Add experimental user parser

src/experimental/parser/slices.nim

@@ -0,0 +1,67 @@
+import std/[macros, htmlgen, unicode]
+import ../types/common
+import ".."/../[formatters, utils]
+
+type
+  ReplaceSliceKind = enum
+    rkRemove, rkUrl, rkHashtag, rkMention
+
+  ReplaceSlice* = object
+    slice: Slice[int]
+    kind: ReplaceSliceKind
+    url, display: string
+
+proc cmp*(x, y: ReplaceSlice): int = cmp(x.slice.a, y.slice.b)
+
+proc dedupSlices*(s: var seq[ReplaceSlice]) =
+  var
+    len = s.len
+    i = 0
+  while i < len:
+    var j = i + 1
+    while j < len:
+      if s[i].slice.a == s[j].slice.a:
+        s.del j
+        dec len
+      else:
+        inc j
+    inc i
+
+proc extractUrls*(result: var seq[ReplaceSlice]; url: Url;
+                  textLen: int; hideTwitter = false) =
+  let
+    link = url.expandedUrl
+    slice = url.indices[0] ..< url.indices[1]
+
+  if hideTwitter and slice.b.succ >= textLen and link.isTwitterUrl:
+    if slice.a < textLen:
+      result.add ReplaceSlice(kind: rkRemove, slice: slice)
+  else:
+    result.add ReplaceSlice(kind: rkUrl, url: link,
+                            display: link.shortLink, slice: slice)
+
+proc replacedWith*(runes: seq[Rune]; repls: openArray[ReplaceSlice];
+                   textSlice: Slice[int]): string =
+  template extractLowerBound(i: int; idx): int =
+    if i > 0: repls[idx].slice.b.succ else: textSlice.a
+
+  result = newStringOfCap(runes.len)
+
+  for i, rep in repls:
+    result.add $runes[extractLowerBound(i, i - 1) ..< rep.slice.a]
+    case rep.kind
+    of rkHashtag:
+      let
+        name = $runes[rep.slice.a.succ .. rep.slice.b]
+        symbol = $runes[rep.slice.a]
+      result.add a(symbol & name, href = "/search?q=%23" & name)
+    of rkMention:
+      result.add a($runes[rep.slice], href = rep.url, title = rep.display)
+    of rkUrl:
+      result.add a(rep.display, href = rep.url)
+    of rkRemove:
+      discard
+
+  let rest = extractLowerBound(repls.len, ^1) ..< textSlice.b
+  if rest.a <= rest.b:
+    result.add $runes[rest]