From ddf73c23a4b727fc69c269d3131292913a7d7b6b Mon Sep 17 00:00:00 2001
From: Pete Schaffner <peteschaffner@icloud.com>
Date: Tue, 12 May 2020 11:22:13 +0200
Subject: [PATCH] Add ability to remove items from a section (#75)

---
 Sources/Publish/API/PublishingStep.swift      | 20 ++++++++++++
 Sources/Publish/API/Section.swift             | 31 +++++++++++++------
 .../Tests/ContentMutationTests.swift          | 16 ++++++++++
 3 files changed, 57 insertions(+), 10 deletions(-)

diff --git a/Sources/Publish/API/PublishingStep.swift b/Sources/Publish/API/PublishingStep.swift
index abb22b41..0742e780 100644
--- a/Sources/Publish/API/PublishingStep.swift
+++ b/Sources/Publish/API/PublishingStep.swift
@@ -134,6 +134,26 @@ public extension PublishingStep {
             try MarkdownFileHandler().addMarkdownFiles(in: folder, to: &context)
         }
     }
+    
+    /// Remove all items matching a predicate, optionally within a specific section.
+    /// - parameter section: Any specific section to remove all items within.
+    /// - parameter predicate: Any predicate to filter the items using.
+    static func removeAllItems(
+        in section: Site.SectionID? = nil,
+        matching predicate: Predicate<Item<Site>> = .any
+    ) -> Self {
+        let nameSuffix = section.map { " in '\($0)'" } ?? ""
+
+        return step(named: "Remove items" + nameSuffix) { context in
+            if let section = section {
+                context.sections[section].removeItems(matching: predicate)
+            } else {
+                for section in context.sections.ids {
+                    context.sections[section].removeItems(matching: predicate)
+                }
+            }
+        }
+    }
 
     /// Mutate all items matching a predicate, optionally within a specific section.
     /// - parameter section: Any specific section to mutate all items within.
diff --git a/Sources/Publish/API/Section.swift b/Sources/Publish/API/Section.swift
index 530da9bd..75e6c76d 100644
--- a/Sources/Publish/API/Section.swift
+++ b/Sources/Publish/API/Section.swift
@@ -94,21 +94,19 @@ public extension Section {
             return item
         }
     }
+    
+    /// Remove all items within this section matching a given predicate.
+    /// - Parameter predicate: Any predicate to filter the items based on.
+    mutating func removeItems(matching predicate: Predicate<Item<Site>> = .any) {
+        items.removeAll(where: predicate.matches)
+        rebuildIndexes()
+    }
 
     /// Sort all items within this section using a closure.
     /// - Parameter sorter: The closure to use to sort the items.
     mutating func sortItems(by sorter: (Item<Site>, Item<Site>) throws -> Bool) rethrows {
         try items.sort(by: sorter)
-        itemIndexesByPath = [:]
-        itemIndexesByTag = [:]
-
-        for (index, item) in items.enumerated() {
-            itemIndexesByPath[item.relativePath] = index
-
-            for tag in item.tags {
-                itemIndexesByTag[tag, default: []].insert(index)
-            }
-        }
+        rebuildIndexes()
     }
 }
 
@@ -169,4 +167,17 @@ private extension Section {
 
         lastItemModificationDate = newDate
     }
+    
+    mutating func rebuildIndexes() {
+        itemIndexesByPath = [:]
+        itemIndexesByTag = [:]
+
+        for (index, item) in items.enumerated() {
+            itemIndexesByPath[item.relativePath] = index
+
+            for tag in item.tags {
+                itemIndexesByTag[tag, default: []].insert(index)
+            }
+        }
+    }
 }
diff --git a/Tests/PublishTests/Tests/ContentMutationTests.swift b/Tests/PublishTests/Tests/ContentMutationTests.swift
index 6273b929..a6575a5d 100644
--- a/Tests/PublishTests/Tests/ContentMutationTests.swift
+++ b/Tests/PublishTests/Tests/ContentMutationTests.swift
@@ -32,6 +32,21 @@ final class ContentMutationTests: PublishTestCase {
         XCTAssertEqual(site.sections[.one].items.first?.body.html, "<div>Plot!</div>")
     }
 
+    func testRemovingItemsMatchingPredicate() throws {
+        let items = [
+            Item.stub(withPath: "a").setting(\.tags, to: ["one"]),
+            Item.stub(withPath: "b").setting(\.tags, to: ["one", "two"])
+        ]
+
+        let site = try publishWebsite(using: [
+            .addItems(in: items),
+            .removeAllItems(matching: \.tags ~= "two")
+        ])
+
+        XCTAssertEqual(site.sections[.one].items, [items[0]])
+        XCTAssertNil(site.sections[.one].item(at: "b"), "Item indexes not updated")
+    }
+
     func testMutatingAllSections() throws {
         let site = try publishWebsite(using: [
             .step(named: "Set section titles") { context in
@@ -280,6 +295,7 @@ extension ContentMutationTests {
         [
             ("testAddingItemUsingClosureAPI", testAddingItemUsingClosureAPI),
             ("testAddingItemUsingPlotHierarchy", testAddingItemUsingPlotHierarchy),
+            ("testRemovingItemsMatchingPredicate", testRemovingItemsMatchingPredicate),
             ("testMutatingAllSections", testMutatingAllSections),
             ("testMutatingAllItems", testMutatingAllItems),
             ("testMutatingItemsInSection", testMutatingItemsInSection),