[add] initial change implementation

src/doci.xqm

@@ -4,12 +4,12 @@
  @author andy bunce
  :)
 module namespace doci = 'urn:doci';
+(: default line seperator if none found in text :)
+declare variable $doci:default-separator:=file:line-separator();
 
 declare record doci:doci(
   lines as xs:string+,
-  length as xs:integer,  
-  separator? as xs:string,
-  starts? as xs:integer+ 
+  separator? as xs:string
 );
 
 declare record doci:line(
@@ -41,37 +41,89 @@ declare record doci:Range(
 	end as doci:Position
 );
 
+(: 
+@see https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_didChange 
+:)
+declare record doci:TextDocumentContentChangeEvent(
+  text as xs:string,
+  range? as doci:Range
+);
+
 (: create new doci from string :)
 declare function doci:build($text as xs:string)
 as doci:doci{
   let $ls:=doci:separator($text )
-  let $lines:=tokenize($text, '(\r\n?|\n\r?)')
-  let $starts:=hof:scan-left($lines, 0, 
-          fn($res,$line){$res+string-length($ls)+string-length($line)}
-          )
+  let $lines:= doci:split-lines($text)
+  
   return doci:doci(
           lines:= $lines,
-          length:= string-length($text),
-          separator:=$ls,
-          starts:= $starts
+          separator:=$ls
           )
 };
 
-(: line separator, assume all same:)
+(: return full text :)
+declare function doci:text($doci as doci:doci)
+as xs:string{
+  string-join($doci?lines,$doci?separator)
+};
+(: number of lines:)
+declare function doci:lines($doci as doci:doci)
+as xs:string{
+  $doci?lines=>count()
+};
+
+(: detect line separator, assumes all the same:)
 declare function doci:separator($text as xs:string)
 as xs:string?{
 switch () {
    case contains($text,"
") return "
"
    case contains($text,"
") return "
"
    case contains($text,"
") return "
"
-  default return ()
+  default return $doci:default-separator
 }
 };
+(: apply change:)
+declare function doci:change($doci as doci:doci,$change as doci:TextDocumentContentChangeEvent)
+as doci:doci{
+    let $lines:= doci:split-lines($change?text)
+    return if(empty($change?range))
+           then doci:doci($lines,$doci?separator)
+           else let $range:=$change?range
+                let $sline:=$range?start?line
+                let $eline:=$range?end?line
+                return switch(){
+                  case $sline eq $eline and count($lines) eq 1
+                  return let $line:=$doci?lines[$sline+1]
+                         let $new:=substring($line,1,$range?start?character)
+                                   || $lines ||
+                                   substring($line,1+$range?end?character)
+
+                          let $ulines:=( $doci?lines[position() le $sline],
+                                    $new,
+                                    $doci?lines[position() gt 1+$sline]
+                                    )
+                          return doci:doci($ulines, $doci?separator)
+
+                  default return error(#doci:change,"oh")
+                }
+};
+
+declare function doci:split-lines($text as xs:string)
+as xs:string+{
+  if($text eq "") 
+  then $text
+  else tokenize($text, '(\r\n?|\n\r?)')
+};
 
 (: line from pos :)
 declare function doci:lineAt($doci as doci:doci,$pos as xs:integer)
-{
-let $line:=do-until(
+as doci:line {
+let $starts:=hof:scan-left($doci?lines, 0, 
+          fn($res,$line){$res+string-length($doci?seperator)+string-length($line)}
+          ) 
+let $line:=if($pos gt $doci?length)
+           then error(#doci:range,"pos beyond range")
+           else do-until(
           {"min":1,"max":count($doci?lines)},
           fn($r){ 
              let $mid:=round(($r?min+$r?max) div 2,0,"away-from-zero")
@@ -81,5 +133,12 @@ let $line:=do-until(
 },
           fn($r){$r?max eq $r?min}
           )?max
-    return $line    
-};
+          
+    return doci:line(
+      number:= $line,
+      text:=   $doci?lines[$line],
+      from:=   $doci?starts[$line],
+      to:=     -1 
+    )   
+};
+