"""Shared chart styling: palette, matplotlib defaults and figure saving."""

from pathlib import Path

import matplotlib as mpl
import matplotlib.pyplot as plt

# --- Diverging poles for sentiment polarity ---
NEGATIVE = "#e34948"   # red pole
NEUTRAL = "#898781"    # neutral gray midpoint
POSITIVE = "#2a78d6"   # blue pole

#: Sentiment label -> colour.
SENTIMENT_COLORS = {
    "Negative": NEGATIVE,
    "Neutral": NEUTRAL,
    "Positive": POSITIVE,
}

# --- Categorical slots (first three validate on all pairs) ---
SERIES = ("#2a78d6", "#eb6834", "#1baf7a")

# --- Sequential blue ramp, light -> dark (magnitude) ---
SEQUENTIAL = ["#cde2fb", "#b7d3f6", "#9ec5f4", "#86b6ef", "#6da7ec",
              "#5598e7", "#3987e5", "#2a78d6", "#256abf", "#1c5cab",
              "#184f95", "#104281", "#0d366b"]

# --- Chrome and ink ---
SURFACE = "#fcfcfb"
INK = "#0b0b0b"
INK_SECONDARY = "#52514e"
INK_MUTED = "#898781"
GRIDLINE = "#e1e0d9"
BASELINE = "#c3c2b7"
ACCENT = "#2a78d6"

#: Default folder for saved charts.
PLOTS_SUBDIR = "plots"


def sequential_cmap():
    """Return the one-hue blue ramp as a matplotlib colormap."""
    return mpl.colors.LinearSegmentedColormap.from_list("asa_blue", SEQUENTIAL)


def apply_chart_style():
    """Set matplotlib defaults: thin marks, hairline solid grid, recessive axes."""
    mpl.rcParams.update({
        "figure.facecolor": SURFACE,
        "axes.facecolor": SURFACE,
        "savefig.facecolor": SURFACE,
        "font.family": ["DejaVu Sans"],
        "font.size": 10,
        "text.color": INK,
        "axes.labelcolor": INK_SECONDARY,
        "axes.edgecolor": BASELINE,
        "axes.linewidth": 0.8,
        "axes.titlecolor": INK,
        "axes.titlesize": 12,
        "axes.titleweight": "normal",   # DejaVu has no medium; avoids a warning
        "axes.titlepad": 12,
        "axes.grid": True,
        "axes.axisbelow": True,
        "grid.color": GRIDLINE,
        "grid.linewidth": 0.8,
        "grid.linestyle": "-",          # never dashed - dashes read as a threshold
        "xtick.color": INK_MUTED,
        "ytick.color": INK_MUTED,
        "xtick.labelcolor": INK_SECONDARY,
        "ytick.labelcolor": INK_SECONDARY,
        "xtick.direction": "out",
        "ytick.direction": "out",
        "legend.frameon": False,
        "legend.fontsize": 9,
        "figure.autolayout": False,
    })


def strip_spines(ax, keep=("left", "bottom")):
    """Remove chart-junk spines, keeping only the ones that carry meaning."""
    for side, spine in ax.spines.items():
        spine.set_visible(side in keep)


def finish(fig, save_path=None, show=True, dpi=150):
    """Save and/or show ``fig``, then close it when it is not being shown."""
    fig.tight_layout()

    written = None
    if save_path is not None:
        written = Path(save_path)
        written.parent.mkdir(parents=True, exist_ok=True)
        fig.savefig(written, dpi=dpi, bbox_inches="tight")

    if show:
        plt.show()
    else:
        plt.close(fig)

    return written