"""Shared constants and small layout helpers for the viewer widgets."""

from PyQt6.QtCore import Qt
from PyQt6.QtWidgets import (
    QDoubleSpinBox, QFormLayout, QFrame, QGroupBox, QLabel, QScrollArea,
    QSizePolicy, QVBoxLayout, QWidget,
)

from sras_format import CH1_IDX, CH3_IDX, CH4_IDX

# ---------------------------------------------------------------------------
# Display constants
# ---------------------------------------------------------------------------

CH_LABELS = [
    "CH1 — RF (FFT peak freq)",
    "CH3 — Bias A (DC mean)",
    "CH4 — Bias B (DC mean)",
    "CH1 — Velocity (SRAS)",
]

# Combo index for the derived velocity mode (uses CH1_IDX data)
VELOCITY_MODE_IDX = 3
# All modes that operate on CH1 waveforms
CH1_DERIVED_MODES = (CH1_IDX, VELOCITY_MODE_IDX)

CMAPS = ["gray", "viridis", "plasma", "inferno", "hot", "jet", "RdBu_r", "seismic"]

# (mode_str, status-bar unit, colorbar label) per channel index
_CHANNEL_DISPLAY = {
    CH1_IDX: ("RF", "Peak frequency (MHz)", "MHz"),
    CH3_IDX: ("DC", "DC mean (mV)", "mV"),
    CH4_IDX: ("DC", "DC mean (mV)", "mV"),
    VELOCITY_MODE_IDX: ("Velocity", "Velocity (m/s)", "m/s"),
}

_CSS_HINT = "font-size: 11px; color: #aaa;"
_CSS_INFO = "font-size: 11px;"
_CSS_MUTED = "color: #888; font-size: 11px;"
_CSS_WARN = "color: #e07000; font-size: 11px;"
_CSS_BUSY = "color: #4a90d9; font-size: 11px;"

# Side-panel column widths (the scroll areas that hold the controls).
_LEFT_PANEL_W = 288
_RIGHT_PANEL_W = 272

# Minimum width for a spin box so its value + suffix are never clipped.
_SPIN_MIN_W = 96


# ---------------------------------------------------------------------------
# Small layout helpers
# ---------------------------------------------------------------------------

class Jobs:
    """Keys for SrasViewerWindow's background-job registry (_run_worker /
    _job_running) and its progress dialogs — one place instead of string
    literals scattered across window and dialogs."""
    LOAD = "load"
    COMPUTE = "compute"
    DC_PRECOMPUTE = "dc_precompute"
    BATCH = "batch"
    # The alignment wizard's three background steps: fetching each angle's CH4
    # image for the mask stack, registering the angles, and writing the aligned
    # export. Separate keys because a retry of one must not be blocked by
    # another having run, and _run_worker's busy check is per key.
    ALIGN_MASKS = "align_masks"
    ALIGN_CORRELATE = "align_correlate"
    ALIGN_EXPORT = "align_export"


def _make_dspin(lo: float, hi: float, decimals: int, *, suffix: str = "",
                value: float | None = None, step: float | None = None) -> QDoubleSpinBox:
    """A QDoubleSpinBox with the panel-standard construction."""
    spin = QDoubleSpinBox()
    spin.setRange(lo, hi)
    spin.setDecimals(decimals)
    if suffix:
        spin.setSuffix(suffix)
    if step is not None:
        spin.setSingleStep(step)
    if value is not None:
        spin.setValue(value)
    spin.setMinimumWidth(_SPIN_MIN_W)
    return spin


def _axes_extent(x_axis, y_axis, dx: float, dy: float) -> list[float]:
    """Matplotlib imshow extent with half-pixel margins, Y flipped so row 0
    renders at the top."""
    return [x_axis[0] - dx / 2, x_axis[-1] + dx / 2,
            y_axis[-1] + dy / 2, y_axis[0] - dy / 2]


def _wrap_label(text: str = "", css: str | None = None) -> QLabel:
    """A word-wrapped QLabel that reports its *wrapped* height to the layout.

    A plain word-wrapped QLabel advertises a single-line minimum height, so in a
    fixed-width column the layout happily shrinks it and the extra lines get
    clipped.  Enabling height-for-width makes the box layout ask for the real
    height at the column's width instead.
    """
    lbl = QLabel(text)
    lbl.setWordWrap(True)
    sp = lbl.sizePolicy()
    sp.setVerticalPolicy(QSizePolicy.Policy.Minimum)
    sp.setHeightForWidth(True)
    lbl.setSizePolicy(sp)
    if css:
        lbl.setStyleSheet(css)
    return lbl


def _group(title: str) -> tuple[QGroupBox, QVBoxLayout]:
    """A group box with consistent, non-cramped internal margins."""
    grp = QGroupBox(title)
    lay = QVBoxLayout(grp)
    lay.setContentsMargins(10, 8, 10, 10)
    lay.setSpacing(6)
    return grp, lay


def _form() -> QFormLayout:
    """A label/field form layout for a narrow side panel."""
    form = QFormLayout()
    form.setContentsMargins(0, 0, 0, 0)
    form.setHorizontalSpacing(8)
    form.setVerticalSpacing(6)
    form.setLabelAlignment(Qt.AlignmentFlag.AlignRight
                           | Qt.AlignmentFlag.AlignVCenter)
    form.setFormAlignment(Qt.AlignmentFlag.AlignLeft | Qt.AlignmentFlag.AlignTop)
    form.setFieldGrowthPolicy(
        QFormLayout.FieldGrowthPolicy.AllNonFixedFieldsGrow)
    form.setRowWrapPolicy(QFormLayout.RowWrapPolicy.DontWrapRows)
    return form


def _scroll_panel(inner: QWidget, width: int) -> QScrollArea:
    """Put a side panel in a fixed-width scroll area.

    Without this the panels are sized by the window: a short window squeezes the
    controls past their minimum heights, which is what makes text overlap the
    widget below it.  Scrolling keeps every control at its natural size.
    """
    area = QScrollArea()
    area.setWidget(inner)
    area.setWidgetResizable(True)
    area.setFrameShape(QFrame.Shape.NoFrame)
    area.setHorizontalScrollBarPolicy(Qt.ScrollBarPolicy.ScrollBarAlwaysOff)
    area.setVerticalScrollBarPolicy(Qt.ScrollBarPolicy.ScrollBarAsNeeded)
    area.setFixedWidth(width)
    area.viewport().setAutoFillBackground(False)
    inner.setAutoFillBackground(False)
    return area