custom data view renderer to visualize the spans structure

SpanLogger.kt

package org.wordpress.aztec

import android.text.Spanned
import android.text.TextUtils
import java.util.*

/**
 * Created by hypest on 11/01/17.
 */
object SpanLogger {
    private fun spaces(count: Int, char: String = " "): String {
        return TextUtils.join("", Collections.nCopies(count, char))
    }

    val MARK = 1
    val POINT = 2
    val PARAGRAPH = 3

    @JvmStatic fun logSpans(text: Spanned): String {
        val spans = text.getSpans(0, 9999999, Any::class.java)
        val spansList = Arrays.asList<Any>(*spans)

        val sb = StringBuilder()
        sb.append('\n').append(text.toString().replace('\n', '¶').replace('\u200B', '¬')) // ␤↵↭
        sb.append("  length = " + text.length)

        for (span in spansList) {
            val start = text.getSpanStart(span)
            val end = text.getSpanEnd(span)

            var gap = text.length + 5

            sb.append('\n')

            if (start > 0) {
                sb.append(spaces(start))
                gap -= start
            }

            val spanMode = text.getSpanFlags(span) and Spanned.SPAN_POINT_MARK_MASK
            val leftMode = (spanMode and 0x30) ushr 4
            val rightMode = spanMode and 0x03

            if (end - start > 0) {
                when (leftMode) {
                    MARK -> sb.append('>')
                    POINT -> sb.append('<')
                    PARAGRAPH -> sb.append(if (start == 0) '<' else '>')
                }

                gap--
            } else {
                if (spanMode == Spanned.SPAN_INCLUSIVE_INCLUSIVE) {
                    sb.append('x')
                } else if (spanMode == Spanned.SPAN_INCLUSIVE_EXCLUSIVE) {
                    sb.append('>')
                } else if (spanMode == Spanned.SPAN_EXCLUSIVE_INCLUSIVE) {
                    sb.append('<')
                } else if (spanMode == Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) {
                    sb.append('!')
                } else if (spanMode == Spanned.SPAN_PARAGRAPH) {
                    if (start == 0) {
                        sb.append('!')
                    } else if (start == text.length) {
                        sb.append('<')
                    } else {
                        sb.append('>')
                    }
                }
            }

            if (end - start - 1 > 0) {
                sb.append(spaces(end - start - 1, "-"))
                gap -= end - start - 1
            }

            if (end - start > 0) {
                when (rightMode) {
                    MARK -> sb.append('>')
                    POINT -> sb.append('<')
                    PARAGRAPH -> sb.append(if (end == text.length) '<' else '>')
                }
                gap--
            }

            sb.append(spaces(gap))

            sb.append("   ")
                    .append(String.format("%03d", start))
                    .append(" -> ")
                    .append(String.format("%03d", end))
                    .append(" : ")
                    .append(span.javaClass.simpleName)
        }

        return sb.toString()
    }
}