Add Json to Postgres WithProps

src/Postgres/Library.fs

@@ -1,5 +1,9 @@
 namespace BitBadger.Documents.Postgres
 
+open System.IO
+open System.Text
+open Npgsql.FSharp
+
 /// <summary>The type of index to generate for the document</summary>
 [<Struct>]
 type DocumentIndex =
@@ -302,3 +306,60 @@ module Results =
     [<CompiledName "ToExists">]
     let toExists (row: RowReader) =
         row.bool "it"
+
+    /// <summary>Extract a JSON document, specifying the field in which the document is found</summary>
+    /// <param name="field">The field name containing the JSON document</param>
+    /// <param name="row">A row reader set to the row with the document to be extracted</param>
+    /// <returns>The JSON from the given field (an empty object if no field exists)</returns>
+    [<CompiledName "JsonFromDocument">]
+    let jsonFromDocument field (row: RowReader) =
+        row.stringOrNone field |> Option.defaultValue "{}"
+
+    /// <summary>Extract a JSON document</summary>
+    /// <param name="row">A row reader set to the row with the document to be extracted</param>
+    /// <returns>The JSON from the row (an empty object if no field exists)</returns>
+    [<CompiledName "JsonFromData">]
+    let jsonFromData row =
+        jsonFromDocument "data" row
+
+    /// <summary>Create a JSON array of items for the results of a query</summary>
+    /// <param name="mapFunc">The mapping function to extract JSON from the query's results</param>
+    /// <param name="sqlProps">The query from which JSON should be extracted</param>
+    /// <returns>A JSON array as a string; no results will produce an empty array (<c>"[]"</c>)</returns>
+    [<CompiledName "FSharpToJsonArray">]
+    let toJsonArray (mapFunc: RowReader -> string) sqlProps =
+        let output = StringBuilder("[")
+        sqlProps
+        |> Sql.iter (fun it ->
+            if output.Length > 2 then ignore (output.Append ",")
+            mapFunc it |> output.Append |> ignore)
+        output.Append("]").ToString()
+
+    /// <summary>Create a JSON array of items for the results of a query</summary>
+    /// <param name="mapFunc">The mapping function to extract JSON from the query's results</param>
+    /// <param name="sqlProps">The query from which JSON should be extracted</param>
+    /// <returns>A JSON array as a string; no results will produce an empty array (<c>"[]"</c>)</returns>
+    let ToJsonArray(mapFunc: System.Func<RowReader, string>, sqlProps) =
+        toJsonArray mapFunc.Invoke sqlProps
+
+    /// <summary>Write a JSON array of items for the results of a query to the given <c>StreamWriter</c></summary>
+    /// <param name="writer">The StreamWriter to which results should be written</param>
+    /// <param name="mapFunc">The mapping function to extract JSON from the query's results</param>
+    /// <param name="sqlProps">The query from which JSON should be extracted</param>
+    [<CompiledName "FSharpWriteJsonArray">]
+    let writeJsonArray (writer: StreamWriter) (mapFunc: RowReader -> string) sqlProps =
+        writer.Write "["
+        let mutable isFirst = true
+        sqlProps
+        |> Sql.iter (fun it ->
+            if isFirst then isFirst <- false else writer.Write ","
+            mapFunc it |> writer.Write)
+        writer.Write "]"
+
+    /// <summary>Write a JSON array of items for the results of a query to the given <c>StreamWriter</c></summary>
+    /// <param name="writer">The StreamWriter to which results should be written</param>
+    /// <param name="mapFunc">The mapping function to extract JSON from the query's results</param>
+    /// <param name="sqlProps">The query from which JSON should be extracted</param>
+    let WriteJsonArray(writer, mapFunc: System.Func<RowReader, string>, sqlProps) =
+        writeJsonArray writer mapFunc.Invoke sqlProps
+