VesiscanClinicalAndroid/app/src/main/java/com/medithings/vesiscan/firmware/FirmwarePackage.kt

/*
 * MEDiDFU — VesiSeek firmware updater
 *
 * Unpacks the DFU archive bundled in assets/ and extracts the signed MCUboot image.
 *
 * Author: Charles KWON OhJun <charleskwon@medithings.co.kr>
 * MEDiThings Inc.
 */
package com.medithings.vesiscan.firmware
import android.content.Context
import org.json.JSONObject
import java.io.ByteArrayOutputStream
import java.util.zip.ZipInputStream

/** A signed MCUboot application image unpacked from a `dfu_application_*.zip`. */
data class FirmwarePackage(
    val assetName: String,
    val imageFileName: String,
    /** `version_MCUBOOT` from the manifest, e.g. "0.0.2+35". Empty when the manifest omits it. */
    val version: String,
    val image: ByteArray,
) {
    val sizeBytes: Int get() = image.size

    // Generated equals/hashCode would compare the ByteArray by reference; identify the package by
    // its source instead.
    override fun equals(other: Any?): Boolean =
        this === other || (other is FirmwarePackage &&
                assetName == other.assetName &&
                imageFileName == other.imageFileName &&
                version == other.version &&
                image.size == other.image.size)

    override fun hashCode(): Int =
        (((assetName.hashCode() * 31 + imageFileName.hashCode()) * 31) + version.hashCode()) * 31 +
                image.size
}

/**
 * Reads a DFU zip bundled in `assets/`.
 *
 * The zip is the nRF Connect SDK / Zephyr layout: a `manifest.json` listing the images plus the
 * signed binaries themselves. The application image (`image_index` 0, or `type` "application") is
 * the one uploaded over SMP.
 */
object FirmwareLoader {

    const val DEFAULT_ASSET = "dfu_application_2+35.zip"

    private const val MANIFEST = "manifest.json"

    @Throws(IllegalStateException::class)
    fun loadFromAssets(context: Context, assetName: String = DEFAULT_ASSET): FirmwarePackage {
        val entries = readZipEntries(context, assetName)

        val manifestBytes = entries.entries
            .firstOrNull { it.key.equals(MANIFEST, ignoreCase = true) }
            ?.value
            ?: error("$MANIFEST not found in $assetName")

        val files = JSONObject(String(manifestBytes, Charsets.UTF_8)).optJSONArray("files")
            ?: error("$MANIFEST has no \"files\" array")
        check(files.length() > 0) { "$MANIFEST lists no images" }

        var chosen = files.getJSONObject(0)
        for (i in 0 until files.length()) {
            val entry = files.getJSONObject(i)
            if (entry.optString("image_index") == "0" ||
                entry.optString("type").equals("application", ignoreCase = true)
            ) {
                chosen = entry
                break
            }
        }

        val fileName = chosen.optString("file")
        check(fileName.isNotEmpty()) { "$MANIFEST entry has no \"file\" field" }
        val image = entries[fileName] ?: error("$fileName listed in $MANIFEST but missing from the zip")
        check(image.isNotEmpty()) { "$fileName is empty" }

        return FirmwarePackage(
            assetName = assetName,
            imageFileName = fileName,
            version = chosen.optString("version_MCUBOOT"),
            image = image,
        )
    }

    private fun readZipEntries(context: Context, assetName: String): Map<String, ByteArray> {
        val entries = LinkedHashMap<String, ByteArray>()
        ZipInputStream(context.assets.open(assetName)).use { zip ->
            val buffer = ByteArray(16 * 1024)
            while (true) {
                val entry = zip.nextEntry ?: break
                if (entry.isDirectory) {
                    zip.closeEntry()
                    continue
                }
                val out = ByteArrayOutputStream()
                while (true) {
                    val read = zip.read(buffer)
                    if (read < 0) break
                    out.write(buffer, 0, read)
                }
                entries[entry.name] = out.toByteArray()
                zip.closeEntry()
            }
        }
        return entries
    }
}