Resubmit Supervised user web restrictions content provider

components/web_restriction/java/src/org/chromium/components/webrestriction/WebRestrictionsContentProvider.java

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.components.webrestriction;
+
+import android.content.ContentProvider;
+import android.content.ContentValues;
+import android.content.Context;
+import android.content.UriMatcher;
+import android.content.pm.ProviderInfo;
+import android.database.AbstractCursor;
+import android.database.Cursor;
+import android.net.Uri;
+import android.util.Pair;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Abstract content provider for providing web restrictions, i.e. for providing a filter for URLs so
+ * that they can be blocked or permitted, and a means of requesting permission for new URLs. It
+ * provides two (virtual) tables; an 'authorized' table listing the the status of every URL, and a
+ * 'requested' table containing the requests for access to new URLs. The 'authorized' table is read
+ * only and the 'requested' table is write only.
+ */
+public abstract class WebRestrictionsContentProvider extends ContentProvider {
+    public static final int BLOCKED = 0;
+    public static final int PROCEED = 1;
+    private static final int WEB_RESTRICTIONS = 1;
+    private static final int AUTHORIZED = 2;
+    private static final int REQUESTED = 3;
+
+    private final Pattern mSelectionPattern;
+    private UriMatcher mContentUriMatcher;
+    private Uri mContentUri;
+
+    protected WebRestrictionsContentProvider() {
+        // Pattern to extract the URL from the selection.
+        // Matches patterns of the form "url = '<url>'" with arbitrary spacing around the "=" etc.
+        mSelectionPattern = Pattern.compile("\\s*url\\s*=\\s*'([^']*)'");
+    }
+
+    @Override
+    public boolean onCreate() {
+        return true;
+    }
+
+    @Override
+    public void attachInfo(Context context, ProviderInfo info) {
+        super.attachInfo(context, info);
+        mContentUri = new Uri.Builder().scheme("content").authority(info.authority).build();
+        mContentUriMatcher = new UriMatcher(WEB_RESTRICTIONS);
+        mContentUriMatcher.addURI(info.authority, "authorized", AUTHORIZED);
+        mContentUriMatcher.addURI(info.authority, "requested", REQUESTED);
+    }
+
+    @Override
+    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
+            String sortOrder) {
+        // Check that this is the a query on the 'authorized' table
+        // TODO(aberent): Provide useful queries on the 'requested' table.
+        if (mContentUriMatcher.match(uri) != AUTHORIZED) return null;
+        // If the selection is of the right form get the url we are querying.
+        Matcher matcher = mSelectionPattern.matcher(selection);
+        if (!matcher.find()) return null;
+        final String url = matcher.group(1);
+        final Pair<Boolean, String> result = shouldProceed(url);
+
+        return new AbstractCursor() {
+
+            @Override
+            public int getCount() {
+                return 1;
+            }
+
+            @Override
+            public String[] getColumnNames() {
+                return new String[] {"Should Proceed", "Error message"};
+            }
+
+            @Override
+            public String getString(int column) {
+                if (column == 1) return result.second;
+                return null;
+            }
+
+            @Override
+            public short getShort(int column) {
+                return 0;
+            }
+
+            @Override
+            public int getInt(int column) {
+                if (column == 0) return result.first ? PROCEED : BLOCKED;
+                return 0;
+            }
+
+            @Override
+            public long getLong(int column) {
+                return 0;
+            }
+
+            @Override
+            public float getFloat(int column) {
+                return 0;
+            }
+
+            @Override
+            public double getDouble(int column) {
+                return 0;
+            }
+
+            @Override
+            public boolean isNull(int column) {
+                return false;
+            }
+        };
+    }
+
+    @Override
+    public String getType(Uri uri) {
+        // Abused to return whether we can insert
+        if (mContentUriMatcher.match(uri) != REQUESTED) return null;
+        return canInsert() ? "text/plain" : null;
+    }
+
+    @Override
+    public Uri insert(Uri uri, ContentValues values) {
+        if (mContentUriMatcher.match(uri) != REQUESTED) return null;
+        String url = values.getAsString("url");
+        if (requestInsert(url)) {
+            // TODO(aberent): If we ever make the 'requested' table readable then we might want to
+            // change this to a more conventional content URI (with a row number).
+            return uri.buildUpon().appendPath(url).build();
+        } else {
+            return null;
+        }
+    }
+
+    @Override
+    public int delete(Uri uri, String selection, String[] selectionArgs) {
+        return 0;
+    }
+
+    @Override
+    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
+        return 0;
+    }
+
+    /**
+     * @param url the URL that is wanted.
+     * @return a pair containing the Result and the HTML Error Message. result is true if safe to
+     *         proceed, false otherwise. error message is only meaningful if result is false, a null
+     *         error message means use application default.
+     */
+    protected abstract Pair<Boolean, String> shouldProceed(final String url);
+
+    /**
+     * @return whether the content provider allows insertions.
+     */
+    protected abstract boolean canInsert();
+
+    /**
+     * Start a request that a URL should be permitted
+     *
+     * @param url the URL that is wanted.
+     */
+    protected abstract boolean requestInsert(final String url);
+
+    /**
+     * Call to tell observers that the filter has changed.
+     */
+    protected void onFilterChanged() {
+        getContext().getContentResolver().notifyChange(
+                mContentUri.buildUpon().appendPath("authorized").build(), null);
+    }
+}