﻿
CREATE   FUNCTION [dbo].[json_diffObjectArrays] (@SourceJSON NVARCHAR(MAX), @TargetJSON NVARCHAR(MAX), @uniquekey varchar(50) )
/**
Summary: >
  This function 'diffs' a source JSON document with a target JSON document and produces an
  analysis of which properties are missing in either the source or target, or the values
  of these properties that are different. It reports on the properties and values for 
  both source and target as well as the path that references that scalar value. The 
  path reference to the object's parent is exposed in the result to enable a query to
  reference the value of any other object in the parent that is needed. 
Author: Phil Factor
Date: 06/07/2020
Revised:
	- mod: Added the parent reference to the difference report
	- Date: 09/07/2020
Database: PhilsRoutines
Examples:
   - SELECT * FROM dbo.Compare_JsonObject(@TheSourceJSON, @TheTargetJSON)
       WHERE SideIndicator <> '==';
   - SELECT *, Json_Value(@TheSourceJSON,TheParent+'.name')
       FROM dbo.Compare_JsonObject(@TheSourceJSON, @TheTargetJSON)
       WHERE SideIndicator <> '==';
Returns: >
  SideIndicator:  ( == equal, <- not in target, ->  not in source, <> not equal
  ThePath:   the JSON path used by the SQL JSON functions 
  TheKey:  the key field without the path
  TheSourceValue: the value IN the SOURCE JSON document
  TheTargetValue: the value IN the TARGET JSON document
 
**/
RETURNS @returntable TABLE
  (
	  [equal] [bit],
	  [action] smallint,
	  [uid] varchar(100),
	  [diff] nvarchar(max)
  )
AS
  BEGIN

	  DECLARE @objects TABLE (
		[uid] varchar(100),
		[json] NVARCHAR(MAX)
	  )
	  INSERT INTO @objects ([uid], [json])
		SELECT JSON_VALUE(j.[Value], '$.' + @uniquekey), [value]
			FROM OpenJson(@TargetJSON) as j
			WHERE type IN (4,5);

	  DECLARE @intermediate TABLE
	  (
		  [equal] [bit],
		  [SideIndicator] CHAR(2),		--	== means equal, <- means not in target, -> means not in source, <> means not equal
		  [UID] varchar(100),
		  [parent]  VARCHAR(2000),	--	the parent object
		  [path] VARCHAR(2000),		--	the JSON path used by the SQL JSON functions 
		  [key] VARCHAR(255),			--	the key field without the path
		  [SourceValue] NVARCHAR(max), --	the value IN the SOURCE JSON document
		  [TargetValue] NVARCHAR(max)	--	the value IN the TARGET JSON document
	  )
	  INSERT INTO @intermediate
		SELECT * FROM [dbo].[json_compareObjectArrays](@SourceJSON, @TargetJSON, @uniquekey);
    
	 WITH d as(
		SELECT
			[UID]
			, [total] = SUM(1)
			, [LEFT] = SUM(IIF([sideindicator] = '<-',1,0))
			, [RIGHT] = SUM(IIF([sideindicator] = '->',1,0))
			, [inequal] = SUM(IIF(i.[equal] = 1,0,1))
		FROM @intermediate as i
		GROUP BY [UID]
	 )
	 INSERT INTO @returntable
		SELECT
			[equal] = IIF([inequal] = 0, 1 ,0)
			, CASE WHEN [total] = [RIGHT] THEN 2
				   WHEN [total] = [LEFT] THEN -1
				  WHEN [inequal] > 0 THEN 1
				  ELSE 0 END	
			, ISNULL(o.[uid], d.[UID])
			, [j] = IIF([inequal] = 0, '{}' ,	--( SELECT [key] = im.[theKey], [val] = im.[TheTargetValue] FROM @intermediate as im WHERE im.[UID] = d.[UID] AND im.equal  = 0 FOR JSON PATH, WITHOUT_ARRAY_WRAPPER  )
							o.[json]
			)
		FROM d
			FULL OUTER JOIN @objects as o ON d.[UID] = o.[uid]
		
		DECLARE @uid varchar(100), @key varchar(100);

		DECLARE im_cursor CURSOR FOR 
		SELECT [uid], [key]  
			FROM @intermediate
			WHERE [SideIndicator] in ('==');

		OPEN im_cursor  
		FETCH NEXT FROM im_cursor INTO @uid, @key;

		WHILE @@FETCH_STATUS = 0  
		BEGIN  
			  UPDATE o 
				SET o.[diff] = JSON_MODIFY(o.[diff], '$.' + @key, null)
				FROM @returntable as o
				WHERE [uid] = @uid;

			  FETCH NEXT FROM im_cursor INTO @uid, @key;
		END 

		CLOSE im_cursor ;
		DEALLOCATE im_cursor;

    RETURN;
  END;