package io.oxygenhub.android.api

/**

 * An account's picture as the hub serves it at `/avatar/{name}`: the

 * picture its owner uploaded, or else the identicon the hub draws from the

 * name. The identicon comes as SVG, which Android cannot draw by itself, so

 * it is read into its hue and cells and drawn natively.

 */

sealed interface Avatar {

    /** An uploaded PNG or JPEG, as served. */

    class Picture(val bytes: ByteArray) : Avatar

    /**

     * The hub's identicon: on a 7 by 7 field of the hue at 45% saturation and

     * 92% lightness, the [cells] (x, y, each 1 to 5) at 65% and 45%.

     */

    data class Identicon(val hue: Int, val cells: Set<Pair<Int, Int>>) : Avatar

    companion object {

        private val FIELD = Regex("""<rect width="7" height="7" fill="hsl\((\d{1,3}),45%,92%\)"/>""")

        private val CELL = Regex("""<rect x="([1-5])" y="([1-5])" width="1" height="1"/>""")

        /**

         * The answer to `/avatar/{name}` by its media type; null for what this

         * app cannot draw (a system account's own mark, or anything unexpected),

         * which then shows as the name's initial.

         */

        fun parse(contentType: String?, bytes: ByteArray): Avatar? =

            when (contentType?.substringBefore(';')?.trim()?.lowercase()) {

                "image/png", "image/jpeg" -> if (bytes.isEmpty()) null else Picture(bytes)

                "image/svg+xml" -> identicon(bytes.decodeToString())

                else -> null

            }

        /** The identicon in the hub's SVG, or null when the SVG is not one. */

        fun identicon(svg: String): Identicon? {

            val hue = FIELD.find(svg)?.groupValues?.get(1)?.toIntOrNull()?.takeIf { it < 360 } ?: return null

            val cells = CELL.findAll(svg).map { it.groupValues[1].toInt() to it.groupValues[2].toInt() }.toSet()

            return Identicon(hue, cells)

        }

    }

}