From 61eb967c354ee10ad39168f790eb6c989fdef0c6 Mon Sep 17 00:00:00 2001
From: Alsey Coleman Miller <alseycmiller@gmail.com>
Date: Mon, 21 Aug 2023 01:24:59 -0400
Subject: [PATCH] Add `BSONDocument.init(predicate:)`

---
 Sources/MongoDBModel/FetchRequest.swift  | 10 ----
 Sources/MongoDBModel/MongoDatabase.swift |  4 +-
 Sources/MongoDBModel/Predicate.swift     | 61 ++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 12 deletions(-)
 create mode 100644 Sources/MongoDBModel/Predicate.swift

diff --git a/Sources/MongoDBModel/FetchRequest.swift b/Sources/MongoDBModel/FetchRequest.swift
index a665319..89a11d0 100644
--- a/Sources/MongoDBModel/FetchRequest.swift
+++ b/Sources/MongoDBModel/FetchRequest.swift
@@ -7,18 +7,8 @@
 
 import Foundation
 import CoreModel
-import Predicate
 import MongoSwift
 
-public extension BSONDocument {
-    
-    init(filter predicate: Predicate) {
-        self.init()
-        // TODO:
-        assertionFailure("Not implemented")
-    }
-}
-
 public extension BSONDocument {
     
     init(sort sortDescriptors: [FetchRequest.SortDescriptor]) {
diff --git a/Sources/MongoDBModel/MongoDatabase.swift b/Sources/MongoDBModel/MongoDatabase.swift
index 472befa..ca17326 100644
--- a/Sources/MongoDBModel/MongoDatabase.swift
+++ b/Sources/MongoDBModel/MongoDatabase.swift
@@ -108,7 +108,7 @@ internal extension MongoDatabase {
     ) async throws -> UInt {
         let entityName = fetchRequest.entity
         let collection = self.collection(entityName, options: options)
-        let filter = fetchRequest.predicate.map { BSONDocument(filter: $0) } ?? [:]
+        let filter = fetchRequest.predicate.flatMap { BSONDocument(predicate: $0) } ?? [:]
         let options = CountDocumentsOptions(fetchRequest: fetchRequest)
         let count = try await collection.countDocuments(filter, options: options)
         return UInt(count)
@@ -173,7 +173,7 @@ internal extension MongoDatabase {
     ) async throws -> [BSONDocument] {
         let entityName = fetchRequest.entity
         let collection = self.collection(entityName, options: options)
-        let filter = fetchRequest.predicate.map { BSONDocument(filter: $0) } ?? [:]
+        let filter = fetchRequest.predicate.flatMap { BSONDocument(predicate: $0) } ?? [:]
         let options = FindOptions(fetchRequest: fetchRequest)
         let stream = try await collection.find(filter, options: options)
         var results = [BSONDocument]()
diff --git a/Sources/MongoDBModel/Predicate.swift b/Sources/MongoDBModel/Predicate.swift
new file mode 100644
index 0000000..1c32915
--- /dev/null
+++ b/Sources/MongoDBModel/Predicate.swift
@@ -0,0 +1,61 @@
+//
+//  Predicate.swift
+//  
+//
+//  Created by Alsey Coleman Miller on 8/21/23.
+//
+
+import Foundation
+import CoreModel
+import Predicate
+import MongoSwift
+
+public extension BSONDocument {
+    
+    init?(predicate: Predicate) {
+        switch predicate {
+        case .comparison(let comparison):
+            self.init(predicate: comparison)
+        case .compound(let compound):
+            self.init(predicate: compound)
+        case .value:
+            return nil
+        }
+    }
+}
+
+public extension BSONDocument {
+    
+    init?(predicate: Compound) {
+        guard predicate.type != .not else {
+            // { field: { $not: { <operator-expression> } } }
+            return nil
+        }
+        var array = [BSONDocument]()
+        array.reserveCapacity(predicate.subpredicates.count)
+        for subpredicate in predicate.subpredicates {
+            guard let document = BSONDocument(predicate: subpredicate) else {
+                return nil
+            }
+            array.append(document)
+        }
+        // { $and: [ { <expression1> }, { <expression2> } , ... , { <expressionN> } ] }
+        // { $or: [ { <expression1> }, { <expression2> }, ... , { <expressionN> } ] }
+        self = [LogicalQueryOperator(predicate: predicate.type).rawValue: .array(array.map { .document($0) })]
+    }
+}
+
+public extension BSONDocument {
+    
+    init?(predicate: Comparison) {
+        // { <field>: { $eq: <value> } }
+        return nil
+    }
+}
+
+public extension BSON {
+    
+    init?(predicate: Expression) {
+        return nil
+    }
+}