Initial commit

app/src/main/java/ani/dantotsu/others/SpoilerPlugin.kt

@@ -0,0 +1,84 @@
+package ani.dantotsu.others
+
+import android.graphics.Color
+import android.text.Spannable
+import android.text.Spanned
+import android.text.TextPaint
+import android.text.style.CharacterStyle
+import android.text.style.ClickableSpan
+import android.view.View
+import android.widget.TextView
+import io.noties.markwon.AbstractMarkwonPlugin
+import io.noties.markwon.utils.ColorUtils
+import java.util.regex.*
+
+class SpoilerPlugin : AbstractMarkwonPlugin() {
+    override fun beforeSetText(textView: TextView, markdown: Spanned) {
+        applySpoilerSpans(markdown as Spannable)
+    }
+
+    private class RedditSpoilerSpan : CharacterStyle() {
+        private var revealed = false
+        override fun updateDrawState(tp: TextPaint) {
+            if (!revealed) {
+                // use the same text color
+                tp.bgColor = Color.DKGRAY
+                tp.color = Color.DKGRAY
+            } else {
+                // for example keep a bit of black background to remind that it is a spoiler
+                tp.bgColor = ColorUtils.applyAlpha(Color.DKGRAY, 25)
+            }
+        }
+
+        fun setRevealed(revealed: Boolean) {
+            this.revealed = revealed
+        }
+    }
+
+    // we also could make text size smaller (but then MetricAffectingSpan should be used)
+    private class HideSpoilerSyntaxSpan : CharacterStyle() {
+        override fun updateDrawState(tp: TextPaint) {
+            // set transparent color
+            tp.color = 0
+        }
+    }
+
+    companion object {
+        private val RE = Pattern.compile("~!.+?!~")
+        private fun applySpoilerSpans(spannable: Spannable) {
+            val text = spannable.toString()
+            val matcher = RE.matcher(text)
+            while (matcher.find()) {
+                val spoilerSpan = RedditSpoilerSpan()
+                val clickableSpan: ClickableSpan = object : ClickableSpan() {
+                    override fun onClick(widget: View) {
+                        spoilerSpan.setRevealed(true)
+                        widget.postInvalidateOnAnimation()
+                    }
+
+                    override fun updateDrawState(ds: TextPaint) {
+                        // no op
+                    }
+                }
+                val s = matcher.start()
+                val e = matcher.end()
+                spannable.setSpan(spoilerSpan, s, e, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)
+                spannable.setSpan(clickableSpan, s, e, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)
+
+                // we also can hide original syntax
+                spannable.setSpan(
+                    HideSpoilerSyntaxSpan(),
+                    s,
+                    s + 2,
+                    Spanned.SPAN_EXCLUSIVE_EXCLUSIVE
+                )
+                spannable.setSpan(
+                    HideSpoilerSyntaxSpan(),
+                    e - 2,
+                    e,
+                    Spanned.SPAN_EXCLUSIVE_EXCLUSIVE
+                )
+            }
+        }
+    }
+}