feat: add pdf generation

Author: srghma

Makefile

@@ -41,3 +41,12 @@ ci: all
 	+@make -B exercises # force make (in case exercise files have been edited directly)
 	if [ -n "$$(git status --porcelain)" ]; then echo 'ERROR: Exercise files are not up-to-date with solutions. `git diff` and `git status` after re-making them:'; git diff; git status; exit 1; fi
 .PHONY: ci
+
+pdf: html
+	@if ! command -v wkhtmltopdf >/dev/null 2>&1; then \
+		echo "wkhtmltopdf not found. Running inside nix-shell..."; \
+		nix-shell -p wkhtmltopdf --run "bash ./generate_pdf.sh"; \
+	else \
+		bash ./generate_pdf.sh; \
+	fi
+.PHONY: pdf

generate_pdf.sh

@@ -0,0 +1,65 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+HTML_DIR="html"
+TOC_FILE="${HTML_DIR}/toc.html"
+
+if [ ! -f "$TOC_FILE" ]; then
+    echo "Error: $TOC_FILE not found! Run 'make html' first."
+    exit 1
+fi
+
+generate_for() {
+    local PREFIX=$1
+    local FILTERED_TOC="${HTML_DIR}/toc_${PREFIX}.html"
+    local OUTPUT_PDF="${PREFIX}.pdf"
+
+    # Capitalize the first letter for the title (Bash 4.0+)
+    local TITLE="Iris Tutorial - ${PREFIX^}"
+
+    echo "--- Building ${OUTPUT_PDF} ---"
+
+    # 1. Generate the filtered TOC
+    # This awk script passes through everything outside `<div id="toc">`.
+    # Inside the TOC, it checks each `<h2>` to see if the link belongs to
+    # the current prefix (e.g., "solutions"). If so, it keeps printing until
+    # the next `<h2>` tells it to stop.
+    awk -v prefix="$PREFIX" '
+    BEGIN { printing = 1; in_toc = 0; }
+    /<div id="toc">/ { in_toc = 1; print; next; }
+    /<\/div>/ && in_toc { in_toc = 0; print; next; }
+    /<h2/ && in_toc {
+        if ($0 ~ "href=\"" prefix "\\.") printing = 1;
+        else printing = 0;
+    }
+    { if (!in_toc || printing) print; }
+    ' "$TOC_FILE" > "$FILTERED_TOC"
+
+    # 2. Extract the ordered list of HTML filenames for this prefix.
+    # By only looking at lines with '<h2', we cleanly grab the top-level files.
+    local FILES
+    FILES=$(grep '<h2' "$TOC_FILE" | grep -oE 'href="'"${PREFIX}"'\.[^"]*\.html"' | cut -d'"' -f2 | awk '!x[$0]++')
+
+    # 3. Assemble inputs (starting with the filtered TOC)
+    local INPUTS=("$FILTERED_TOC")
+    for f in $FILES; do
+        INPUTS+=("${HTML_DIR}/$f")
+    done
+
+    echo "Combining ${#INPUTS[@]} HTML files into ${OUTPUT_PDF}..."
+
+    # 4. Generate the PDF
+    wkhtmltopdf \
+        --enable-local-file-access \
+        --javascript-delay 500 \
+        --title "$TITLE" \
+        --footer-center "[page] / [topage]" \
+        "${INPUTS[@]}" \
+        "$OUTPUT_PDF"
+
+    echo "+++ Successfully generated ${OUTPUT_PDF} +++"
+    echo ""
+}
+
+generate_for "exercises"
+generate_for "solutions"