xpath.ahk

/*
	Title: XPath Quick Reference

	License:
		- Version 3.14 <http://www.autohotkey.net/~polyethene/#xpath>
		- Dedicated to the public domain (CC0 1.0) <http://creativecommons.org/publicdomain/zero/1.0/>
*/

/*
	Function: xpath
		Selects nodes and attributes from a standard xpath expression.

	Parameters:
		doc - an xml object returned by xpath_load()
		step - a valid XPath 2.0 expression
		set - (optional) text content to replace the current selection

	Returns:
		The XML source of the selection.
		If the content was set to be modified the previous value will be returned.

	Remarks:
		Since multiple return values are seperated with a comma,
		any found within the text content will be entity escaped as &#44;.
		To get or set the text content of a node use the text function,
		e.g. /root/node/text(); this behaviour is always assumed within predicates.
		For performance reasons count() and last() do not update with the creation of new nodes
		so you may need to alter the results accordingly.
*/
xpath(ByRef doc, step, set = "") {
	static sc, scb = "" ; use EOT (\x04) as delimiter
	
	If step contains %scb% ; i.e. illegal character
		Return
	sid := scb . &doc . ":" ; should be unique identifier for current XML object
	If (InStr(step, "select:") == 1) { ; for quick selection
		stsl = 1
		StringTrimLeft, step, step, 7
	}
	If (InStr(step, "/") == 1)
		str = 1 ; root selected
	Else {
		StringGetPos, p, sc, %sid% ; retrieve previous path
		If ErrorLevel = 1
			t = /
		Else StringMid, t, sc, p += StrLen(sid) + 1, InStr(sc, scb, "", p + 2) - p
		step = %t%/%step%
	}
	
	; normalize path e.g. /root/node/../child/. becomes /root/child:
	step := RegExReplace(step, "(?<=^|/)(?:[^\[/@]+/\.{2}|\.)(?:/|$)|^.+(?=//)")
	
	If (str == 1 or stsl == 1) { ; if not relative path and no select:
		; remove last node and trailing attributes and functions:
		xpr := RegExReplace(step, (str == 1 and stsl != 1 ? "/(?:\w+:)?\w+(?:\[[^\]]*])?" : "")
			. "(?:/@.*?|/\w+\(\))*$")
		StringReplace, xpr, xpr, [-1], [1], All ; -1 become just 1
		StringReplace, xpr, xpr, [+1], [last()], All ; +1 becomes last()
		StringGetPos, p, sc, %sid%
		If ErrorLevel = 1
			sc = %sc%%sid%%xpr%%scb% ; add record or update as necessary:
		Else sc := SubStr(sc, 1, p += StrLen(sid)) . xpr . SubStr(sc, InStr(sc, scb, "", p))
	}
	
	; for unions call each operand seperately and join results:
	If (InStr(step, "|")) {
		StringSplit, s, step, |, `n`t  `r
		Loop, %s0%
			res .= xpath(doc, s%A_Index%, set) . ","
		Return, SubStr(res, 1, -1)
	}
	Else If (InStr(step, "//") == 1) { ; for wildcard selectors use regex searching mode:
		StringTrimLeft, step, step, 2
		re = 1
		rew = 1
		xp = /(?:(?:\w+:)?\w+)*/
	}
	
	NumPut(160, doc, 0, "UChar") ; unmask variable
	
	; resolve xpath components to: absolute node path, attributes and predicates (if any)
	Loop, Parse, step, /
	{
		s = %A_LoopField%
		If (InStr(s, "*") == 1) ; regex mode for wildcards
		{
			re = 1
			s := "(?:\w+:)?\w+" . SubStr(s, 2)
		}
		Else If (InStr(s, "@") == 1) { ; if current step is attribute:
			StringTrimLeft, atr, s, 1
			Continue
		}
		StringGetPos, p, s, [ ; look for predicate opening [...]
		If ErrorLevel = 0
		{
			If s contains [+1],[-1] ; for child nodes record creation instructions in a list
			{
				If A_Index = 2 ; root node creation
				{
					StringLeft, t, s, p
					t = <%t%/:: ></%t%/>
					If (InStr(s, "+1")) {
						If doc =
							doc = .
						doc = %doc%%t%
					}
					Else doc = .%t%%doc%
					StringLeft, s, s, InStr(s, "[") - 1
				}
				Else {
					nw = %nw%%s%
					Continue
				}
			}
			Else { ; i.e. for conditional predicates
				
				If (InStr(s, "last()")) { ; finding last node
					StringLeft, t, s, p
					t := "<" . SubStr(xp, 2) . t . "/:: "
					If re ; with regex:
					{
						os = 0
						Loop
							If (!os := RegExMatch(doc, t, "", 1 + os)) {
								t = %A_Index%
								Break
							}
						t--
					}
					Else { ; otherwise using StringReplace
						StringReplace, doc, doc, %t%, %t%, UseErrorLevel
						t = %ErrorLevel%
					}
					If (RegExMatch(s, "i)last\(\)\s*\-\s*(\d+)", a)) ; i.e. [last() - 2]
						StringReplace, s, s, %a%, % t - a1
					Else StringReplace, s, s, last(), %t%
				}
				
				; concat. the predicate to the list against the current absolute path:
				ax = %ax%%xp%%s%
				StringLeft, s, s, p
			}
		}
		Else If (InStr(s, "()")) { ; if step is function, add to list
			fn = %fn%+%s% ; use + prefix to prevent overlapping naming conflicts
			Continue
		}
		; finally, if step is not any of the above, assume it's the name of a child node
		xp = %xp%%s%/ ; ... and add to list, forming the absolute path
	}
	
	If (xp == "" or xp == "/") ; i.e. error cases
		Return
	
	; remove initial root selector (/) as this is how the parser works by default:
	StringTrimLeft, xp, xp, 1
	StringTrimRight, ax, ax, 1
	
	StringTrimRight, nw, nw, 1
	
	ct = 0 ; counter
	os = 0 ; offset for main loop starts at zero
	Loop {
		; find offset of next element, and its closing tag offset:
		If re
			os := RegExMatch(doc, "<" . xp . ":: ", "", 1 + os)
				, osx := RegExMatch(doc, "</" . xp . ">", rem, os) + StrLen(rem)
		Else {
			StringGetPos, osx, doc, </%xp%>, , os := InStr(doc, "<" . xp . ":: ", true, 1 + os)
			osx += 4 + StrLen(xp)
		}
		If os = 0 ; stop looping when no more tags are found
			Break
		
		; predicate parser:
		If ax !=
		{
			sk = 0
			Loop, Parse, ax, ] ; for each predicate
			{
				; split components to: (1) path, (2) selector, (3) operator, (4) quotation char, (5) operand
				If (!RegExMatch(A_LoopField, "/?(.*?)\[(.+?)(?:\s*([<>!=]{1,2})\s*(['""])?(.+)(?(4)\4))?\s*$", a))
					Continue
				a1 = %a1%/
				If re
					RegExMatch(rem, "(?<=^</)" . a1, a1)
				
				If a2 is integer ; i.e. match only certain index
				{
					StringGetPos, t, a1, /, R2
					StringMid, t, a1, 1, t + 1
					t := InStr(SubStr(doc, 1, os), "<" . t . ":: ", true, 0)
					; extract parent node:
					StringMid, sub, doc, t, InStr(doc, ">", "", os) - t
					xpf := "<" . a1 . ":: "
					; get index of current element within parent node:
					StringReplace, sub, sub, %xpf%, %xpf%, UseErrorLevel
					If a2 != %ErrorLevel%
						sk = 1
					Continue
				}
				
				StringReplace, xp, xp, /, /, UseErrorLevel
				t = %ErrorLevel%
				StringReplace, a1, a1, /, /, UseErrorLevel
				
				 ; extract result for deep analysis
				If t = %ErrorLevel% ; i.e. /root/node[child='test']
					StringMid, sub, doc, os, osx - os
				Else StringMid, sub, doc
					 	, t := InStr(SubStr(doc, 1, os), "<" . a1 . ":: ", true, 0)
					 	, InStr(doc, "</" . a1 . ">", true, t) + 1
				
				If a2 = position()
					sub = %i%
				Else If (InStr(a2, "@") == 1) ; when selector is an attribute:
				 RegExMatch(SubStr(sub, 1, InStr(sub, ">"))
						, a3 == "" ? "\b" . SubStr(a2, 2) . "=([""'])[^\1]*?\1"
						: "\b(?<=" . SubStr(a2, 2) . "=([""']))[^\1]+?(?=\1)", sub)
				Else ; otherwise child node:
				{
					If a2 = . ; if selector is current node don't append to path:
						a2 = /
					Else a2 = %a2%/
					StringMid, sub, sub
						, t := InStr(sub, ">", "", InStr(sub, "<" . a1 . a2 . ":: ", true) + 1) + 1
						, InStr(sub, "</" . a1 . a2 . ">", true) - t
				}
				
				; dynamic mini expression evaluator:
				sk += !(a3 == "" ? (sub != "")
					: a3 == "=" ? sub == a5
					: a3 == "!=" ? sub != a5
					: a3 == ">" ? sub > a5
					: a3 == ">=" ? sub >= a5
					: a3 == "<" ? sub < a5
					: a3 == "<=" ? sub <= a5)
			}
			If sk != 0 ; if conditions were not met for this result, skip it
				Continue
		}
		
		If nw != ; for node creation
		{
			If re
				nwp := SubStr(rem, 3, -1)
			Else nwp = %xp%
			Loop, Parse, nw, ]
			{
				StringLeft, nwn, A_LoopField, InStr(A_LoopField, "[") - 1
				nwn = %nwn%/
				nwt = <%nwp%%nwn%:: ></%nwp%%nwn%>
				If (t := InStr(A_LoopField, "-1")
					? InStr(doc, ">", "", InStr(doc, "<" . nwp . ":: ", true, os) + 1) + 1
					: InStr(doc, "</" . nwp . ">", true, os))
					os := t
				StringLen, osx, nwt
				osx += os
				doc := SubStr(doc, 1, os - 1) . nwt . SubStr(doc, os)
				nwp = %nwp%%nwn%
			}
			StringLen, t, nwp
			If (InStr(fn, "+text()") and atr == "")
				os += t + 5, osx -= t + 3
		}
		
		If atr !=
		{
			; extract attribute offsets, with surrounding declaration if text() is not used:
			If (t := RegExMatch(SubStr(doc, os, InStr(doc, ">", "", os) - os), InStr(fn, "+text()")
				? "(?<=\b" . atr . "=([""']))[^\1]*?(?=\1)"
				: "\b" . atr . "=([""'])[^\1]*?\1", rem))
				os += t - 1, osx := os + StrLen(rem)
			Else { ; create attribute
				os := InStr(doc, ">", "", os + 1)
					, doc := SubStr(doc, 1, os - 1) . " " . atr . "=""""" . SubStr(doc, os)
					, osx := ++os + StrLen(atr) + 3
				If (InStr(fn, "+text()"))
					osx := os += StrLen(atr) + 2
			}
		}
		Else If (InStr(fn, "+text()") and nw == "") ; for text content:
			os := InStr(doc, ">", "", os) + 1, osx := InStr(doc, re ? rem : "</" . xp . ">", true, os)
		
		If InStr(fn, "+index-of()") ; get index rather than content
			sub = %A_Index% 
		Else StringMid, sub, doc, os, osx - os ; extract result
		
		If (InStr(fn, "+count()")) ; increment counter if count() function is used
			ct++
		Else res = %res%%sub%, ; ... and concat to list
		
		If (set != "" or InStr(fn, "+remove()")) ; modify or remove...
			setb = %setb%%os%.%osx%| ; mark for modification
	}
	
	If setb !=
	{
		If (InStr(set, "node:") == 1) {
			set := SubStr(xpath(doc, SubStr(set, 6) . "/rawsrc()"), 2)
			StringReplace, set, set, <, <%xp%, All
			StringReplace, set, set, <%xp%/, </%xp%, All
			NumPut(160, doc, 0, "UChar")
		}
		StringTrimRight, setb, setb, 1
		Loop, Parse, setb, |
		{
			StringSplit, setp, A_LoopField, .
			StringLen, t, xp
			If (InStr(fn, "+append()"))
				setp2 := setp1 := setp2 - t - 3
			Else If (InStr(fn, "+prepend()"))
				setp2 := setp1 := InStr(doc, ">", "", setp1) + 2
			doc := SubStr(doc, 1, setp1 - 1) . set . SubStr(doc, setp2) ; dissect then insert new value
		}
	}
	
	If (InStr(fn, "+count()"))
		res = %ct%, ; trailing char since SubStr is used below
	
	nsid := scb . &doc . ":" ; update sid as necessary
	If nsid != %sid%
		StringReplace, sc, sc, %sid%, %nsid%
	
	NumPut(0, doc, 0, "UChar") ; remask variable to prevent external editing
	StringTrimRight, res, res, 1
	If (InStr(fn, "+rawsrc()")) {
		StringTrimLeft, t, xpr, 1
		StringReplace, res, res, <%t%/, <, All
		StringReplace, res, res, </%t%, <, All
		StringReplace, res, res, `,, `,%scb%, All
		Return, scb . res
	}
	; remove trailing comma and absolute paths from result before returning:
	Return, RegExReplace(res, "S)(?<=<)(\/)?(?:(\w+)\/)+(?(1)|:: )", "$1$2")
}

/*
	Function: xpath_save
		Saves an XML document to file or returns the source.

	Parameters:
		doc - an xml object returned by xpath_load()
		src - (optional) a path to a file where the XML document should be saved;
			if the file already exists it will be replaced

	Returns:
		False if there was an error in saving the document, true otherwise.
		If the src parameter is left blank the source code of the document is returned instead.
*/
xpath_save(ByRef doc, src = "") {
	xml := RegExReplace(SubStr(doc, 2), "S)(?<=<)(\/)?(?:(\w+)\/)+(?(1)|:: )", "$1$2") ; remove metadata
	xml := RegExReplace(xml, "<([\w:]+)([^>]*)><\/\1>", "<$1$2 />") ; fuse empty nodes
	;xml := RegExReplace(xml, " (?=(?:\w+:)?\w+=['""])") ; remove prepending whitespace on attributes
	xml := RegExReplace(xml, "^\s+|\s+$") ; remove start and leading whitespace
	StringReplace, xml, xml, `r, , All ; normalize linefeeds:
	StringReplace, xml, xml, `n, `r`n, All
	sp := "  "
	StringLen, sl, sp
	s =
	VarSetCapacity(sxml, StrLen(xml) * 1.1)
	Loop, Parse, xml, <, `n`t 	 `r
	{
		If A_LoopField =
			Continue
		If (sb := InStr(A_LoopField, "/") == 1)
			StringTrimRight, s, s, sl
		sxml = %sxml%`n%s%<%A_LoopField%
		If sb
			StringTrimRight, s, s, sl
		If (InStr(A_LoopField, "?") != 1 and InStr(A_LoopField, "!") != 1
			and !InStr(A_LoopField, "/>"))
			s .= sp
	}
	StringTrimLeft, sxml, sxml, 1
	sxml := RegExReplace(sxml, "(\n(?:" . sp . ")*<((?:\w+:)?\w+\b)[^<]+?)\n(?:"
		. sp . ")*</\2>", "$1</$2>")
	If InStr(xml, "<?xml") != 1 ; add processor instruction if there isn't any:
		xml = <?xml version="1.0" encoding="iso-8859-1"?>`r`n%xml%
	If src = ; if save path not specified return the XML document:
		Return, sxml
	FileDelete, %src% ; delete existing file
	FileAppend, %sxml%, %src% ; create new one
	Return, ErrorLevel ; return errors, if any
}

/*
	Function: xpath_load
		Loads an XML document.

	Parameters:
		doc - a reference to the loaded XML file as a variable, to be used in other functions
		src - (optional) the document to load, this can be a file name or a string,
			if omitted the first paramter is used as the source

	Returns:
		False if there was an error in loading the document, true otherwise.
*/
xpath_load(ByRef doc, src = "") {
	If src = ; if source is empty assume the out variable is the one to be loaded
		src = %doc%
	Else If FileExist(src) ; otherwise read from file (if it exists)
		FileRead, src, %src%
	If src not contains <,>
		Return, false
	; combined expressions slightly improve performance:
	src := RegExReplace(src, "<((?:\w+:)?\w+\b)([^>]*)\/\s*>", "<$1$2></$1>") ; defuse nodes
		, VarSetCapacity(doc, VarSetCapacity(xml, StrLen(src) * 1.5) * 1.1) ; pre-allocate enough space
	Loop, Parse, src, < ; for each opening tag:
	{
		If (A_Index == 2 and InStr(A_LoopField, "?xml") == 1)
			Continue
		Else If (InStr(A_LoopField, "?") == 1) ; ignore all other processor instructions
			xml = %xml%<%A_LoopField%
		Else If (InStr(A_LoopField, "![CDATA[") == 1) { ; escape entities in CDATA sections
			cdata := SubStr(A_LoopField, 9, -3)
			StringReplace, cdata, cdata, ", &quot;, All
			StringReplace, cdata, cdata, &, &amp;, All
			StringReplace, cdata, cdata, ', &apos;, All
			StringReplace, cdata, cdata, <, &lt;, All
			StringReplace, cdata, cdata, >, &gt;, All
			xml = %xml%%cdata% 
		}
		Else If (!pos := RegExMatch(A_LoopField, "^\/?(?:\w+:)?\w+", tag)) ; if this isn't a valid tag:
		{
			If A_LoopField is not space
				xml = %xml%&lt;%A_LoopField% ; convert to escaped entity value
		}
		Else {
			StringMid, ex, A_LoopField, pos + StrLen(tag) ; get tag name
			If InStr(tag, "/") = 1 { ; if this is a closing tag:
				xml = %xml%</%pre%%ex% ; close tag
				StringGetPos, pos, pre, /, R2
				StringLeft, pre, pre, pos + 1
			}
			Else {
				pre = %pre%%tag%/
				xml = %xml%<%pre%:: %ex%
			}
		}
	}
	StringReplace, doc, xml, `,, &#44;, All ; entity escape commas (which are used as array delimiters)
	NumPut(0, doc := " " . doc, 0, "UChar") ; mask variable from text display with nullbyte
	Return, true ; assume sucessful load by this point
}