feat(letsplot): implement network-directed (#2895)

## Implementation: `network-directed` - letsplot

Implements the **letsplot** version of `network-directed`.

**File:** `plots/network-directed/implementations/letsplot.py`

**Parent Issue:** #2858

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20608487718)*

---------

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Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

plots/network-directed/implementations/letsplot.py

@@ -0,0 +1,171 @@
+""" pyplots.ai
+network-directed: Directed Network Graph
+Library: letsplot 4.8.2 | Python 3.13.11
+Quality: 91/100 | Created: 2025-12-30
+"""
+
+import os
+import shutil
+
+import numpy as np
+import pandas as pd
+from lets_plot import (
+    LetsPlot,
+    aes,
+    arrow,
+    element_text,
+    geom_point,
+    geom_segment,
+    geom_text,
+    ggplot,
+    ggsize,
+    labs,
+    scale_fill_manual,
+    theme,
+    theme_void,
+    xlim,
+    ylim,
+)
+from lets_plot.export import ggsave
+
+
+LetsPlot.setup_html()
+
+np.random.seed(42)
+
+# Define software package dependency network
+nodes = [
+    {"id": "app", "label": "App", "group": "application"},
+    {"id": "api", "label": "API", "group": "core"},
+    {"id": "auth", "label": "Auth", "group": "core"},
+    {"id": "db", "label": "Database", "group": "core"},
+    {"id": "cache", "label": "Cache", "group": "infrastructure"},
+    {"id": "config", "label": "Config", "group": "utility"},
+    {"id": "logger", "label": "Logger", "group": "utility"},
+    {"id": "utils", "label": "Utils", "group": "utility"},
+    {"id": "http", "label": "HTTP Client", "group": "infrastructure"},
+    {"id": "queue", "label": "Queue", "group": "infrastructure"},
+]
+
+# Directed edges (source depends on target, arrow from source to target)
+edges = [
+    ("app", "api"),
+    ("app", "config"),
+    ("api", "auth"),
+    ("api", "db"),
+    ("api", "cache"),
+    ("api", "logger"),
+    ("auth", "db"),
+    ("auth", "config"),
+    ("auth", "logger"),
+    ("db", "config"),
+    ("db", "logger"),
+    ("cache", "config"),
+    ("cache", "logger"),
+    ("http", "config"),
+    ("http", "logger"),
+    ("queue", "config"),
+    ("queue", "logger"),
+    ("api", "http"),
+    ("api", "queue"),
+    ("utils", "logger"),
+]
+
+# Create node positions using a hierarchical-like layout
+# Manually place nodes in layers for clear dependency visualization
+node_positions = {
+    "app": (0.5, 1.0),
+    "api": (0.5, 0.75),
+    "auth": (0.15, 0.5),
+    "db": (0.5, 0.5),
+    "cache": (0.85, 0.5),
+    "http": (0.05, 0.25),
+    "queue": (0.3, 0.25),
+    "config": (0.55, 0.25),
+    "logger": (0.8, 0.25),
+    "utils": (1.0, 0.75),
+}
+
+# Build node dataframe
+node_df = pd.DataFrame(nodes)
+node_df["x"] = node_df["id"].map(lambda n: node_positions[n][0])
+node_df["y"] = node_df["id"].map(lambda n: node_positions[n][1])
+
+# Color mapping for groups
+group_colors = {
+    "application": "#306998",  # Python Blue
+    "core": "#FFD43B",  # Python Yellow
+    "infrastructure": "#22C55E",  # Green
+    "utility": "#A855F7",  # Purple
+}
+node_df["color"] = node_df["group"].map(group_colors)
+
+# Build edge dataframe with arrow endpoints
+edge_data = []
+for source, target in edges:
+    x0, y0 = node_positions[source]
+    x1, y1 = node_positions[target]
+
+    # Shorten edges to not overlap with nodes
+    dx, dy = x1 - x0, y1 - y0
+    length = np.sqrt(dx**2 + dy**2)
+    if length > 0:
+        # Shrink by node radius on each end
+        shrink = 0.05
+        x0_adj = x0 + (dx / length) * shrink
+        y0_adj = y0 + (dy / length) * shrink
+        x1_adj = x1 - (dx / length) * shrink * 1.8  # More shrink for arrow head
+        y1_adj = y1 - (dy / length) * shrink * 1.8
+    else:
+        x0_adj, y0_adj, x1_adj, y1_adj = x0, y0, x1, y1
+
+    edge_data.append({"x": x0_adj, "y": y0_adj, "xend": x1_adj, "yend": y1_adj})
+
+edge_df = pd.DataFrame(edge_data)
+
+# Create the plot
+plot = (
+    ggplot()
+    # Draw edges with arrows
+    + geom_segment(
+        aes(x="x", y="y", xend="xend", yend="yend"),
+        data=edge_df,
+        color="#64748B",
+        size=1.2,
+        arrow=arrow(length=12, type="closed"),
+        alpha=0.7,
+    )
+    # Draw nodes
+    + geom_point(aes(x="x", y="y", fill="group"), data=node_df, size=22, shape=21, stroke=2.5, color="white")
+    # Add node labels below nodes
+    + geom_text(
+        aes(x="x", y="y", label="label"), data=node_df, size=12, color="#1E293B", fontface="bold", nudge_y=-0.06
+    )
+    # Color scale
+    + scale_fill_manual(values=["#306998", "#FFD43B", "#22C55E", "#A855F7"], name="Module Type")
+    # Theme and styling
+    + theme_void()
+    + theme(
+        plot_title=element_text(size=28, face="bold", hjust=0.5),
+        legend_title=element_text(size=18),
+        legend_text=element_text(size=16),
+        legend_position="right",
+        plot_margin=[60, 80, 80, 60],
+    )
+    + labs(title="network-directed · letsplot · pyplots.ai")
+    + ggsize(1600, 900)
+    + xlim(-0.05, 1.15)
+    + ylim(0.1, 1.1)
+)
+
+# Save as PNG and HTML
+ggsave(plot, "plot.png", scale=3)
+ggsave(plot, "plot.html")
+
+# Move files from lets-plot-images subdirectory to current directory
+if os.path.exists("lets-plot-images/plot.png"):
+    shutil.move("lets-plot-images/plot.png", "plot.png")
+if os.path.exists("lets-plot-images/plot.html"):
+    shutil.move("lets-plot-images/plot.html", "plot.html")
+if os.path.exists("lets-plot-images") and not os.listdir("lets-plot-images"):
+    os.rmdir("lets-plot-images")

plots/network-directed/metadata/letsplot.yaml

@@ -0,0 +1,30 @@
+library: letsplot
+specification_id: network-directed
+created: '2025-12-30T23:57:51Z'
+updated: '2025-12-31T00:05:00Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 20608487718
+issue: 2858
+python_version: 3.13.11
+library_version: 4.8.2
+preview_url: https://storage.googleapis.com/pyplots-images/plots/network-directed/letsplot/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/network-directed/letsplot/plot_thumb.png
+preview_html: https://storage.googleapis.com/pyplots-images/plots/network-directed/letsplot/plot.html
+quality_score: 91
+review:
+  strengths:
+  - Excellent hierarchical layout clearly showing software dependency structure from
+    top (App) to bottom (utilities)
+  - Clean use of lets-plot ggplot2-style grammar with geom_segment arrows and geom_point
+    for nodes
+  - Well-chosen color palette distinguishing four module types (application, core,
+    infrastructure, utility)
+  - Proper edge shortening to prevent arrow overlap with nodes
+  - Correct title format and professional styling with theme_void
+  weaknesses:
+  - Could demonstrate bidirectional edges (curved edges) as mentioned in spec for
+    nodes with mutual connections
+  - File handling code (os, shutil for moving files from lets-plot-images) adds unnecessary
+    complexity
+  - HTML export could leverage lets-plot interactive features like tooltips showing
+    module details