From 2fd86a66fcc2665e5672cc5862e24b3782ee7504 Mon Sep 17 00:00:00 2001
From: Raymond Hill <rhill@raymondhill.net>
Date: Mon, 9 Sep 2019 14:06:23 -0400
Subject: [PATCH] Add json-prune.js scriptlet

The scriptlet will trap calls to JSON.parse, and
if the result of the parsing is an Object, it
will remove specified properties from the result
before returning to the caller.

Usage:

    ##+js(json-prune, arg1, [arg2])

Where:

- arg1: a list of space-separated properties to remove

- arg2: optional, a list of space-separated properties
        which must be all present for the pruning to
        occur

Example:

    ##+js(json-prune, enabled, adpath config)

A property in a list of properties can be a chain
of properties, example: adpath.url.first
---
 assets/resources/scriptlets.js | 55 ++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/assets/resources/scriptlets.js b/assets/resources/scriptlets.js
index 55a44c83e..ce9297f15 100644
--- a/assets/resources/scriptlets.js
+++ b/assets/resources/scriptlets.js
@@ -236,6 +236,61 @@
 })();
 
 
+/// json-prune.js
+(function() {
+    const log = console.log.bind(console);
+    const rawPrunePaths = '{{1}}';
+    const rawNeedlePaths = '{{2}}';
+    const prunePaths = rawPrunePaths !== '{{1}}' && rawPrunePaths !== ''
+        ? rawPrunePaths.split(/ +/)
+        : [];
+    const needlePaths = rawNeedlePaths !== '{{2}}' && rawNeedlePaths !== ''
+        ? rawNeedlePaths.split(/ +/)
+        : [];
+    const findOwner = function(root, path) {
+        let owner = root;
+        let chain = path;
+        for (;;) {
+            if ( owner instanceof Object === false ) { return; }
+            const pos = chain.indexOf('.');
+            if ( pos === -1 ) {
+                return owner.hasOwnProperty(chain)
+                    ? [ owner, chain ]
+                    : undefined;
+            }
+            const prop = chain.slice(0, pos);
+            if ( owner.hasOwnProperty(prop) === false ) { return; }
+            owner = owner[prop];
+            chain = chain.slice(pos + 1);
+        }
+    };
+    const mustProcess = function(root) {
+        for ( const needlePath of needlePaths ) {
+            const details = findOwner(root, needlePath);
+            if ( details === undefined ) { return false; }
+        }
+        return true;
+    };
+    JSON.parse = new Proxy(JSON.parse, {
+        apply: function() {
+            const r = Reflect.apply(...arguments);
+            if ( prunePaths.length === 0 ) {
+                log(location.hostname, r);
+                return r;
+            }
+            if ( mustProcess(r) === false ) { return r; }
+            for ( const path of prunePaths ) {
+                const details = findOwner(r, path);
+                if ( details !== undefined ) {
+                    delete details[0][details[1]];
+                }
+            }
+            return r;
+        },
+    });
+})();
+
+
 // Imported from:
 // https://github.com/NanoAdblocker/NanoFilters/blob/1f3be7211bb0809c5106996f52564bf10c4525f7/NanoFiltersSource/NanoResources.txt#L126
 //