ai-app/app/androidApp/src/main/kotlin/com/example/aiapp/Attachments.kt

package com.example.aiapp

import android.content.ContentResolver
import android.content.Context
import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.graphics.Matrix
import android.net.Uri
import android.provider.OpenableColumns
import androidx.exifinterface.media.ExifInterface
import java.io.ByteArrayOutputStream
import kotlin.math.max

/**
 * Getting a picked photo to a session, at a size the session can actually take.
 *
 * A phone camera produces twelve megapixels and several megabytes. The Claude API resizes anything
 * larger than 1568px on its long edge before looking at it and refuses images past a much higher
 * bound outright, so a photo sent straight off the camera roll was uploaded whole over the tunnel
 * to be either thrown away or rejected -- which is what "sending an image is broken" was.
 *
 * Shrunk here rather than on the backend, so the bytes that never mattered are never sent: the
 * expensive part on a phone is the upload, not the decode. What the limit *is* comes from the
 * server, per session, because that is where a provider's requirements are known.
 */
suspend fun uploadPickedImage(
    context: Context,
    settings: ServerSettings,
    sessionId: String,
    uri: Uri,
    maxEdge: Int?,
): String {
    val (bytes, mime) = readForUpload(context, uri, maxEdge)
    return uploadAttachment(settings, sessionId, mime, "image") { it.write(bytes) }
}

/**
 * Uploads whatever [uri] names, the way its kind needs. An image goes through [uploadPickedImage]
 * and is shrunk; anything else goes whole, under the name the other app or the file chooser gave
 * it, because the session is told that name rather than shown the bytes.
 *
 * A picture is refused here, before anything is read or sent, when [images] says this session's
 * model cannot read one. Here rather than beside the photo button because this is where every way
 * of attaching meets: the picker, the file chooser, and another app's share sheet -- and only the
 * first of those has a button to disable.
 */
suspend fun uploadPicked(
    context: Context,
    settings: ServerSettings,
    sessionId: String,
    uri: Uri,
    maxEdge: Int?,
    images: ImageSupport,
): String {
    val resolver = context.contentResolver
    val mime = resolver.getType(uri)
    if (mime != null && mime.startsWith("image/")) {
        if (images == ImageSupport.REFUSED) {
            throw ApiException(
                "this session's model can't read pictures, so that one wasn't attached"
            )
        }
        return uploadPickedImage(context, settings, sessionId, uri, maxEdge)
    }
    // Opened before the request starts, so a provider that refuses says so here and not from inside
    // the connection; then streamed, since a trace is bigger than this process should hold at once.
    val source = openSource(resolver, uri)
    val name = displayName(resolver, uri)
    return uploadAttachment(settings, sessionId, mime ?: "application/octet-stream", name) { out ->
        try {
            source.use { it.copyTo(out, COPY_BUFFER) }
        } catch (e: java.io.IOException) {
            // Either side of the copy can fail; the message names the file, which is the part the
            // reader can do something about.
            throw ApiException("couldn't send $name: ${e.message}", cause = e)
        }
    }
}

private const val COPY_BUFFER = 64 * 1024

/**
 * A stream of [uri], or the refusal as the kind the composer reports beside the message.
 *
 * A share arrives with whatever access the other app granted, and a provider that refuses says so
 * with a `SecurityException`; a file gone between the pick and the read is an `IOException`. Both
 * are things the reader can act on.
 */
private fun openSource(resolver: ContentResolver, uri: Uri): java.io.InputStream =
    try {
        resolver.openInputStream(uri)
            ?: throw ApiException("couldn't read ${uri.lastPathSegment ?: uri}: nothing there")
    } catch (e: SecurityException) {
        throw ApiException("couldn't read ${uri.lastPathSegment ?: uri}: no access to it")
    } catch (e: java.io.IOException) {
        throw ApiException("couldn't read ${uri.lastPathSegment ?: uri}: ${e.message}")
    }

/** Everything at [uri]; an image is decoded whole anyway, so it is read whole. */
private fun readAll(resolver: ContentResolver, uri: Uri): ByteArray =
    openSource(resolver, uri).use { it.readBytes() }

/**
 * The name a document provider shows for [uri]. The last path segment is the fallback because a
 * provider's own id for a file is usually a number, which says nothing to the session.
 */
private fun displayName(resolver: ContentResolver, uri: Uri): String {
    resolver.query(uri, arrayOf(OpenableColumns.DISPLAY_NAME), null, null, null)?.use { cursor ->
        val column = cursor.getColumnIndex(OpenableColumns.DISPLAY_NAME)
        if (column >= 0 && cursor.moveToFirst())
            cursor.getString(column)?.let {
                return it
            }
    }
    return uri.lastPathSegment ?: "file"
}

/**
 * The bytes to upload and what they are, scaled down only if they need to be.
 *
 * An image already inside the limit is uploaded exactly as it came, rather than decoded and re-
 * encoded to the same size: a round trip through JPEG loses a little every time. This is also the
 * path a provider with no limit always takes.
 */
private fun readForUpload(context: Context, uri: Uri, maxEdge: Int?): Pair<ByteArray, String> {
    val resolver = context.contentResolver
    val mime = resolver.getType(uri) ?: "image/jpeg"
    val original = readAll(resolver, uri)
    if (maxEdge == null) return original to mime

    val bounds = BitmapFactory.Options().apply { inJustDecodeBounds = true }
    BitmapFactory.decodeByteArray(original, 0, original.size, bounds)
    val longest = max(bounds.outWidth, bounds.outHeight)
    // outWidth is -1 when the bytes are not an image this device can decode. Sent on untouched:
    // this function's job is the size, and refusing something the server might understand is a
    // decision it has no business making.
    if (longest <= 0 || longest <= maxEdge) return original to mime

    // Powers of two first, which is all the decoder can do, and then the exact scale. Decoding the
    // full twelve megapixels only to shrink it is how this runs out of memory on the images it most
    // needs to handle.
    val decode =
        BitmapFactory.Options().apply {
            inSampleSize = Integer.highestOneBit(max(1, longest / maxEdge))
        }
    val decoded =
        BitmapFactory.decodeByteArray(original, 0, original.size, decode) ?: return original to mime
    val scale = maxEdge.toFloat() / max(decoded.width, decoded.height)
    val matrix = Matrix()
    if (scale < 1f) matrix.postScale(scale, scale)
    // The camera writes which way up the picture is into EXIF rather than rotating the pixels, and
    // re-encoding drops the tag -- so a portrait photo would arrive at the model on its side.
    // Applied to the same matrix as the scale, so it costs no second copy of the bitmap.
    matrix.postRotate(exifRotation(original))
    val scaled = Bitmap.createBitmap(decoded, 0, 0, decoded.width, decoded.height, matrix, true)
    val out = ByteArrayOutputStream()
    // JPEG whatever came in: this is a photograph being made smaller, which is what JPEG is for,
    // and a PNG of a resampled photo is several times the size for no visible difference.
    scaled.compress(Bitmap.CompressFormat.JPEG, JPEG_QUALITY, out)
    return out.toByteArray() to "image/jpeg"
}

/** How far to turn the picture so it is the way up it was taken. */
private fun exifRotation(bytes: ByteArray): Float =
    try {
        when (
            ExifInterface(bytes.inputStream())
                .getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL)
        ) {
            ExifInterface.ORIENTATION_ROTATE_90 -> 90f
            ExifInterface.ORIENTATION_ROTATE_180 -> 180f
            ExifInterface.ORIENTATION_ROTATE_270 -> 270f
            else -> 0f
        }
    } catch (_: java.io.IOException) {
        // No EXIF, or none this can read. Upright is the assumption every image without the tag is
        // displayed under anyway.
        0f
    }

/** High enough that resampling is what the reader notices, not the encoder. */
private const val JPEG_QUALITY = 90