package JsonParser
import public Json
import SeqWorker
import LinkedList

/**
	Provides functionality to parse JSON (JasSObjectNotation).
	It is a minimal format to save space and allow for better compression.

	A Json object is a collection of properties that have one letter as name
	and an int or a list of json objects as value.
	Examples: 
		x1y2 // Two component vector
		a[x1y2]b[x2y1] // Two lists of vectors

	To parse toplevel properties use the #parse function.
	To parse a list of json objects use the #parseList function
*/

constant numbermap = "-0123456789"
constant lettermap = "abcdefghijklmnopqrstuvwxyz"


public enum TokenType
	NONE
	LETTER
	NUMBER
	OPEN_ARRAY
	CLOSE_ARRAY


public class JsonParser
	BigString bigInput = null
	int currentPosition = 0
	int propStartPosition = 0
	int squareBracketLvl = 0
	TokenType lastType = TokenType.NONE
	string currentToken = null
	Json output = new Json()
	LinkedList<BigSubString> outputList = null
	BigSubString propName = null
	BigSubString propVal = null

	function setInput(BigString bs)
		this.bigInput = bs
		currentPosition = 0
		propStartPosition = 0
		squareBracketLvl = 0
		lastType = TokenType.NONE
		currentToken = null

	/** Parses a list of objects.
		Example: [x1_x2_x3] -> parsed: x1, x2, x3	*/
	function parseList(PayloadCallback finalCallback)
		if outputList != null
			destroy outputList
		outputList = new LinkedList<BigSubString>()
		if bigInput.getLength() <= 2
			Log.debug("skip empty list")
			finalCallback.doStep()
		else
			doSeq() cb ->
				var continue = true
				if currentPosition < bigInput.getLength()
					parseListSeq()
				else
					continue = false
					Log.debug("parsed list")
					finalCallback.doStep()
				return continue


	private function parseListSeq()
		currentToken = bigInput.getString(currentPosition, 1)
		switch currentToken
			case JSON_OPEN_ARRAY.token
				squareBracketLvl++
				if squareBracketLvl == 1
					propStartPosition = currentPosition+1
			case JSON_CLOSE_ARRAY.token
				squareBracketLvl--
				if squareBracketLvl == 0
					let bss = new BigSubString(bigInput, propStartPosition, currentPosition-propStartPosition)
					outputList.add(bss)
					propStartPosition = currentPosition+1
			case JSON_SIGN_COMMA.token
				if squareBracketLvl == 1
					let bss = new BigSubString(bigInput, propStartPosition, currentPosition-propStartPosition)
					outputList.add(bss)
					propStartPosition = currentPosition+1
			default
		
		currentPosition++

	/** Parses a toplevel json 
		Example: a1b2c[a1b2] -> parsed: a = 1, b = 2, c = [a1b2]	*/
	function parse(PayloadCallback callback)
		if bigInput == null or bigInput.getLength() <= 0
			Log.debug("skip empty input")
			callback.doStep()
			return
		bigInput.debugPrint()
		output.reset()
		doSeq() cb ->
			var continue = true
			if currentPosition < bigInput.getLength()
				parseSeq()
			else
				continue = false
				if propStartPosition < currentPosition
					propVal = new BigSubString(bigInput, propStartPosition, currentPosition-propStartPosition)
					output.addProperty(new Property(propName, propVal))
				callback.doStep()
			return continue

	private function parseSeq()
		currentToken = bigInput.getString(currentPosition, 1)
		switch currentToken
			case JSON_OPEN_ARRAY.token
				squareBracketLvl++
				if squareBracketLvl == 1
					propStartPosition = currentPosition
				lastType = TokenType.OPEN_ARRAY
			case JSON_CLOSE_ARRAY.token
				squareBracketLvl--
				if squareBracketLvl == 0
					propVal = new BigSubString(bigInput, propStartPosition, currentPosition-propStartPosition+1)
					output.addProperty(new Property(propName, propVal))
					propStartPosition = currentPosition+1
				lastType = TokenType.CLOSE_ARRAY
			default
				if squareBracketLvl == 0
					if lettermap.contains(currentToken)
						onLetter()
					else if numbermap.contains(currentToken)
						onNumber()
		
		currentPosition++

	private function onNumber()
		switch lastType
			case LETTER
				propStartPosition = currentPosition
			default
		lastType = TokenType.NUMBER

	private function onLetter()
		switch lastType
			case NONE
				propName = new BigSubString(bigInput, currentPosition, 1)
				propStartPosition = currentPosition+1
			case NUMBER
				propVal = new BigSubString(bigInput, propStartPosition, currentPosition-propStartPosition)
				output.addProperty(new Property(propName, propVal))
				propName = new BigSubString(bigInput, currentPosition, 1)
				propStartPosition = currentPosition+1
			case CLOSE_ARRAY
				propName = new BigSubString(bigInput, currentPosition, 1)
				propStartPosition = currentPosition+1
			default
		lastType = TokenType.LETTER


	ondestroy
		if bigInput != null
			destroy bigInput
		if output != null
			destroy output
		if outputList != null
			for bss from outputList.staticItr()
				destroy bss
			destroy outputList