feat: add KYC document renewal alerts, Aadhaar/PAN exceptions, and AML recurring alerts UI; remove old journal AML marking

src/app/clients/shared/kyc-upload-helper.service.ts

@@ -84,6 +84,121 @@ export class KycUploadHelperService {
     );
   }
 
+  /**
+   * Split a stacked front-above-back scan back into its two sides.
+   *
+   * Clients saved before the sides were stored separately carry one merged PNG, so a form that
+   * wants a front image and a back image has nothing to show in the second slot. `mergeFrontBack`
+   * lays the sides on a white canvas with a 20px gap between them, which leaves a band of
+   * completely white rows across the full width — that band is the seam, and it is the only thing
+   * in the file that says where one side ends and the other begins.
+   *
+   * Resolves null when no such seam is found, which is the honest answer for an image that was not
+   * produced by that merge: better to show one scan than to cut a document in half at a guess.
+   */
+  splitFrontBack(blob: Blob): Promise<{ front: Blob; back: Blob } | null> {
+    if (!blob.type.startsWith('image/')) {
+      return Promise.resolve(null);
+    }
+    type Sides = { front: Blob; back: Blob } | null;
+    return this.blobToImage(blob)
+      .then((img): Sides | Promise<Sides> => {
+        const canvas = document.createElement('canvas');
+        canvas.width = img.naturalWidth || img.width;
+        canvas.height = img.naturalHeight || img.height;
+        const ctx = canvas.getContext('2d');
+        if (!ctx || canvas.width === 0 || canvas.height === 0) {
+          return null;
+        }
+        ctx.drawImage(img, 0, 0);
+
+        const seam = this.findWhiteSeam(ctx, canvas.width, canvas.height);
+        if (!seam) {
+          return null;
+        }
+
+        return Promise.all([
+          this.cropToBlob(img, canvas.width, 0, seam.start),
+          this.cropToBlob(img, canvas.width, seam.end, canvas.height - seam.end)
+        ]).then(
+          ([
+            front,
+            back
+          ]): Sides => (front && back ? { front, back } : null)
+        );
+      })
+      .catch((): Sides => null);
+  }
+
+  /**
+   * The tallest run of all-white rows in the middle of the image.
+   *
+   * Confined to the middle half because a scan often has white margins at the top and bottom, and
+   * those are part of the document rather than the join between two of them.
+   */
+  private findWhiteSeam(
+    ctx: CanvasRenderingContext2D,
+    width: number,
+    height: number
+  ): { start: number; end: number } | null {
+    const from = Math.floor(height * 0.25);
+    const to = Math.ceil(height * 0.75);
+    const step = Math.max(1, Math.floor(width / 64)); // sampling is enough to spot a non-white row
+
+    let bestStart = -1;
+    let bestLength = 0;
+    let runStart = -1;
+
+    for (let y = from; y <= to; y++) {
+      let white = y < to;
+      if (white) {
+        const row = ctx.getImageData(0, y, width, 1).data;
+        for (let x = 0; x < width; x += step) {
+          const i = x * 4;
+          if (row[i] < 245 || row[i + 1] < 245 || row[i + 2] < 245) {
+            white = false;
+            break;
+          }
+        }
+      }
+      if (white) {
+        if (runStart < 0) {
+          runStart = y;
+        }
+      } else if (runStart >= 0) {
+        if (y - runStart > bestLength) {
+          bestStart = runStart;
+          bestLength = y - runStart;
+        }
+        runStart = -1;
+      }
+    }
+
+    // The gap the merge inserts is 20px; anything much thinner is white space inside a document.
+    return bestLength >= 12 ? { start: bestStart, end: bestStart + bestLength } : null;
+  }
+
+  private cropToBlob(img: HTMLImageElement, width: number, top: number, height: number): Promise<Blob | null> {
+    if (height <= 0) {
+      return Promise.resolve(null);
+    }
+    const canvas = document.createElement('canvas');
+    canvas.width = width;
+    canvas.height = height;
+    const ctx = canvas.getContext('2d');
+    if (!ctx) {
+      return Promise.resolve(null);
+    }
+    ctx.fillStyle = '#ffffff';
+    ctx.fillRect(0, 0, width, height);
+    ctx.drawImage(img, 0, top, width, height, 0, 0, width, height);
+    return new Promise((resolve) => canvas.toBlob((out) => resolve(out), 'image/png'));
+  }
+
+  private blobToImage(blob: Blob): Promise<HTMLImageElement> {
+    return this.fileToImage(blob as File);
+  }
+
   private fileToImage(file: File): Promise<HTMLImageElement> {
     return new Promise((resolve, reject) => {
       const url = URL.createObjectURL(file);