src/explicit_learning/renderers/plot.py

"""Deterministic, information-complete plot rendering.

``PlotRenderer`` draws directly from ``plot_world_v1`` with Pillow.  Unlike the
initial marker-only prototype, the image contains the information a solver needs:
numeric or categorical x ticks, numeric y ticks, title/axis labels, a
series-coloured legend, and line or grouped-bar geometry.

Redacted points are never placed at their hidden y coordinate.  A fixed vertical
strip at the point's observed x spans the complete data region, and the hidden
point breaks its line.  Axis scaling uses ``world["render_domain"]`` when present;
otherwise it is derived from visible points only.  Consequently completion worlds
that differ only in a hidden y value produce byte-identical pixel assets.
"""

from __future__ import annotations

import io
from collections.abc import Iterable, Mapping, Sequence
from dataclasses import dataclass
from fractions import Fraction
from math import ceil, floor
from typing import Any

from ..dsl.ast import canonical_number_str, parse_number
from ..sources.base import World
from ..sources.world_ops import hidden_nodes
from .base import (
    GlyphRecord,
    RenderedAssets,
    RendererFamily,
    RendererKind,
    RenderError,
    _encode_uint32_png,
    build_render_manifest,
    build_text_manifest,
    font_sha256,
    validate_rendered_assets,
)

_NAME = "plot_renderer"
_VERSION = "3"
_KIND: RendererKind = "plot"
_MIN_WIDTH = 320
_MIN_HEIGHT = 220
_Y_TICKS = 5
_MAX_X_TICKS = 16


@dataclass(frozen=True)
class _Point:
    node_id: str
    x_label: str
    x_value: Fraction | None
    y: Fraction | None
    y_label: str
    hidden: bool


@dataclass(frozen=True)
class _Series:
    node_id: str
    label: str
    points: tuple[_Point, ...]
    hidden: bool


@dataclass(frozen=True)
class _Domain:
    numeric_x: bool
    x_min: Fraction
    x_max: Fraction
    y_min: Fraction
    y_max: Fraction
    x_labels: tuple[str, ...]

    def manifest_record(self) -> dict[str, Any]:
        return {
            "numeric_x": self.numeric_x,
            "x_min": canonical_number_str(self.x_min) if self.numeric_x else None,
            "x_max": canonical_number_str(self.x_max) if self.numeric_x else None,
            "y_min": canonical_number_str(self.y_min),
            "y_max": canonical_number_str(self.y_max),
            "x_labels": list(self.x_labels),
        }


class _Canvas:
    """Pillow RGBA canvas plus a same-pass integer owner canvas."""

    def __init__(self, width: int, height: int, family: RendererFamily) -> None:
        import numpy as np
        from matplotlib.font_manager import findfont
        from PIL import Image, ImageDraw

        self.width = width
        self.height = height
        self.family = family
        self.image = Image.new("RGBA", (width, height), family.palette.get("background", "#FFFFFF"))
        self.owner_image = Image.new("I", (width, height), 0)
        self.draw = ImageDraw.Draw(self.image)
        self.owner_draw = ImageDraw.Draw(self.owner_image)
        self.owner_ids: list[str] = []
        self.owner_index: dict[str, int] = {}
        self.glyphs: list[GlyphRecord] = []
        self._font_path = findfont(family.font_name, fallback_to_default=False)
        self._font_sha256 = font_sha256(family.font_name)
        self._font_cache: dict[int, Any] = {}
        self._np = np

    def _owner(self, node_id: str) -> int:
        index = self.owner_index.get(node_id)
        if index is None:
            self.owner_ids.append(node_id)
            index = len(self.owner_ids)
            self.owner_index[node_id] = index
        return index

    def reserve(self, node_id: str) -> None:
        self._owner(node_id)

    def font(self, size: int) -> Any:
        from PIL import ImageFont

        size = max(7, int(size))
        font = self._font_cache.get(size)
        if font is None:
            font = ImageFont.truetype(self._font_path, size=size)
            self._font_cache[size] = font
        return font

    def line(
        self,
        node_id: str,
        xy: Sequence[tuple[float, float]],
        *,
        fill: str,
        width: int,
    ) -> None:
        index = self._owner(node_id)
        self.draw.line(xy, fill=fill, width=width, joint="curve")
        self.owner_draw.line(xy, fill=index, width=max(1, width))

    def rectangle(
        self,
        node_id: str | None,
        box: tuple[float, float, float, float],
        *,
        fill: str,
        outline: str | None = None,
        width: int = 1,
    ) -> None:
        self.draw.rectangle(box, fill=fill, outline=outline, width=width)
        index = 0 if node_id is None else self._owner(node_id)
        self.owner_draw.rectangle(box, fill=index)

    def ellipse(
        self,
        node_id: str,
        box: tuple[float, float, float, float],
        *,
        fill: str,
        outline: str,
        width: int = 1,
    ) -> None:
        index = self._owner(node_id)
        self.draw.ellipse(box, fill=fill, outline=outline, width=width)
        self.owner_draw.ellipse(box, fill=index)

    def text(
        self,
        node_id: str,
        text: str,
        xy: tuple[float, float],
        *,
        size: int,
        fill: str,
        anchor: str,
        max_width: float | None = None,
    ) -> tuple[int, int, int, int] | None:
        if not text:
            return None
        index = self._owner(node_id)
        x, y, font, bbox = self._text_layout(
            text,
            xy,
            size=size,
            anchor=anchor,
            max_width=max_width,
        )
        self.draw.text((x, y), text, font=font, fill=fill, anchor=anchor)
        self.owner_draw.text((x, y), text, font=font, fill=index, anchor=anchor)
        self.glyphs.append(
            GlyphRecord(
                node_id=node_id,
                text=text,
                x0=bbox[0] / self.width,
                y0=(self.height - bbox[3]) / self.height,
                x1=bbox[2] / self.width,
                y1=(self.height - bbox[1]) / self.height,
                font_sha256=self._font_sha256,
            )
        )
        return bbox

    def text_bbox(
        self,
        text: str,
        xy: tuple[float, float],
        *,
        size: int,
        anchor: str,
        max_width: float | None = None,
    ) -> tuple[int, int, int, int]:
        """Measure text exactly as :meth:`text` will draw it, without painting."""
        _, _, _, bbox = self._text_layout(
            text,
            xy,
            size=size,
            anchor=anchor,
            max_width=max_width,
        )
        return bbox

    def _text_layout(
        self,
        text: str,
        xy: tuple[float, float],
        *,
        size: int,
        anchor: str,
        max_width: float | None,
    ) -> tuple[float, float, Any, tuple[int, int, int, int]]:
        font_size = size
        font = self.font(font_size)
        if max_width is not None:
            while font_size > 7:
                probe = self.draw.textbbox(xy, text, font=font, anchor=anchor)
                if probe[2] - probe[0] <= max_width:
                    break
                font_size -= 1
                font = self.font(font_size)

        x, y = xy
        bbox = self.draw.textbbox((x, y), text, font=font, anchor=anchor)
        if max_width is not None and bbox[2] - bbox[0] > max_width + 1:
            raise RenderError(f"plot text does not fit its allotted width: {text!r}")

        # Keep the complete glyph box within the raster while preserving its
        # requested alignment as closely as possible.
        if bbox[0] < 2:
            x += 2 - bbox[0]
        if bbox[2] > self.width - 2:
            x -= bbox[2] - (self.width - 2)
        if bbox[1] < 2:
            y += 2 - bbox[1]
        if bbox[3] > self.height - 2:
            y -= bbox[3] - (self.height - 2)
        raw_bbox = self.draw.textbbox((x, y), text, font=font, anchor=anchor)
        bbox = (
            floor(raw_bbox[0]),
            floor(raw_bbox[1]),
            ceil(raw_bbox[2]),
            ceil(raw_bbox[3]),
        )
        if bbox[0] < 0 or bbox[1] < 0 or bbox[2] > self.width or bbox[3] > self.height:
            raise RenderError(f"plot glyph is outside the canvas: {text!r}, bbox={bbox!r}")
        return x, y, font, bbox

    def finish(self) -> tuple[bytes, bytes, dict[str, int]]:
        owner_array = self._np.asarray(self.owner_image, dtype="<u4")
        rgba_buf = io.BytesIO()
        self.image.save(rgba_buf, format="PNG", compress_level=9, optimize=False)
        counts = {
            node_id: int(self._np.count_nonzero(owner_array == index))
            for node_id, index in self.owner_index.items()
        }
        return rgba_buf.getvalue(), _encode_uint32_png(owner_array), counts


class PlotRenderer:
    """Deterministic renderer for ``plot_world_v1``."""

    name = _NAME
    version = _VERSION
    kind = _KIND

    def render(
        self,
        world: World,
        *,
        renderer_id: str,
        seed: int,
        width: int,
        height: int,
        family: RendererFamily | None = None,
    ) -> RenderedAssets:
        if world.get("world_schema") != "plot_world_v1":
            raise RenderError(
                f"plot renderer expects plot_world_v1, got {world.get('world_schema')!r}"
            )
        family = family or _PLOT_TRAIN_FAMILY
        if family.kind != self.kind:
            raise RenderError(
                f"renderer family {family.name!r} has kind {family.kind!r}, expected {self.kind!r}"
            )
        if renderer_id != family.name:
            raise RenderError(f"renderer_id {renderer_id!r} does not match family {family.name!r}")
        if width < _MIN_WIDTH or height < _MIN_HEIGHT:
            raise RenderError(
                f"plot canvas must be at least {_MIN_WIDTH}x{_MIN_HEIGHT}, got {width}x{height}"
            )

        series = _parse_series(world)
        domain = _build_domain(world, series)
        canvas = _Canvas(width, height, family)
        visible = _draw_plot(canvas, world, series, domain, family)
        rgba_png, node_map_png, counts = canvas.finish()

        manifest = build_render_manifest(
            renderer_id=renderer_id,
            renderer_name=self.name,
            renderer_version=self.version,
            family=family,
            world=world,
            seed=seed,
            width=width,
            height=height,
            rgba_png=rgba_png,
            node_map_png=node_map_png,
            visible_node_ids=visible,
            owner_ids=canvas.owner_ids,
            node_pixel_counts=counts,
            glyph_count=len(canvas.glyphs),
            backend="pillow",
            backend_version=_pillow_version(),
        )
        manifest["render_domain"] = domain.manifest_record()
        manifest["plot_type"] = _plot_type(world)
        assets = RenderedAssets(
            rgba_png=rgba_png,
            node_map_png=node_map_png,
            render_manifest=manifest,
            text_manifest=build_text_manifest(canvas.glyphs, world=world),
        )
        validate_rendered_assets(assets)
        return assets


def _parse_series(world: World) -> tuple[_Series, ...]:
    hidden = hidden_nodes(world)
    raw_series = world.get("series", []) or []
    if not isinstance(raw_series, list) or not raw_series:
        raise RenderError("plot world has no series")
    output: list[_Series] = []
    seen: set[str] = set()
    for raw in raw_series:
        if not isinstance(raw, Mapping):
            raise RenderError("plot series is not an object")
        sid = str(raw.get("id", ""))
        if not sid or sid in seen:
            raise RenderError(f"plot series has a missing/duplicate id: {sid!r}")
        seen.add(sid)
        is_series_hidden = sid in hidden
        points: list[_Point] = []
        raw_points = raw.get("points", []) or []
        if not isinstance(raw_points, list):
            raise RenderError(f"plot series {sid!r} points are not a list")
        for raw_point in raw_points:
            if not isinstance(raw_point, Mapping):
                raise RenderError(f"plot series {sid!r} contains a non-object point")
            pid = str(raw_point.get("id", ""))
            if not pid or pid in seen:
                raise RenderError(f"plot point has a missing/duplicate id: {pid!r}")
            seen.add(pid)
            x_label = str(raw_point.get("x", ""))
            if not x_label:
                raise RenderError(f"plot point {pid!r} has no x value")
            try:
                x_value: Fraction | None = parse_number(x_label)
            except (TypeError, ValueError, ZeroDivisionError):
                x_value = None
            is_hidden = is_series_hidden or pid in hidden
            if is_hidden:
                # A redacted point's content is deliberately opaque to layout.
                # In particular, ``None`` and alternate completion values must
                # produce the same observed raster.
                y: Fraction | None = None
                y_label = ""
            else:
                try:
                    y = parse_number(raw_point.get("y", ""))
                except (TypeError, ValueError, ZeroDivisionError) as exc:
                    raise RenderError(f"plot point {pid!r} has an invalid y value") from exc
                y_label = _exact_value_label(y)
            points.append(
                _Point(
                    node_id=pid,
                    x_label=x_label,
                    x_value=x_value,
                    y=y,
                    y_label=y_label,
                    hidden=is_hidden,
                )
            )
        output.append(
            _Series(
                node_id=sid,
                label=str(raw.get("label", sid)),
                points=tuple(points),
                hidden=is_series_hidden,
            )
        )
    if not any(s.points for s in output):
        raise RenderError("plot world has no points")
    return tuple(output)


def _build_domain(world: World, series: Sequence[_Series]) -> _Domain:
    all_points = [point for item in series for point in item.points]
    numeric_x = all(point.x_value is not None for point in all_points)
    axis_values = _axis_values(world.get("x_axis"))
    x_labels = _dedup([*axis_values, *(point.x_label for point in all_points)])
    if not x_labels:
        raise RenderError("plot world has no x labels")

    render_domain = world.get("render_domain")
    domain_map = render_domain if isinstance(render_domain, Mapping) else {}

    if numeric_x:
        numeric_values = [point.x_value for point in all_points if point.x_value is not None]
        x_min_override = _domain_bound(domain_map, "x", "min")
        x_max_override = _domain_bound(domain_map, "x", "max")
        x_min = x_min_override if x_min_override is not None else min(numeric_values)
        x_max = x_max_override if x_max_override is not None else max(numeric_values)
    else:
        x_min = Fraction(0)
        x_max = Fraction(max(1, len(x_labels) - 1))
    x_min, x_max = _nondegenerate(x_min, x_max)

    visible_y = [
        point.y
        for item in series
        if not item.hidden
        for point in item.points
        if not point.hidden and point.y is not None
    ]
    y_min_override = _domain_bound(domain_map, "y", "min")
    y_max_override = _domain_bound(domain_map, "y", "max")
    if visible_y:
        y_min = y_min_override if y_min_override is not None else min(visible_y)
        y_max = y_max_override if y_max_override is not None else max(visible_y)
    else:
        y_min = y_min_override if y_min_override is not None else Fraction(0)
        y_max = y_max_override if y_max_override is not None else Fraction(1)

    if "bar" in _plot_type(world) and y_min_override is None and y_max_override is None:
        y_min = min(y_min, Fraction(0))
        y_max = max(y_max, Fraction(0))
    y_min, y_max = _nondegenerate(y_min, y_max)
    if y_min_override is None and y_max_override is None:
        padding = (y_max - y_min) / 10
        y_min -= padding
        y_max += padding

    return _Domain(
        numeric_x=numeric_x,
        x_min=x_min,
        x_max=x_max,
        y_min=y_min,
        y_max=y_max,
        x_labels=tuple(x_labels),
    )


def _draw_plot(
    canvas: _Canvas,
    world: World,
    series: Sequence[_Series],
    domain: _Domain,
    family: RendererFamily,
) -> tuple[str, ...]:
    width, height = canvas.width, canvas.height
    legend_width = max(118, min(210, int(width * 0.24)))
    left = max(62, int(width * 0.11))
    right = width - legend_width
    top = max(54, int(height * 0.12))
    bottom = height - max(58, int(height * 0.15))
    if right - left < 140 or bottom - top < 100:
        raise RenderError("plot canvas leaves insufficient data area after labels/legend")

    text_color = family.palette.get("text", "#202020")
    axis_color = family.palette.get("axis", "#444444")
    grid_color = family.palette.get("grid", "#D8D8D8")
    plot_type = _plot_type(world)
    visible_series_count = sum(not item.hidden for item in series)
    x_padding = 0.0
    if "bar" in plot_type:
        _, bar_width = _bar_dimensions(canvas.width, len(domain.x_labels), visible_series_count)
        x_padding = ((max(1, visible_series_count) - 1) / 2 + 0.42) * bar_width + 2
    x_span = right - left - 2 * x_padding
    if x_span <= 0:
        raise RenderError("plot data area is too narrow for grouped bars")

    # Title and axis captions.
    title = _display_text(world.get("title")) or "Chart"
    x_axis_label = _axis_label(world.get("x_axis")) or "X"
    y_axis_label = _axis_label(world.get("y_axis")) or "Value"
    canvas.text(
        "plot:title",
        title,
        (width / 2, 18),
        size=max(14, min(20, width // 45)),
        fill=text_color,
        anchor="ma",
        max_width=width - 20,
    )
    canvas.text(
        "axis:y:label",
        y_axis_label,
        (left, top - 9),
        size=11,
        fill=text_color,
        anchor="ld",
        max_width=max(80, (right - left) * 0.45),
    )
    canvas.text(
        "axis:x:label",
        x_axis_label,
        ((left + right) / 2, height - 8),
        size=11,
        fill=text_color,
        anchor="md",
        max_width=right - left,
    )

    def x_position(point: _Point) -> float:
        if domain.numeric_x:
            assert point.x_value is not None
            ratio = float((point.x_value - domain.x_min) / (domain.x_max - domain.x_min))
        else:
            ratio = (
                domain.x_labels.index(point.x_label) / (len(domain.x_labels) - 1)
                if len(domain.x_labels) > 1
                else 0.5
            )
        if ratio < -1e-9 or ratio > 1 + 1e-9:
            raise RenderError(f"x value {point.x_label!r} is outside render_domain")
        return left + x_padding + min(1.0, max(0.0, ratio)) * x_span

    def x_label_position(label: str) -> float:
        if domain.numeric_x:
            value = parse_number(label)
            ratio = float((value - domain.x_min) / (domain.x_max - domain.x_min))
        else:
            ratio = (
                domain.x_labels.index(label) / (len(domain.x_labels) - 1)
                if len(domain.x_labels) > 1
                else 0.5
            )
        return left + x_padding + min(1.0, max(0.0, ratio)) * x_span

    def y_position(value: Fraction) -> float:
        ratio = float((value - domain.y_min) / (domain.y_max - domain.y_min))
        if ratio < -1e-9 or ratio > 1 + 1e-9:
            raise RenderError(f"y value {canonical_number_str(value)!r} is outside render_domain")
        return bottom - min(1.0, max(0.0, ratio)) * (bottom - top)

    # Grid, axes, and numeric y ticks.
    for i in range(_Y_TICKS):
        ratio = Fraction(i, _Y_TICKS - 1)
        value = domain.y_min + ratio * (domain.y_max - domain.y_min)
        y = bottom - float(ratio) * (bottom - top)
        node_id = f"axis:y:tick:{i}"
        canvas.line(node_id, [(left, y), (right, y)], fill=grid_color, width=1)
        canvas.text(
            node_id,
            _format_number(value),
            (left - 7, y),
            size=9,
            fill=text_color,
            anchor="rm",
            max_width=left - 12,
        )
    canvas.line("axis:x", [(left, bottom), (right, bottom)], fill=axis_color, width=2)
    canvas.line("axis:y", [(left, top), (left, bottom)], fill=axis_color, width=2)

    tick_labels = _decimate(domain.x_labels, _MAX_X_TICKS)
    spacing = (right - left) / max(1, len(tick_labels) - 1)
    tick_size = max(7, min(10, int(spacing * 0.28)))
    for i, label in enumerate(tick_labels):
        x = x_label_position(label)
        node_id = f"axis:x:tick:{i}"
        canvas.line(node_id, [(x, bottom), (x, bottom + 5)], fill=axis_color, width=1)
        canvas.text(
            node_id,
            label,
            (x, bottom + 8 + (i % 2) * 10),
            size=tick_size,
            fill=text_color,
            anchor="ma",
            max_width=max(24, spacing * 1.8),
        )

    # The redaction token is anchored only at observed x.  It is painted after
    # the grid (and clears grid ownership) but before visible series, so unrelated
    # visible points at the same x remain readable.
    hidden_x = _dedup(point.x_label for item in series for point in item.points if point.hidden)
    strip_half_width = max(4, min(12, int((right - left) / max(24, len(domain.x_labels) * 8))))
    for label in hidden_x:
        prototype = next(
            point for item in series for point in item.points if point.x_label == label
        )
        x = x_position(prototype)
        canvas.rectangle(
            None,
            (x - strip_half_width, top, x + strip_half_width, bottom),
            fill=family.palette.get("redact", "#111111"),
        )

    colours = _series_colours(family)
    visible: list[str] = []

    # Reserve every visible semantic owner before drawing; this makes node-table
    # order independent of accidental primitive ordering.
    for item in series:
        if item.hidden:
            continue
        visible.append(item.node_id)
        canvas.reserve(item.node_id)
        for point in item.points:
            if not point.hidden:
                visible.append(point.node_id)
                canvas.reserve(point.node_id)

    if "bar" in plot_type:
        _draw_bars(canvas, series, domain, x_position, y_position, colours)
    else:
        _draw_lines(canvas, series, x_position, y_position, colours, scatter="scatter" in plot_type)
    _draw_value_labels(
        canvas,
        series,
        domain,
        x_position,
        y_position,
        colours,
        plot_type=plot_type,
        data_bounds=(left, top, right, bottom),
    )

    # Series-coloured legend.  The swatch and text are both owned by the series,
    # guaranteeing coverage even for a single-point series.
    legend_x = right + 17
    legend_y = top + 8
    visible_series = [item for item in series if not item.hidden]
    row_height = max(18, min(28, (bottom - top) // max(1, len(visible_series))))
    for index, item in enumerate(visible_series):
        y = legend_y + index * row_height
        if y + 13 > bottom:
            raise RenderError("plot legend does not fit within the canvas")
        colour = colours[index % len(colours)]
        canvas.rectangle(
            item.node_id,
            (legend_x, y, legend_x + 18, y + 8),
            fill=colour,
            outline=axis_color,
        )
        canvas.text(
            item.node_id,
            item.label,
            (legend_x + 24, y + 4),
            size=10,
            fill=text_color,
            anchor="lm",
            max_width=width - (legend_x + 28) - 4,
        )

    return tuple(_dedup(visible))


def _draw_lines(
    canvas: _Canvas,
    series: Sequence[_Series],
    x_position: Any,
    y_position: Any,
    colours: Sequence[str],
    *,
    scatter: bool,
) -> None:
    visible_series = [item for item in series if not item.hidden]
    count = len(visible_series)
    for series_index, item in enumerate(visible_series):
        colour = colours[series_index % len(colours)]
        x_offset = (series_index - (count - 1) / 2) * min(4.0, 8.0 / max(1, count))
        run: list[tuple[float, float]] = []
        runs: list[list[tuple[float, float]]] = []
        for point in item.points:
            if point.hidden:
                if len(run) >= 2:
                    runs.append(run)
                run = []
                continue
            assert point.y is not None
            run.append((x_position(point) + x_offset, y_position(point.y)))
        if len(run) >= 2:
            runs.append(run)
        if not scatter:
            for coordinates in runs:
                canvas.line(item.node_id, coordinates, fill=colour, width=3)
        for point_index, point in enumerate(point for point in item.points if not point.hidden):
            assert point.y is not None
            x = x_position(point) + x_offset
            y = y_position(point.y)
            radius = max(3.0, 6.0 - series_index * 0.35 + (point_index % 2) * 0.2)
            canvas.ellipse(
                point.node_id,
                (x - radius, y - radius, x + radius, y + radius),
                fill=colour,
                outline="#202020",
                width=1,
            )


def _draw_bars(
    canvas: _Canvas,
    series: Sequence[_Series],
    domain: _Domain,
    x_position: Any,
    y_position: Any,
    colours: Sequence[str],
) -> None:
    visible_series = [item for item in series if not item.hidden]
    count = max(1, len(visible_series))
    _, bar_width = _bar_dimensions(canvas.width, len(domain.x_labels), count)
    baseline_value = min(max(Fraction(0), domain.y_min), domain.y_max)
    baseline = y_position(baseline_value)
    for series_index, item in enumerate(visible_series):
        colour = colours[series_index % len(colours)]
        offset = (series_index - (count - 1) / 2) * bar_width
        for point in item.points:
            if point.hidden:
                continue
            assert point.y is not None
            x = x_position(point) + offset
            y = y_position(point.y)
            y0, y1 = sorted((baseline, y))
            if y1 - y0 < 1:
                y1 = y0 + 1
            canvas.rectangle(
                point.node_id,
                (x - bar_width * 0.42, y0, x + bar_width * 0.42, y1),
                fill=colour,
                outline="#202020",
            )


def _draw_value_labels(
    canvas: _Canvas,
    series: Sequence[_Series],
    domain: _Domain,
    x_position: Any,
    y_position: Any,
    colours: Sequence[str],
    *,
    plot_type: str,
    data_bounds: tuple[float, float, float, float],
) -> None:
    """Draw every visible point's exact value with deterministic collision avoidance."""
    left, top, right, bottom = data_bounds
    visible_series = [item for item in series if not item.hidden]
    count = max(1, len(visible_series))
    if "bar" in plot_type:
        _, bar_width = _bar_dimensions(canvas.width, len(domain.x_labels), count)
        x_offsets = [(series_index - (count - 1) / 2) * bar_width for series_index in range(count)]
    else:
        x_offsets = [
            (series_index - (count - 1) / 2) * min(4.0, 8.0 / count)
            for series_index in range(count)
        ]

    # Marker boxes are obstacles for line/scatter labels. Bar labels naturally
    # sit beyond the value endpoint and do not need the whole bar as an obstacle.
    occupied: list[tuple[int, int, int, int]] = []
    if "bar" not in plot_type:
        for series_index, item in enumerate(visible_series):
            for point in item.points:
                if point.hidden:
                    continue
                assert point.y is not None
                x = x_position(point) + x_offsets[series_index]
                y = y_position(point.y)
                occupied.append((round(x - 7), round(y - 7), round(x + 7), round(y + 7)))

    background = canvas.family.palette.get("background", "#FFFFFF")
    base_size = max(8, min(10, canvas.width // 72))
    max_width = min(190.0, max(40.0, right - left - 8))
    for series_index, item in enumerate(visible_series):
        colour = colours[series_index % len(colours)]
        for point_index, point in enumerate(point for point in item.points if not point.hidden):
            assert point.y is not None
            if not point.y_label:
                raise RenderError(f"visible point {point.node_id!r} has no exact value label")
            x = x_position(point) + x_offsets[series_index]
            y = y_position(point.y)
            candidates = _value_label_candidates(
                x,
                y,
                data_bounds=data_bounds,
                parity=(series_index + point_index) % 2,
            )

            selected: (
                tuple[
                    tuple[float, float],
                    str,
                    int,
                    tuple[int, int, int, int],
                ]
                | None
            ) = None
            fallback: list[
                tuple[
                    tuple[int, int, int],
                    tuple[float, float],
                    str,
                    int,
                    tuple[int, int, int, int],
                ]
            ] = []
            for font_size in range(base_size, 6, -1):
                for candidate_index, (xy, anchor) in enumerate(candidates):
                    bbox = canvas.text_bbox(
                        point.y_label,
                        xy,
                        size=font_size,
                        anchor=anchor,
                        max_width=max_width,
                    )
                    padded = _expand_bbox(bbox, 2)
                    score = _label_overlap_score(
                        padded,
                        occupied,
                        bounds=(
                            round(left + 1),
                            round(top + 1),
                            round(right - 1),
                            round(bottom - 1),
                        ),
                    )
                    if score == 0:
                        selected = (xy, anchor, font_size, bbox)
                        break
                    fallback.append(
                        (
                            (score, -font_size, candidate_index),
                            xy,
                            anchor,
                            font_size,
                            bbox,
                        )
                    )
                if selected is not None:
                    break

            if selected is None:
                if not fallback:
                    raise RenderError(f"no value-label placement for point {point.node_id!r}")
                _, xy, anchor, font_size, bbox = min(fallback, key=lambda item: item[0])
            else:
                xy, anchor, font_size, bbox = selected

            label_background = _clip_bbox(
                _expand_bbox(bbox, 2),
                width=canvas.width,
                height=canvas.height,
            )
            canvas.rectangle(point.node_id, label_background, fill=background)
            drawn_bbox = canvas.text(
                point.node_id,
                point.y_label,
                xy,
                size=font_size,
                fill=colour,
                anchor=anchor,
                max_width=max_width,
            )
            assert drawn_bbox is not None
            occupied.append(_expand_bbox(drawn_bbox, 2))


def _value_label_candidates(
    x: float,
    y: float,
    *,
    data_bounds: tuple[float, float, float, float],
    parity: int,
) -> tuple[tuple[tuple[float, float], str], ...]:
    left, top, right, bottom = data_bounds
    above = ((x, y - 9), "mb")
    below = ((x, y + 9), "mt")
    right_of = ((x + 10, y), "lm")
    left_of = ((x - 10, y), "rm")
    above_right = ((x + 7, y - 7), "lb")
    above_left = ((x - 7, y - 7), "rb")
    below_right = ((x + 7, y + 7), "lt")
    below_left = ((x - 7, y + 7), "rt")

    inward = right_of if x <= (left + right) / 2 else left_of
    outward = left_of if inward is right_of else right_of
    if y <= top + (bottom - top) * 0.32:
        primary, secondary = below, above
        diagonal_in = below_right if inward is right_of else below_left
        diagonal_out = below_left if inward is right_of else below_right
    elif y >= top + (bottom - top) * 0.68:
        primary, secondary = above, below
        diagonal_in = above_right if inward is right_of else above_left
        diagonal_out = above_left if inward is right_of else above_right
    elif parity:
        primary, secondary = below, above
        diagonal_in = below_right if inward is right_of else below_left
        diagonal_out = above_left if inward is right_of else above_right
    else:
        primary, secondary = above, below
        diagonal_in = above_right if inward is right_of else above_left
        diagonal_out = below_left if inward is right_of else below_right
    return (
        primary,
        diagonal_in,
        inward,
        secondary,
        diagonal_out,
        outward,
        above_right,
        above_left,
        below_right,
        below_left,
    )


def _expand_bbox(bbox: tuple[int, int, int, int], padding: int) -> tuple[int, int, int, int]:
    return (
        bbox[0] - padding,
        bbox[1] - padding,
        bbox[2] + padding,
        bbox[3] + padding,
    )


def _clip_bbox(
    bbox: tuple[int, int, int, int], *, width: int, height: int
) -> tuple[float, float, float, float]:
    return (
        max(0, bbox[0]),
        max(0, bbox[1]),
        min(width - 1, bbox[2]),
        min(height - 1, bbox[3]),
    )


def _label_overlap_score(
    bbox: tuple[int, int, int, int],
    occupied: Sequence[tuple[int, int, int, int]],
    *,
    bounds: tuple[int, int, int, int],
) -> int:
    left, top, right, bottom = bounds
    overflow = (
        max(0, left - bbox[0])
        + max(0, top - bbox[1])
        + max(0, bbox[2] - right)
        + max(0, bbox[3] - bottom)
    )
    overlap = sum(_bbox_overlap_area(bbox, other) for other in occupied)
    return overflow * 1_000_000 + overlap


def _bbox_overlap_area(first: tuple[int, int, int, int], second: tuple[int, int, int, int]) -> int:
    width = max(0, min(first[2], second[2]) - max(first[0], second[0]))
    height = max(0, min(first[3], second[3]) - max(first[1], second[1]))
    return width * height


def _bar_dimensions(
    canvas_width: int, unique_x_count: int, series_count: int
) -> tuple[float, float]:
    group_width = max(12.0, min(56.0, (canvas_width * 0.58) / max(1, unique_x_count)))
    return group_width, max(3.0, group_width / (max(1, series_count) + 0.4))


def _domain_bound(domain: Mapping[str, Any], axis: str, bound: str) -> Fraction | None:
    direct = domain.get(f"{axis}_{bound}")
    nested = domain.get(axis)
    raw = direct
    if raw is None and isinstance(nested, Mapping):
        raw = nested.get(bound)
    if raw is None:
        return None
    try:
        return parse_number(raw)
    except (TypeError, ValueError, ZeroDivisionError) as exc:
        raise RenderError(f"invalid render_domain {axis}_{bound}: {raw!r}") from exc


def _axis_values(axis: Any) -> list[str]:
    if not isinstance(axis, Mapping):
        return []
    values = axis.get("values") or []
    if not isinstance(values, Sequence) or isinstance(values, (str, bytes)):
        return []
    return [str(value) for value in values if str(value)]


def _axis_label(axis: Any) -> str:
    if isinstance(axis, Mapping):
        return _display_text(axis.get("label"))
    return _display_text(axis)


def _display_text(value: Any) -> str:
    if value is None:
        return ""
    if isinstance(value, Mapping):
        for key in ("text", "label", "title", "name"):
            if value.get(key) is not None:
                return str(value[key])
        return ""
    if isinstance(value, Sequence) and not isinstance(value, (str, bytes)):
        return ", ".join(str(item) for item in value)
    return str(value)


def _plot_type(world: World) -> str:
    return str(world.get("plot_type", "line")).strip().lower() or "line"


def _nondegenerate(low: Fraction, high: Fraction) -> tuple[Fraction, Fraction]:
    if high < low:
        raise RenderError(f"render domain is reversed: {low} > {high}")
    if high == low:
        return low - 1, high + 1
    return low, high


def _format_number(value: Fraction) -> str:
    if value.denominator == 1:
        return str(value.numerator)
    decimal = f"{float(value):.2f}".rstrip("0").rstrip(".")
    return decimal if decimal not in {"-0", ""} else "0"


def _exact_value_label(value: Fraction) -> str:
    """An exact human-readable value: terminating decimal when possible."""
    if value.numerator == 0:
        return "0"
    denominator = value.denominator
    powers_of_two = 0
    powers_of_five = 0
    while denominator % 2 == 0:
        denominator //= 2
        powers_of_two += 1
    while denominator % 5 == 0:
        denominator //= 5
        powers_of_five += 1
    if denominator != 1:
        return canonical_number_str(value)

    decimal_places = max(powers_of_two, powers_of_five)
    scaled = abs(value.numerator)
    scaled *= 2 ** (decimal_places - powers_of_two)
    scaled *= 5 ** (decimal_places - powers_of_five)
    sign = "-" if value.numerator < 0 else ""
    if decimal_places == 0:
        return f"{sign}{scaled}"
    digits = str(scaled).rjust(decimal_places + 1, "0")
    integer = digits[:-decimal_places]
    fractional = digits[-decimal_places:].rstrip("0")
    return f"{sign}{integer}.{fractional}" if fractional else f"{sign}{integer}"


def _dedup(values: Iterable[str]) -> list[str]:
    seen: set[str] = set()
    output: list[str] = []
    for value in values:
        if value not in seen:
            seen.add(value)
            output.append(value)
    return output


def _decimate(values: Sequence[str], maximum: int) -> tuple[str, ...]:
    if len(values) <= maximum:
        return tuple(values)
    indices = {round(index * (len(values) - 1) / (maximum - 1)) for index in range(maximum)}
    return tuple(values[index] for index in sorted(indices))


def _series_colours(family: RendererFamily) -> tuple[str, ...]:
    colours = tuple(
        family.palette[key] for key in sorted(family.palette) if key.startswith("series_")
    )
    if colours:
        return colours
    return (family.palette.get("mark", "#1f77b4"),)


def _pillow_version() -> str:
    import PIL

    return str(PIL.__version__)


_PLOT_TRAIN_FAMILY = RendererFamily(
    name="plot_train_v1",
    kind="plot",
    font_name="DejaVu Sans",
    palette={
        "background": "#FFFFFF",
        "text": "#202020",
        "axis": "#444444",
        "grid": "#D9DEE8",
        "redact": "#151515",
        "mark": "#2563EB",
        "series_0": "#2563EB",
        "series_1": "#EA580C",
        "series_2": "#16A34A",
        "series_3": "#DC2626",
        "series_4": "#7C3AED",
        "series_5": "#A16207",
    },
    layout={"engine": "pillow_v3_exact_labels", "y_ticks": _Y_TICKS},
)
_PLOT_HELDOUT_FAMILY = RendererFamily(
    name="plot_heldout_v1",
    kind="plot",
    font_name="DejaVu Serif",
    palette={
        "background": "#F7F7F0",
        "text": "#17212B",
        "axis": "#38434F",
        "grid": "#D5D2C8",
        "redact": "#303030",
        "mark": "#0F766E",
        "series_0": "#0F766E",
        "series_1": "#BE123C",
        "series_2": "#B7791F",
        "series_3": "#4338CA",
        "series_4": "#A21CAF",
        "series_5": "#475569",
    },
    layout={"engine": "pillow_v3_exact_labels_heldout", "y_ticks": _Y_TICKS},
)

PLOT_FAMILIES: dict[str, RendererFamily] = {
    "plot_train_v1": _PLOT_TRAIN_FAMILY,
    "plot_heldout_v1": _PLOT_HELDOUT_FAMILY,
}


__all__ = ["PLOT_FAMILIES", "PlotRenderer"]