within a single segment."""
    n_steps = len(levels)
    step_len = length // n_steps
    out = np.empty((length, n_dims))
    for i, lvl in enumerate(levels):
        start = i * step_len
        stop = (i + 1) * step_len if i < n_steps - 1 else length
        out[start:stop] = lvl
    noise = rng.normal(scale=max(0.05 * noise_level, 1e-12), size=(length, n_dims))
    return out + noise


def _gen_stairs(
    length: int, n_dims: int, start_level: float, step_size: float, n_stairs: int, noise_level: float, rng
) -> np.ndarray:
    """Staircase pattern — monotonically increasing within the segment."""
    stair_len = length // max(n_stairs, 1)
    out = np.empty((length, n_dims))
    for i in range(n_stairs):
        s = i * stair_len
        e = (i + 1) * stair_len if i < n_stairs - 1 else length
        out[s:e] = start_level + i * step_size
    noise = rng.normal(scale=max(0.05 * noise_level, 1e-12), size=(length, n_dims))
    return out + noise


def _gen_linear(length: int, n_dims: int, start_val: float, end_val: float, noise_level: float, rng) -> np.ndarray:
    """Linear trend."""
    t = np.linspace(start_val, end_val, length)
    noise = rng.normal(scale=max(0.05 * noise_level, 1e-12), size=(length, n_dims))
    return np.tile(t[:, None], (1, n_dims)) + noise


_PATTERN_GENERATORS = {
    "constant": "constant",
    "sinusoidal": "sinusoidal",
    "step": "step",
    "stairs": "stairs",
    "linear": "linear",
    "gp": "gp",
}


# -- Gaussian-process based segment (smooth, state-dependent) --


def _rbf_kernel(t: np.ndarray, lengthscale: float, variance: float = 1.0) -> np.ndarray:
    """Squared-exponential covariance matrix on a 1-D grid."""
    diff = t[:, None] - t[None, :]
    return variance * np.exp(-0.5 * (diff / max(lengthscale, 1e-3)) ** 2)


def _sample_gp(length: int, n_dims: int, lengthscale: float, variance: float, rng: np.random.Generator) -> np.ndarray:
    """Sample ``n_dims`` independent GP draws on a unit-interval grid of length ``length``.

    Uses a low-rank Cholesky with a tiny jitter for numerical stability.
    """
    if length <= 1:
        return rng.normal(size=(length, n_dims))
    t = np.linspace(0.0, 1.0, length)
    K = _rbf_kernel(t, lengthscale=lengthscale, variance=variance)
    K = K + 1e-6 * np.eye(length)
    try:
        L = np.linalg.cholesky(K)
    except np.linalg.LinAlgError:
        # Fall back to eigendecomposition if Cholesky fails
        w, V = np.linalg.eigh(K)
        w = np.clip(w, 1e-10, None)
        L = V * np.sqrt(w)
    z = rng.normal(size=(length, n_dims))
    return L @ z


def _gen_gp(
    length: int,
    n_dims: int,
    lengthscale: float,
    variance: float,
    offset: float,
    noise_level: float,
    rng: np.random.Generator,
) -> np.ndarray:
    """Smooth Gaussian-process segment with state-dependent statistics."""
    base = _sample_gp(length, n_dims, lengthscale=lengthscale, variance=variance, rng=rng)
    noise = rng.normal(scale=max(0.05 * noise_level, 1e-12), size=(length, n_dims))
    return base + offset + noise


def _generate_segment_by_pattern(
    pattern: str,
    state_idx: int,
    length: int,
    n_dims: int,
    noise_level: float,
    shape_rng: np.random.Generator,
    noise_rng: np.random.Generator | None = None,
) -> np.ndarray:
    """Generate one segment according to the chosen pattern type.

    Parameters
    ----------
    shape_rng : numpy Generator
        Drives all *shape* draws (waveform parameters, GP hyper-parameters,
        mixed-pattern choice, GP base realization). Seed it from the state id
        so that recurring segments of the same state share the same generative
        process.
    noise_rng : numpy Generator, optional
        Drives the additive observation noise. If ``None``, ``shape_rng`` is
        reused (pixel-identical recurring states). Pass a per-segment RNG to
        keep the shape consistent across recurrences while varying noise.
    """
    if noise_rng is None:
        noise_rng = shape_rng
    if pattern == "constant":
        level = shape_rng.uniform(-2, 2)
        return _gen_constant(length, n_dims, level, noise_level, noise_rng)
    elif pattern == "sinusoidal":
        amp = shape_rng.uniform(0.5, 2.0)
        freq = shape_rng.uniform(1.0, 4.0)
        phase = shape_rng.uniform(0, 1)
        offset = shape_rng.uniform(-1, 1)
        return _gen_sinusoidal(length, n_dims, amp, freq, phase, offset, noise_level, noise_rng)
    elif pattern == "step":
        n_steps = int(shape_rng.integers(2, 5))
        levels = shape_rng.uniform(-2, 2, size=n_steps).tolist()
        return _gen_step(length, n_dims, levels, noise_level, noise_rng)
    elif pattern == "stairs":
        start = shape_rng.uniform(-2, 1)
        step_size = shape_rng.uniform(0.3, 1.0) * shape_rng.choice([-1, 1])
        n_stairs = int(shape_rng.integers(3, 7))
        return _gen_stairs(length, n_dims, start, step_size, n_stairs, noise_level, noise_rng)
    elif pattern == "linear":
        s = shape_rng.uniform(-2, 2)
        e = shape_rng.uniform(-2, 2)
        return _gen_linear(length, n_dims, s, e, noise_level, noise_rng)
    elif pattern == "gp":
        # All shape draws (hyper-parameters AND base GP sample) use shape_rng,
        # so two segments sharing the same state produce the same realization.
        lengthscale = float(shape_rng.uniform(0.04, 0.20))
        variance = float(shape_rng.uniform(0.4, 1.8))
        offset = float(shape_rng.uniform(-1.5, 1.5))
        base = _sample_gp(length, n_dims, lengthscale=lengthscale, variance=variance, rng=shape_rng)
        noise = noise_rng.normal(scale=max(0.05 * noise_level, 1e-12), size=(length, n_dims))
        return base + offset + noise
    elif pattern == "mixed":
        # Pick a sub-pattern deterministically from shape_rng so two segments
        # of the same recurring state pick the SAME sub-pattern.
        choice = shape_rng.choice(["constant", "sinusoidal", "step", "stairs", "linear", "gp"])
        return _generate_segment_by_pattern(choice, state_idx, length, n_dims, noise_level, shape_rng, noise_rng)
    else:
        # Fallback to constant
        return _gen_constant(length, n_dims, float(state_idx), noise_level, noise_rng)


def generate_synthetic_series(
    length: int = 1000,
    n_segments: int = 3,
    n_dims: int = 2,
    pattern: PatternType = "gp",
    noise_level: float = 0.5,
    recurring_states: bool = False,
    min_segment_length: int = 20,
    continuous: bool = True,
    random_state: int | None = None,
) -> TimeSeriesData:
    """Generate a synthetic multivariate time series with labelled segments.

    Parameters
    ----------
    pattern : str
        Intra-segment waveform: 'constant', 'sinusoidal', 'step', 'stairs',
        'linear', 'gp' (Gaussian process, smooth and state-dependent),
        or 'mixed' (random per segment).
    recurring_states : bool
        If True, state labels can repeat (fewer distinct states than segments).
        Useful for testing state-detection algorithms.
    min_segment_length : int
        Minimum length of each segment (default 20).
    continuous : bool
        If True, shift each segment so its first value matches the last value
        of the previous segment, removing artificial discontinuities at the
        boundaries (purely cosmetic; does not affect state labels).
    """
    if length <= 0:
        raise ValueError("length must be positive")
    if n_dims <= 0:
        raise ValueError("n_dims must be positive")
    if noise_level < 0:
        raise ValueError("noise_level must be non-negative")

    rng = np.random.default_rng(random_state)
    change_points = _generate_boundaries(
        length=length,
        n_segments=n_segments,
        rng=rng,
        min_segment_length=min_segment_length,
    )
    boundaries = [0, *change_points, length]

    # Assign state labels
    if recurring_states and n_segments >= 3:
        # Use fewer distinct states than segments (at least 2)
        n_distinct = max(2, n_segments // 2)
        state_ids: list[int] = []
        for i in range(n_segments):
            # Avoid same state as previous
            candidates = list(range(n_distinct))
            if state_ids:
                candidates = [c for c in candidates if c != state_ids[-1]]
            state_ids.append(int(rng.choice(candidates)))
    else:
        state_ids = list(range(n_segments))

    states = np.zeros(length, dtype=int)
    signal = np.zeros((length, n_dims), dtype=float)

    # One seed per *distinct state* drives all shape draws (waveform params,
    # GP hyper-params, mixed sub-pattern choice). Two segments sharing the
    # same state thus share the same generative process. A separate per-segment
    # seed drives only the additive observation noise, so recurring segments
    # look alike without being pixel-identical.
    distinct_states = sorted(set(state_ids))
    state_seeds: dict[int, int] = {s: int(rng.integers(0, 2**31)) for s in distinct_states}
    noise_seeds: list[int] = [int(rng.integers(0, 2**31)) for _ in range(len(state_ids))]

    for seg_idx, (start, stop) in enumerate(zip(boundaries[:-1], boundaries[1:])):
        sid = state_ids[seg_idx]
        seg_len = stop - start

        shape_rng = np.random.default_rng(state_seeds[sid])
        noise_rng = np.random.default_rng(noise_seeds[seg_idx])

        segment = _generate_segment_by_pattern(pattern, sid, seg_len, n_dims, noise_level, shape_rng, noise_rng)

        # Stitch segment to previous endpoint to suppress visual discontinuities
        # at the boundary (does not change the state label or boundary index).
        if continuous and seg_idx > 0 and seg_len > 0:
            prev_end = signal[start - 1]  # shape (n_dims,)
            shift = prev_end - segment[0]
            segment = segment + shift

        signal[start:stop] = segment
        states[start:stop] = sid

    recur_label = ", recurring" if recurring_states else ""
    return TimeSeriesData(
        signal=signal,
        ground_truth=states,
        change_points=change_points,
        name=f"Synthetic ({pattern}{recur_label}, {n_segments} seg, {n_dims}D)",
    )


# ---------------------------------------------------------------------------
# Built-in Datasets
# ---------------------------------------------------------------------------

MOCAP_TRIALS = list(range(9))


def load_mocap_dataset(trial: int = 0) -> TimeSeriesData:
    """Load a sample CMU MoCap 86 trial from tsseg built-in datasets."""
    from tsseg.data.datasets import load_mocap

    X, y = load_mocap(trial=trial, return_X_y=True)
    X = np.asarray(X, dtype=float)
    y = np.asarray(y, dtype=int)
    return TimeSeriesData(
        signal=X,
        ground_truth=y,
        name=f"Sample dataset (CMU MoCap 86, trial {trial})",
    )


def get_builtin_datasets() -> dict[str, dict]:
    """Return available built-in datasets metadata."""
    return {
        "Sample dataset": {
            "description": (
                "A real-world trial from CMU MoCap 86 — humeral & femoral angles, 4 dimensions, 9 labelled trials."
            ),
            "loader": load_mocap_dataset,
            "params": {"trial": {"type": "int", "choices": MOCAP_TRIALS, "default": 0}},
        },
    }


# ---------------------------------------------------------------------------
# CSV Upload
# ---------------------------------------------------------------------------


def load_csv(
    file_path: str,
    separator: str = ",",
    has_header: bool = True,
    label_column: str | None = None,
) -> TimeSeriesData:
    """Load a time series from a CSV file.

    Parameters
    ----------
    file_path : str
        Path to the CSV file.
    separator : str
        Column separator.
    has_header : bool
        Whether the first row is a header.
    label_column : str or None
        Name of the ground truth column (if any).
    """
    header = 0 if has_header else None
    df = pd.read_csv(file_path, sep=separator, header=header)

    if len(df) > MAX_UPLOAD_POINTS:
        raise ValueError(
            f"File too large: {len(df)} rows (max {MAX_UPLOAD_POINTS}). Please truncate or subsample your data."
        )

    ground_truth = None
    if label_column and label_column in df.columns:
        ground_truth = df[label_column].values.astype(int)
        df = df.drop(columns=[label_column])
    elif label_column and label_column not in df.columns:
        # Try auto-detect common names
        for candidate in [
            "label",
            "labels",
            "ground_truth",
            "gt",
            "state",
            "states",
            "class",
            "segment",
            "is_anomaly",
            "anomaly",
            "target",
            "y",
        ]:
            if candidate in df.columns:
                ground_truth = df[candidate].values.astype(int)
                df = df.drop(columns=[candidate])
                break
    else:
        # No label_column specified — still try auto-detect
        for candidate in [
            "label",
            "labels",
            "ground_truth",
            "gt",
            "state",
            "states",
            "class",
            "segment",
            "is_anomaly",
            "anomaly",
            "target",
            "y",
        ]:
            if candidate in df.columns:
                ground_truth = df[candidate].values.astype(int)
                df = df.drop(columns=[candidate])
                break

    # Drop common index / timestamp columns that are not signal data
    _INDEX_COLS = {
        "timestamp",
        "timestamps",
        "time",
        "date",
        "datetime",
        "index",
        "idx",
        "id",
        "row",
        "step",
    }
    cols_to_drop = [c for c in df.columns if str(c).lower().strip() in _INDEX_COLS]
    if cols_to_drop:
        df = df.drop(columns=cols_to_drop)

    # Drop non-numeric columns
    numeric_df = df.select_dtypes(include=[np.number])
    if numeric_df.empty:
        raise ValueError("No numeric columns found in the CSV file.")

    signal = numeric_df.values.astype(float)

    # Check for NaN
    nan_ratio = np.isnan(signal).mean()
    if nan_ratio > 0.1:
        raise ValueError(f"Too many NaN values ({nan_ratio:.1%}). Please clean your data.")
    if nan_ratio > 0:
        # Forward-fill NaN
        df_filled = pd.DataFrame(signal).ffill().bfill()
        signal = df_filled.values

    return TimeSeriesData(
        signal=signal,
        ground_truth=ground_truth,
        name="Uploaded CSV",
    )