SpannableStringBuilderExtensions.kt

import android.graphics.Typeface.BOLD
import android.graphics.Typeface.ITALIC
import android.support.annotation.ColorInt
import android.text.Spannable.SPAN_INCLUSIVE_EXCLUSIVE
import android.text.SpannableStringBuilder
import android.text.SpannedString
import android.text.style.*

fun spannable(block: SpannableStringBuilder.() -> Unit): SpannableStringBuilder = SpannableStringBuilder().apply(block)

fun SpannableStringBuilder.appendSpace(): SpannableStringBuilder = append(" ")

fun SpannableStringBuilder.appendWithSpace(charSequence: CharSequence): SpannableStringBuilder {
    append(charSequence)
    appendSpace()
    return this
}

/**
 * Builds new string by populating a newly created [SpannableStringBuilder] using the provided
 * [builderAction] and then converting it to [SpannedString].
 */
inline fun buildSpannedString(builderAction: SpannableStringBuilder.() -> Unit): SpannedString {
    val builder = SpannableStringBuilder()
    builder.builderAction()
    return SpannedString(builder)
}

/**
 * Wrap appended text in [builderAction] in [spans].
 *
 * Note: the spans will only have the correct position if the [builderAction] only appends or
 * replaces text. Inserting, deleting, or clearing the text will cause the span to be placed at
 * an incorrect position.
 */
inline fun SpannableStringBuilder.inSpans(
        vararg spans: Any,
        builderAction: SpannableStringBuilder.() -> Unit
): SpannableStringBuilder {
    val start = length
    builderAction()
    for (span in spans) setSpan(span, start, length, SPAN_INCLUSIVE_EXCLUSIVE)
    return this
}

/**
 * Wrap appended text in [builderAction] in [span].
 *
 * Note: the span will only have the correct position if the `builderAction` only appends or
 * replaces text. Inserting, deleting, or clearing the text will cause the span to be placed at
 * an incorrect position.
 */
inline fun SpannableStringBuilder.inSpans(
        span: Any,
        builderAction: SpannableStringBuilder.() -> Unit
): SpannableStringBuilder {
    val start = length
    builderAction()
    setSpan(span, start, length, SPAN_INCLUSIVE_EXCLUSIVE)
    return this
}

/**
 * Wrap appended text in [builderAction] in a @Style [TextAppearanceSpan].
 *
 * @see SpannableStringBuilder.inSpans
 */
inline fun SpannableStringBuilder.style(
        styleSpan: Any,
        builderAction: SpannableStringBuilder.() -> Unit) =
        inSpans(styleSpan, builderAction = builderAction)


/**
 * Wrap appended text in [builderAction] in a bold [StyleSpan].
 *
 * @see SpannableStringBuilder.inSpans
 */
inline fun SpannableStringBuilder.bold(builderAction: SpannableStringBuilder.() -> Unit) =
        inSpans(StyleSpan(BOLD), builderAction = builderAction)

/**
 * Wrap appended text in [builderAction] in an italic [StyleSpan].
 *
 * @see SpannableStringBuilder.inSpans
 */
inline fun SpannableStringBuilder.italic(builderAction: SpannableStringBuilder.() -> Unit) =
        inSpans(StyleSpan(ITALIC), builderAction = builderAction)

/**
 * Wrap appended text in [builderAction] in an [UnderlineSpan].
 *
 * @see SpannableStringBuilder.inSpans
 */
inline fun SpannableStringBuilder.underline(builderAction: SpannableStringBuilder.() -> Unit) =
        inSpans(UnderlineSpan(), builderAction = builderAction)

/**
 * Wrap appended text in [builderAction] in a [ForegroundColorSpan].
 *
 * @see SpannableStringBuilder.inSpans
 */
inline fun SpannableStringBuilder.color(
        @ColorInt color: Int,
        builderAction: SpannableStringBuilder.() -> Unit
) = inSpans(ForegroundColorSpan(color), builderAction = builderAction)

/**
 * Wrap appended text in [builderAction] in a [BackgroundColorSpan].
 *
 * @see SpannableStringBuilder.inSpans
 */
inline fun SpannableStringBuilder.backgroundColor(
        @ColorInt color: Int,
        builderAction: SpannableStringBuilder.() -> Unit
) = inSpans(BackgroundColorSpan(color), builderAction = builderAction)

/**
 * Wrap appended text in [builderAction] in a [StrikethroughSpan].
 *
 * @see SpannableStringBuilder.inSpans
 */
inline fun SpannableStringBuilder.strikeThrough(builderAction: SpannableStringBuilder.() -> Unit) =
        inSpans(StrikethroughSpan(), builderAction = builderAction)

/**
 * Wrap appended text in [builderAction] in a [RelativeSizeSpan].
 *
 * @see SpannableStringBuilder.inSpans
 */
inline fun SpannableStringBuilder.scale(
        proportion: Float,
        builderAction: SpannableStringBuilder.() -> Unit
) = inSpans(RelativeSizeSpan(proportion), builderAction = builderAction)

/**
 * Wrap appended text in [builderAction] in a [SuperscriptSpan].
 *
 * @see SpannableStringBuilder.inSpans
 */
inline fun SpannableStringBuilder.superscript(builderAction: SpannableStringBuilder.() -> Unit) =
        inSpans(SuperscriptSpan(), builderAction = builderAction)

/**
 * Wrap appended text in [builderAction] in a [SubscriptSpan].
 *
 * @see SpannableStringBuilder.inSpans
 */
inline fun SpannableStringBuilder.subscript(builderAction: SpannableStringBuilder.() -> Unit) =
        inSpans(SubscriptSpan(), builderAction = builderAction)