From 86f07b8e7c61e2433fbec1945330d288d265109d Mon Sep 17 00:00:00 2001
From: Ivan Zinovyev <zinovyev-ivan@yandex.ru>
Date: Sun, 4 Nov 2018 08:28:50 +0300
Subject: [PATCH] Add AccurateCellHeightCalculator

---
 Sources/AccurateCellHeightCalculator.swift | 45 ++++++++++++++++++++++
 TableKit.xcodeproj/project.pbxproj         |  4 ++
 2 files changed, 49 insertions(+)
 create mode 100644 Sources/AccurateCellHeightCalculator.swift

diff --git a/Sources/AccurateCellHeightCalculator.swift b/Sources/AccurateCellHeightCalculator.swift
new file mode 100644
index 0000000..e266790
--- /dev/null
+++ b/Sources/AccurateCellHeightCalculator.swift
@@ -0,0 +1,45 @@
+import UIKit
+
+class AccurateCellHeightCalculator: RowHeightCalculator {
+
+    private(set) weak var tableView: UITableView?
+    private var prototypes = [String: UITableViewCell]()
+    private var cachedHeights = [Int: CGFloat]()
+
+    public init(tableView: UITableView?) {
+        self.tableView = tableView
+    }
+
+    open func height(forRow row: Row, at indexPath: IndexPath) -> CGFloat {
+
+        guard let tableView = tableView else { return 0 }
+
+        let hash = row.hashValue ^ Int(tableView.bounds.size.width).hashValue
+
+        if let height = cachedHeights[hash] {
+            return height
+        }
+
+        var prototypeCell = prototypes[row.reuseIdentifier]
+        if prototypeCell == nil {
+
+            prototypeCell = tableView.dequeueReusableCell(withIdentifier: row.reuseIdentifier)
+            prototypes[row.reuseIdentifier] = prototypeCell
+        }
+
+        guard let cell = prototypeCell else { return  0 }
+        let height = row.height(for: cell)
+
+        cachedHeights[hash] = height
+
+        return height
+    }
+
+    open func estimatedHeight(forRow row: Row, at indexPath: IndexPath) -> CGFloat {
+        return height(forRow: row, at: indexPath)
+    }
+
+    open func invalidate() {
+        cachedHeights.removeAll()
+    }
+}
diff --git a/TableKit.xcodeproj/project.pbxproj b/TableKit.xcodeproj/project.pbxproj
index 9afc02f..b30ee04 100644
--- a/TableKit.xcodeproj/project.pbxproj
+++ b/TableKit.xcodeproj/project.pbxproj
@@ -7,6 +7,7 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		320C5280218EB9A7004EAD1C /* AccurateCellHeightCalculator.swift in Sources */ = {isa = PBXBuildFile; fileRef = 320C527F218EB9A7004EAD1C /* AccurateCellHeightCalculator.swift */; };
 		50CF6E6B1D6704FE004746FF /* TableCellRegisterer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 50CF6E6A1D6704FE004746FF /* TableCellRegisterer.swift */; };
 		50E858581DB153F500A9AA55 /* TableKit.swift in Sources */ = {isa = PBXBuildFile; fileRef = 50E858571DB153F500A9AA55 /* TableKit.swift */; };
 		DA9EA7AF1D0EC2C90021F650 /* ConfigurableCell.swift in Sources */ = {isa = PBXBuildFile; fileRef = DA9EA7A61D0EC2C90021F650 /* ConfigurableCell.swift */; };
@@ -32,6 +33,7 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		320C527F218EB9A7004EAD1C /* AccurateCellHeightCalculator.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AccurateCellHeightCalculator.swift; sourceTree = "<group>"; };
 		50CF6E6A1D6704FE004746FF /* TableCellRegisterer.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = TableCellRegisterer.swift; sourceTree = "<group>"; };
 		50E858571DB153F500A9AA55 /* TableKit.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = TableKit.swift; sourceTree = "<group>"; };
 		DA9EA7561D0B679A0021F650 /* TableKit.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = TableKit.framework; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -100,6 +102,7 @@
 				DA9EA7A71D0EC2C90021F650 /* TablePrototypeCellHeightCalculator.swift */,
 				DA9EA7A61D0EC2C90021F650 /* ConfigurableCell.swift */,
 				DA9EA7A81D0EC2C90021F650 /* Operators.swift */,
+				320C527F218EB9A7004EAD1C /* AccurateCellHeightCalculator.swift */,
 			);
 			path = Sources;
 			sourceTree = "<group>";
@@ -233,6 +236,7 @@
 				50CF6E6B1D6704FE004746FF /* TableCellRegisterer.swift in Sources */,
 				DA9EA7AF1D0EC2C90021F650 /* ConfigurableCell.swift in Sources */,
 				DA9EA7B31D0EC2C90021F650 /* TableDirector.swift in Sources */,
+				320C5280218EB9A7004EAD1C /* AccurateCellHeightCalculator.swift in Sources */,
 				DA9EA7B71D0EC2C90021F650 /* TableSection.swift in Sources */,
 				DA9EA7B01D0EC2C90021F650 /* TablePrototypeCellHeightCalculator.swift in Sources */,
 				DA9EA7B51D0EC2C90021F650 /* TableRowAction.swift in Sources */,