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

from PyQt6.QtCore import Qt
from PyQt6.QtWidgets import (
    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
# ---------------------------------------------------------------------------

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