smart redaction (#6195)

Co-authored-by: James Brunton <[email protected]>

app/common/src/main/java/stirling/software/SPDF/pdf/parser/PageColumnLayout.java

@@ -0,0 +1,142 @@
+package stirling.software.SPDF.pdf.parser;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Detects whether a page is one- or two-column from per-line bounding boxes, and classifies an
+ * X-span into the column it belongs to. Detection is a midpoint vote at {@code pageWidth / 2}.
+ *
+ * <p>Capped at two columns by design — sufficient for the redaction target set (single-column
+ * documents and IEEE-style two-column papers). 3+ column layouts (newspapers, magazines) and
+ * off-centre gutters (asymmetric two-column) would need a histogram or clustering approach to
+ * detect the actual gutter X. (future work)
+ *
+ * <p>Coordinates are PDFTextStripper screen space (top-left origin, Y increases downward).
+ */
+public final class PageColumnLayout {
+
+    /**
+     * Slack when checking "crosses a gutter" so single-pixel overshoots don't mark a line as
+     * spanning.
+     */
+    public static final float SPAN_SLACK_PT = 2f;
+
+    /**
+     * Slack on each side of the page midpoint inside which a line is considered "spanning"
+     * (covering both columns) rather than belonging to one side.
+     */
+    private static final float MIDPOINT_SLACK_PT = 30f;
+
+    /**
+     * Minimum line width (points) for a line to count toward the two-column tally. Avoids false
+     * positives where right-aligned dates, page numbers, or short "Link" fragments next to a
+     * heading look like a second column when they're really just inline metadata.
+     */
+    private static final float MIN_COLUMN_LINE_WIDTH_PT = 100f;
+
+    /**
+     * Minimum number of clearly leftish AND clearly rightish lines (each of width &ge; {@link
+     * #MIN_COLUMN_LINE_WIDTH_PT}) required to call the page two-column. Anything below this falls
+     * back to single-column.
+     */
+    private static final int MIN_SIDE_LINES = 3;
+
+    private final List<float[]> columns;
+    private final List<float[]> gutters;
+
+    private PageColumnLayout(List<float[]> columns, List<float[]> gutters) {
+        this.columns = columns;
+        this.gutters = gutters;
+    }
+
+    /**
+     * Determines column layout from per-line bounding boxes ({@code [x1, _, x2, _]}). Counts lines
+     * whose X-midpoint sits clearly left of, or clearly right of, the page midpoint (with {@link
+     * #MIDPOINT_SLACK_PT} slack each side). If both sides have at least {@link #MIN_SIDE_LINES}
+     * lines, the page is treated as two-column with the gutter at the page midpoint. Otherwise it's
+     * single-column.
+     *
+     * <p>Cross-column lines must already be split: callers should feed boxes from a line extractor
+     * that splits same-Y glyphs at large X gaps (see {@code AllTextLineExtractor}). Without that
+     * split, IEEE-style aligned-baseline 2-column PDFs produce one wide merged box per row and the
+     * side tallies all end up classified as "spanning", falling to single-column.
+     */
+    public static PageColumnLayout fromLineBoxes(List<float[]> lineBoxes, float pageWidth) {
+        if (lineBoxes == null || lineBoxes.isEmpty()) {
+            return new PageColumnLayout(List.of(new float[] {0f, pageWidth}), List.of());
+        }
+        float pageMid = pageWidth / 2f;
+        int left = 0, right = 0;
+        for (float[] lb : lineBoxes) {
+            if (lb == null || lb.length < 3) continue;
+            float width = lb[2] - lb[0];
+            // Skip narrow lines — dates, page numbers, "Link" labels next to a heading should
+            // not, on their own, make a single-column doc look two-column.
+            if (width < MIN_COLUMN_LINE_WIDTH_PT) continue;
+            float mid = (lb[0] + lb[2]) * 0.5f;
+            if (mid < pageMid - MIDPOINT_SLACK_PT) left++;
+            else if (mid > pageMid + MIDPOINT_SLACK_PT) right++;
+        }
+        if (left < MIN_SIDE_LINES || right < MIN_SIDE_LINES) {
+            return new PageColumnLayout(List.of(new float[] {0f, pageWidth}), List.of());
+        }
+        float gutterL = pageMid - MIDPOINT_SLACK_PT;
+        float gutterR = pageMid + MIDPOINT_SLACK_PT;
+        return new PageColumnLayout(
+                List.of(new float[] {0f, gutterL}, new float[] {gutterR, pageWidth}),
+                List.of(new float[] {gutterL, gutterR}));
+    }
+
+    /** All columns, left-to-right, as {@code [leftX, rightX]} pairs. Never empty. */
+    public List<float[]> columns() {
+        return columns;
+    }
+
+    /** Gutters between columns, left-to-right, as {@code [leftX, rightX]} pairs. */
+    public List<float[]> gutters() {
+        return gutters;
+    }
+
+    public int columnCount() {
+        return columns.size();
+    }
+
+    /**
+     * Returns the column index containing the X-midpoint of {@code [x1, x2]}, falling back to the
+     * closest column if the midpoint sits inside a gutter.
+     */
+    public int columnOf(float x1, float x2) {
+        float mid = (x1 + x2) * 0.5f;
+        int best = 0;
+        float bestDist = Float.MAX_VALUE;
+        for (int i = 0; i < columns.size(); i++) {
+            float[] c = columns.get(i);
+            if (mid >= c[0] && mid <= c[1]) return i;
+            float dist = mid < c[0] ? c[0] - mid : mid - c[1];
+            if (dist < bestDist) {
+                bestDist = dist;
+                best = i;
+            }
+        }
+        return best;
+    }
+
+    /**
+     * Returns every column index whose X-range overlaps {@code [x1, x2]} with at least {@link
+     * #SPAN_SLACK_PT} of intrusion. A normal in-column line returns one index; a line crossing a
+     * gutter returns two or more.
+     */
+    public int[] columnsCrossing(float x1, float x2) {
+        List<Integer> hits = new ArrayList<>();
+        for (int i = 0; i < columns.size(); i++) {
+            float[] c = columns.get(i);
+            float overlap = Math.min(x2, c[1]) - Math.max(x1, c[0]);
+            if (overlap > SPAN_SLACK_PT) hits.add(i);
+        }
+        if (hits.isEmpty()) hits.add(columnOf(x1, x2));
+        int[] out = new int[hits.size()];
+        for (int i = 0; i < hits.size(); i++) out[i] = hits.get(i);
+        return out;
+    }
+}

app/common/src/main/java/stirling/software/SPDF/pdf/parser/PageImageLocator.java

@@ -0,0 +1,133 @@
+package stirling.software.SPDF.pdf.parser;
+
+import java.awt.geom.Point2D;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.pdfbox.contentstream.PDFGraphicsStreamEngine;
+import org.apache.pdfbox.cos.COSName;
+import org.apache.pdfbox.pdmodel.PDPage;
+import org.apache.pdfbox.pdmodel.graphics.image.PDImage;
+import org.apache.pdfbox.util.Matrix;
+
+/**
+ * PDFGraphicsStreamEngine that intercepts {@code drawImage} calls and records each image's bounding
+ * box in PDF user-space (origin bottom-left, Y up) by transforming the unit square through the
+ * current transformation matrix (CTM).
+ *
+ * <p>Usage:
+ *
+ * <pre>{@code
+ * PageImageLocator locator = new PageImageLocator(page, pageIndex);
+ * locator.processPage(page);
+ * List<ImageBox> boxes = locator.getImageBoxes();
+ * }</pre>
+ *
+ * <p>Each {@link ImageBox} carries the 0-based page index and the axis-aligned bounding box {@code
+ * (x1, y1, x2, y2)} in PDF user-space coordinates.
+ */
+public final class PageImageLocator extends PDFGraphicsStreamEngine {
+
+    /**
+     * Bounding box of a raster or vector image found on a PDF page.
+     *
+     * @param pageIndex 0-based page index
+     * @param x1 left edge in PDF user-space (origin bottom-left)
+     * @param y1 bottom edge in PDF user-space
+     * @param x2 right edge
+     * @param y2 top edge
+     */
+    public record ImageBox(int pageIndex, float x1, float y1, float x2, float y2) {}
+
+    private final int pageIndex;
+    private final List<ImageBox> imageBoxes = new ArrayList<>();
+    private final Point2D.Float currentPoint = new Point2D.Float();
+
+    /**
+     * @param page the PDPage to process
+     * @param pageIndex 0-based index of this page in the document (stored on each returned {@link
+     *     ImageBox})
+     */
+    public PageImageLocator(PDPage page, int pageIndex) {
+        super(page);
+        this.pageIndex = pageIndex;
+    }
+
+    /** Returns all image bounding boxes collected during {@link #processPage}. */
+    public List<ImageBox> getImageBoxes() {
+        return imageBoxes;
+    }
+
+    @Override
+    public void drawImage(PDImage pdImage) throws IOException {
+        Matrix ctm = getGraphicsState().getCurrentTransformationMatrix();
+        // An image occupies the unit square (0,0)→(1,1) in image space.
+        // Transform all four corners through the CTM to get the page-space bounding box.
+        float a = ctm.getScaleX();
+        float b = ctm.getShearY();
+        float c = ctm.getShearX();
+        float d = ctm.getScaleY();
+        float e = ctm.getTranslateX();
+        float f = ctm.getTranslateY();
+        float[] xs = {e, a + e, c + e, a + c + e};
+        float[] ys = {f, b + f, d + f, b + d + f};
+        float x1 = Float.MAX_VALUE, y1 = Float.MAX_VALUE;
+        float x2 = -Float.MAX_VALUE, y2 = -Float.MAX_VALUE;
+        for (float x : xs) {
+            x1 = Math.min(x1, x);
+            x2 = Math.max(x2, x);
+        }
+        for (float y : ys) {
+            y1 = Math.min(y1, y);
+            y2 = Math.max(y2, y);
+        }
+        imageBoxes.add(new ImageBox(pageIndex, x1, y1, x2, y2));
+    }
+
+    // ---------- required abstract methods (no-op for path operations) ----------
+
+    @Override
+    public void appendRectangle(Point2D p0, Point2D p1, Point2D p2, Point2D p3) {}
+
+    @Override
+    public void clip(int windingRule) {}
+
+    @Override
+    public void moveTo(float x, float y) {
+        currentPoint.setLocation(x, y);
+    }
+
+    @Override
+    public void lineTo(float x, float y) {
+        currentPoint.setLocation(x, y);
+    }
+
+    @Override
+    public void curveTo(float x1, float y1, float x2, float y2, float x3, float y3) {
+        currentPoint.setLocation(x3, y3);
+    }
+
+    @Override
+    public Point2D getCurrentPoint() {
+        return currentPoint;
+    }
+
+    @Override
+    public void closePath() {}
+
+    @Override
+    public void endPath() {}
+
+    @Override
+    public void strokePath() {}
+
+    @Override
+    public void fillPath(int windingRule) {}
+
+    @Override
+    public void fillAndStrokePath(int windingRule) {}
+
+    @Override
+    public void shadingFill(COSName shadingName) {}
+}

app/common/src/main/java/stirling/software/common/util/propertyeditor/JsonListPropertyEditor.java

@@ -0,0 +1,48 @@
+package stirling.software.common.util.propertyeditor;
+
+import java.beans.PropertyEditorSupport;
+import java.util.ArrayList;
+import java.util.List;
+
+import lombok.extern.slf4j.Slf4j;
+
+import tools.jackson.core.type.TypeReference;
+import tools.jackson.databind.DeserializationFeature;
+import tools.jackson.databind.ObjectMapper;
+import tools.jackson.databind.json.JsonMapper;
+
+/**
+ * Binds a multipart form value containing a JSON array into a typed {@code List<T>}. Used for
+ * endpoints that accept structured list parameters via {@code @ModelAttribute} — the form field
+ * carries the full JSON array as its value and the editor parses it once.
+ */
+@Slf4j
+public class JsonListPropertyEditor<T> extends PropertyEditorSupport {
+
+    private static final ObjectMapper OBJECT_MAPPER =
+            JsonMapper.builder()
+                    .enable(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY)
+                    .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
+                    .build();
+
+    private final TypeReference<? extends List<T>> typeRef;
+
+    public JsonListPropertyEditor(TypeReference<? extends List<T>> typeRef) {
+        this.typeRef = typeRef;
+    }
+
+    @Override
+    public void setAsText(String text) throws IllegalArgumentException {
+        if (text == null || text.trim().isEmpty()) {
+            setValue(new ArrayList<T>());
+            return;
+        }
+        try {
+            setValue(OBJECT_MAPPER.readValue(text, typeRef));
+        } catch (Exception e) {
+            log.error("Failed to parse JSON list value", e);
+            throw new IllegalArgumentException(
+                    "Expected a JSON array but could not parse: " + e.getMessage());
+        }
+    }
+}

app/common/src/main/java/stirling/software/common/util/propertyeditor/JsonObjectPropertyEditor.java

@@ -0,0 +1,41 @@
+package stirling.software.common.util.propertyeditor;
+
+import java.beans.PropertyEditorSupport;
+
+import lombok.extern.slf4j.Slf4j;
+
+import tools.jackson.databind.DeserializationFeature;
+import tools.jackson.databind.ObjectMapper;
+import tools.jackson.databind.json.JsonMapper;
+
+/**
+ * Binds a multipart form value containing a JSON object into a typed {@code T}. Companion to {@link
+ * JsonListPropertyEditor} for single-object nested fields on {@code @ModelAttribute} endpoints.
+ */
+@Slf4j
+public class JsonObjectPropertyEditor<T> extends PropertyEditorSupport {
+
+    private static final ObjectMapper OBJECT_MAPPER =
+            JsonMapper.builder().disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES).build();
+
+    private final Class<T> type;
+
+    public JsonObjectPropertyEditor(Class<T> type) {
+        this.type = type;
+    }
+
+    @Override
+    public void setAsText(String text) throws IllegalArgumentException {
+        if (text == null || text.trim().isEmpty()) {
+            setValue(null);
+            return;
+        }
+        try {
+            setValue(OBJECT_MAPPER.readValue(text, type));
+        } catch (Exception e) {
+            log.error("Failed to parse JSON object value", e);
+            throw new IllegalArgumentException(
+                    "Expected a JSON object but could not parse: " + e.getMessage());
+        }
+    }
+}

app/common/src/main/java/stirling/software/common/util/propertyeditor/StringToArrayListPropertyEditor.java

@@ -1,53 +0,0 @@
-package stirling.software.common.util.propertyeditor;
-
-import java.beans.PropertyEditorSupport;
-import java.util.ArrayList;
-import java.util.List;
-
-import lombok.extern.slf4j.Slf4j;
-
-import tools.jackson.databind.DeserializationFeature;
-import tools.jackson.databind.JavaType;
-import tools.jackson.databind.ObjectMapper;
-import tools.jackson.databind.json.JsonMapper;
-
-/**
- * Spring property editor that decodes a JSON string into a typed {@link ArrayList}. Used to bind
- * complex list parameters (e.g. {@code List<RedactionArea>}, {@code List<EditTextOperation>}) from
- * multipart form fields, where Spring's default binding cannot deserialize a JSON array.
- */
-@Slf4j
-public class StringToArrayListPropertyEditor<T> extends PropertyEditorSupport {
-
-    private final ObjectMapper objectMapper =
-            JsonMapper.builder()
-                    .enable(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY)
-                    .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
-                    .build();
-
-    private final Class<T> elementType;
-
-    public StringToArrayListPropertyEditor(Class<T> elementType) {
-        this.elementType = elementType;
-    }
-
-    @Override
-    public void setAsText(String text) throws IllegalArgumentException {
-        if (text == null || text.trim().isEmpty()) {
-            setValue(new ArrayList<>());
-            return;
-        }
-        try {
-            JavaType listType =
-                    objectMapper
-                            .getTypeFactory()
-                            .constructCollectionType(ArrayList.class, elementType);
-            List<T> list = objectMapper.readValue(text, listType);
-            setValue(list);
-        } catch (Exception e) {
-            log.error("Exception while converting {}", e);
-            throw new IllegalArgumentException(
-                    "Failed to convert java.lang.String to java.util.List");
-        }
-    }
-}