package org.meshbay.client.photos

import android.content.ContentUris
import android.content.Context
import android.net.Uri
import android.os.Build
import android.provider.MediaStore
import java.io.InputStream

/**
 * The phone's photos and videos, through MediaStore and nothing else.
 *
 * Opened through MediaStore by an application without ACCESS_MEDIA_LOCATION,
 * a file's location is **redacted by the platform** (Android 10+): the EXIF of
 * a photo, and the location boxes of an MP4 or MOV video (MediaProvider's
 * IsoInterface). A whole camera roll going to several people does not say
 * where its owner lives, and nobody had to do anything for that. The manifest
 * does not ask for it.
 *
 * An album is a MediaStore bucket, one directory on the phone; photos and
 * videos in it share its id.
 */
class PhotoSource(private val context: Context) {

    data class Album(
        val id: String, val name: String, val count: Int, val bytes: Long, val camera: Boolean,
        val videos: Int = 0, val videoBytes: Long = 0,
    )

    private val images: Uri =
        if (Build.VERSION.SDK_INT >= 29) MediaStore.Images.Media.getContentUri(MediaStore.VOLUME_EXTERNAL)
        else MediaStore.Images.Media.EXTERNAL_CONTENT_URI
    private val videos: Uri =
        if (Build.VERSION.SDK_INT >= 29) MediaStore.Video.Media.getContentUri(MediaStore.VOLUME_EXTERNAL)
        else MediaStore.Video.Media.EXTERNAL_CONTENT_URI

    /** Every album with photos in it, and with videos too when `withVideos`. */
    fun albums(withVideos: Boolean): List<Album> {
        val by = LinkedHashMap<String, Album>()
        query(images, false, null, null) { p, name, camera ->
            val a = by[p.bucketId]
            by[p.bucketId] = if (a == null) Album(p.bucketId, name, 1, p.size, camera)
                             else a.copy(count = a.count + 1, bytes = a.bytes + p.size, camera = a.camera || camera)
        }
        if (withVideos) query(videos, true, null, null) { p, name, camera ->
            val a = by[p.bucketId] ?: Album(p.bucketId, name, 0, 0, camera)
            by[p.bucketId] = a.copy(videos = a.videos + 1, videoBytes = a.videoBytes + p.size,
                                    camera = a.camera || camera)
        }
        return by.values.sortedWith(compareByDescending<Album> { it.camera }.thenByDescending { it.count + it.videos })
    }

    fun photos(albums: List<String>, withVideos: Boolean): List<Photo> {
        if (albums.isEmpty()) return emptyList()
        val out = ArrayList<Photo>()
        val where = "${MediaStore.Images.Media.BUCKET_ID} IN (${albums.joinToString(",") { "?" }})"
        query(images, false, where, albums.toTypedArray()) { p, _, _ -> out += p }
        if (withVideos) query(videos, true, where, albums.toTypedArray()) { p, _, _ -> out += p }
        return out
    }

    /**
     * The files the photo backup sends, as lowercase `relative/path/name`
     * from the top of their volume: what the files backup leaves out, so
     * nothing is stored twice.
     */
    fun relativePaths(albums: List<String>, withVideos: Boolean): Set<String> {
        if (albums.isEmpty()) return emptySet()
        val out = HashSet<String>()
        val where = "${MediaStore.Images.Media.BUCKET_ID} IN (${albums.joinToString(",") { "?" }})"
        @Suppress("DEPRECATION")
        val cols = if (Build.VERSION.SDK_INT >= 29)
            arrayOf(MediaStore.MediaColumns.RELATIVE_PATH, MediaStore.MediaColumns.DISPLAY_NAME)
        else arrayOf(MediaStore.MediaColumns.DATA)
        for (collection in listOfNotNull(images, videos.takeIf { withVideos })) {
            context.contentResolver.query(collection, cols, where, albums.toTypedArray(), null)?.use { c ->
                while (c.moveToNext()) {
                    val path = if (Build.VERSION.SDK_INT >= 29)
                        (c.getString(0) ?: continue).trim('/') + "/" + (c.getString(1) ?: continue)
                    else volumeRelative(c.getString(0) ?: continue)
                    out += path.lowercase(java.util.Locale.ROOT)
                }
            }
        }
        return out
    }

    fun open(p: Photo): InputStream? =
        context.contentResolver.openInputStream(ContentUris.withAppendedId(if (p.video) videos else images, p.mediaId))

    private fun query(collection: Uri, video: Boolean, where: String?, args: Array<String>?,
                      each: (Photo, String, Boolean) -> Unit) {
        // The same columns exist for images and videos (MediaColumns), and on
        // Android 8 and 9 under the same names in each collection.
        val cols = mutableListOf(
            MediaStore.MediaColumns._ID, MediaStore.MediaColumns.DISPLAY_NAME, MediaStore.MediaColumns.SIZE,
            MediaStore.Images.Media.DATE_TAKEN, MediaStore.MediaColumns.DATE_ADDED,
            MediaStore.MediaColumns.DATE_MODIFIED, MediaStore.Images.Media.BUCKET_ID,
            MediaStore.Images.Media.BUCKET_DISPLAY_NAME, MediaStore.MediaColumns.MIME_TYPE,
        )
        @Suppress("DEPRECATION")
        val location = if (Build.VERSION.SDK_INT >= 29) MediaStore.MediaColumns.RELATIVE_PATH else MediaStore.MediaColumns.DATA
        cols += location
        // A photo or video still being written by the camera is not one yet.
        val pending = if (Build.VERSION.SDK_INT >= 29) "${MediaStore.MediaColumns.IS_PENDING} = 0" else null
        val selection = listOfNotNull(pending, where).joinToString(" AND ").ifEmpty { null }
        context.contentResolver.query(collection, cols.toTypedArray(), selection, args, null)?.use { c ->
            val id = c.getColumnIndexOrThrow(cols[0]); val name = c.getColumnIndexOrThrow(cols[1])
            val size = c.getColumnIndexOrThrow(cols[2]); val taken = c.getColumnIndexOrThrow(cols[3])
            val added = c.getColumnIndexOrThrow(cols[4]); val modified = c.getColumnIndexOrThrow(cols[5])
            val bucket = c.getColumnIndexOrThrow(cols[6]); val bucketName = c.getColumnIndexOrThrow(cols[7])
            val mime = c.getColumnIndexOrThrow(cols[8]); val where2 = c.getColumnIndexOrThrow(cols[9])
            while (c.moveToNext()) {
                val bucketId = c.getString(bucket) ?: continue
                val path = (c.getString(where2) ?: "").replace('\\', '/')
                val display = c.getString(name) ?: ""
                val album = c.getString(bucketName) ?: ""
                // Where it was on the phone, from the top of its volume: what a
                // restore puts it back to (the manifest, §9.12).
                val relPath = if (Build.VERSION.SDK_INT >= 29) path.trim('/') + "/" + display else volumeRelative(path)
                val photo = Photo(
                    c.getLong(id), display, c.getLong(size),
                    if (c.isNull(taken)) 0 else c.getLong(taken), c.getLong(added), c.getLong(modified),
                    bucketId, c.getString(mime) ?: "", video, relPath, album,
                )
                each(photo, album, isCamera(path))
            }
        }
    }

    companion object {
        /** `/storage/emulated/0/Documents/a.jpg` or `/storage/1234-ABCD/x/a.jpg` → the part after the volume. */
        fun volumeRelative(absolute: String): String {
            val m = Regex("^/storage/(?:emulated/\\d+|[^/]+)/(.*)$").matchEntire(absolute)
            return (m?.groupValues?.get(1) ?: absolute).trim('/')
        }

        /** `DCIM/Camera/` (RELATIVE_PATH) or `…/DCIM/Camera/x.jpg` (DATA, before Android 10). */
        fun isCamera(path: String): Boolean =
            path.startsWith("DCIM/Camera") || path.contains("/DCIM/Camera/")
    }
}