feat(import): add Ampersand importer

CHANGELOG.md

@@ -6,6 +6,14 @@ uses semantic versioning (`MAJOR.MINOR.PATCH`).
 
 ## [Unreleased]
 
+### Added
+
+- **Import from Ampersand.** Settings > Data now has an "Import from Ampersand"
+  option. Choose your Ampersand `.json` export and pick what to bring across
+  (members, custom fronts, tags, custom fields, front history, journals, notes,
+  board messages and polls, reminders, images, and Ampersand systems as groups);
+  the import runs in the background and shows a summary when it finishes.
+
 ### Security
 
 - **Your login credentials only ever go to your own server now.** The app used to

sheaf/app/src/main/java/systems/lupine/sheaf/data/api/SheafApiService.kt

@@ -525,6 +525,12 @@ interface SheafApiService {
         @Part file: MultipartBody.Part,
     ): PluralSpacePreviewSummary
 
+    @Multipart
+    @POST("/v1/import/ampersand/preview")
+    suspend fun previewAmpersandImport(
+        @Part file: MultipartBody.Part,
+    ): AmpersandPreviewSummary
+
     /**
      * Preview an OpenPlural v0.1 import. Accepts a bare `.json` export or an
      * `.openplural.zip` bundle (the endpoint sniffs the zip magic). Reuses the

sheaf/app/src/main/java/systems/lupine/sheaf/data/model/Models.kt

@@ -1002,8 +1002,32 @@ object ImportJobSource {
     // and the .openplural.zip bundle; the runner sniffs the zip magic and
     // unpacks images when present (no separate archive source like Sheaf).
     const val OPENPLURAL_FILE = "openplural_file"
+    const val AMPERSAND_FILE = "ampersand_file"
 }
 
+// ── Ampersand import ──────────────────────────────────────────────────────────
+//
+// Ampersand exports a plain .json file. The preview reports category counts
+// only (no per-member list), so selective member import isn't offered on
+// Android; every real member is imported. `groups` imports Ampersand systems as
+// Sheaf groups; `board_messages` also gates polls.
+@JsonClass(generateAdapter = true)
+data class AmpersandPreviewSummary(
+    @Json(name = "system_count") val systemCount: Int = 0,
+    @Json(name = "member_count") val memberCount: Int = 0,
+    @Json(name = "custom_front_count") val customFrontCount: Int = 0,
+    @Json(name = "front_history_count") val frontHistoryCount: Int = 0,
+    @Json(name = "tag_count") val tagCount: Int = 0,
+    @Json(name = "custom_field_count") val customFieldCount: Int = 0,
+    @Json(name = "journal_count") val journalCount: Int = 0,
+    @Json(name = "note_count") val noteCount: Int = 0,
+    @Json(name = "board_message_count") val boardMessageCount: Int = 0,
+    @Json(name = "poll_count") val pollCount: Int = 0,
+    @Json(name = "reminder_count") val reminderCount: Int = 0,
+    @Json(name = "asset_count") val assetCount: Int = 0,
+    @Json(name = "limit_warnings") val limitWarnings: List<String> = emptyList(),
+)
+
 // ── Export ──────────────────────────────────────────────────────────────────
 
 /** Async full-backup (with images) request. Step-up: password always, plus

sheaf/app/src/main/java/systems/lupine/sheaf/ui/SheafApp.kt

@@ -84,6 +84,7 @@ object Routes {
     const val PS_IMPORT      = "settings/import/pluralspace"
     const val PRISM_IMPORT   = "settings/import/prism"
     const val OPENPLURAL_IMPORT = "settings/import/openplural"
+    const val AMPERSAND_IMPORT = "settings/import/ampersand"
     const val IMPORT_HISTORY = "settings/import/history"
     const val IMPORT_DETAIL  = "settings/import/history/{jobId}"
     const val CUSTOM_FIELDS  = "settings/fields"
@@ -529,6 +530,7 @@ fun SheafApp(
                     onNavigateToPluralSpaceImport = { navController.navigate(Routes.PS_IMPORT) },
                     onNavigateToPrismImport = { navController.navigate(Routes.PRISM_IMPORT) },
                     onNavigateToOpenPluralImport = { navController.navigate(Routes.OPENPLURAL_IMPORT) },
+                    onNavigateToAmpersandImport = { navController.navigate(Routes.AMPERSAND_IMPORT) },
                     onNavigateToImportHistory = { navController.navigate(Routes.IMPORT_HISTORY) },
                 )
             }
@@ -588,6 +590,11 @@ fun SheafApp(
                     onNavigateUp = { navController.navigateUp() },
                 )
             }
+            composable(Routes.AMPERSAND_IMPORT) {
+                systems.lupine.sheaf.ui.ampersandimport.AmpersandImportScreen(
+                    onNavigateUp = { navController.navigateUp() },
+                )
+            }
             composable(Routes.EXPORT_DATA) {
                 systems.lupine.sheaf.ui.export.ExportDataScreen(
                     onNavigateUp = { navController.navigateUp() },

sheaf/app/src/main/java/systems/lupine/sheaf/ui/ampersandimport/AmpersandImportScreen.kt

@@ -0,0 +1,278 @@
+package systems.lupine.sheaf.ui.ampersandimport
+
+import androidx.activity.compose.rememberLauncherForActivityResult
+import androidx.activity.result.contract.ActivityResultContracts
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material.icons.outlined.FileOpen
+import androidx.compose.material3.*
+import androidx.compose.runtime.*
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import androidx.hilt.navigation.compose.hiltViewModel
+import systems.lupine.sheaf.data.model.AmpersandPreviewSummary
+import systems.lupine.sheaf.ui.components.ErrorBanner
+import systems.lupine.sheaf.ui.components.SectionHeader
+import systems.lupine.sheaf.ui.components.SheafTopAppBar
+import systems.lupine.sheaf.ui.importcommon.ImportResult
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun AmpersandImportScreen(
+    onNavigateUp: () -> Unit,
+    viewModel: AmpersandImportViewModel = hiltViewModel(),
+) {
+    val state by viewModel.state.collectAsState()
+
+    val filePicker = rememberLauncherForActivityResult(
+        ActivityResultContracts.OpenDocument()
+    ) { uri -> uri?.let { viewModel.pickFile(it) } }
+
+    Scaffold(
+        contentWindowInsets = WindowInsets(0),
+        topBar = {
+            SheafTopAppBar(
+                title = { Text("Import from Ampersand") },
+                navigationIcon = {
+                    IconButton(onClick = onNavigateUp) {
+                        Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = "Back")
+                    }
+                },
+            )
+        },
+    ) { padding ->
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(padding)
+                .verticalScroll(rememberScrollState())
+                .padding(horizontal = 16.dp, vertical = 12.dp),
+            verticalArrangement = Arrangement.spacedBy(12.dp),
+        ) {
+            if (state.error != null) ErrorBanner(state.error!!)
+
+            when {
+                state.result != null -> ResultSection(
+                    result = state.result!!,
+                    onImportAnother = { viewModel.reset() },
+                )
+                state.isImporting -> CenterSpinner("Importing…")
+                state.preview != null -> PreviewSection(
+                    fileName = state.fileName!!,
+                    preview = state.preview!!,
+                    options = state.options,
+                    onUpdateOptions = { viewModel.updateOptions(it) },
+                    onImport = { viewModel.runImport() },
+                    onChangeFile = { filePicker.launch(arrayOf("*/*")) },
+                )
+                state.isPreviewing -> CenterSpinner("Reading file…")
+                else -> FilePickSection(onPick = { filePicker.launch(arrayOf("*/*")) })
+            }
+        }
+    }
+}
+
+@Composable
+private fun CenterSpinner(label: String) {
+    Box(Modifier.fillMaxWidth().padding(vertical = 48.dp), contentAlignment = Alignment.Center) {
+        Column(horizontalAlignment = Alignment.CenterHorizontally, verticalArrangement = Arrangement.spacedBy(16.dp)) {
+            CircularProgressIndicator()
+            Text(label, style = MaterialTheme.typography.bodyMedium, color = MaterialTheme.colorScheme.onSurfaceVariant)
+        }
+    }
+}
+
+@Composable
+private fun FilePickSection(onPick: () -> Unit) {
+    Column(
+        modifier = Modifier.fillMaxWidth().padding(top = 32.dp),
+        horizontalAlignment = Alignment.CenterHorizontally,
+        verticalArrangement = Arrangement.spacedBy(16.dp),
+    ) {
+        Icon(
+            Icons.Outlined.FileOpen,
+            contentDescription = null,
+            modifier = Modifier.size(52.dp),
+            tint = MaterialTheme.colorScheme.onSurfaceVariant.copy(alpha = 0.5f),
+        )
+        Text("Choose your Ampersand export to get started.", style = MaterialTheme.typography.bodyMedium, color = MaterialTheme.colorScheme.onSurfaceVariant)
+        Button(onClick = onPick) { Text("Choose file") }
+        Text(
+            "In Ampersand, open Settings → Import & export → Export, and save the " +
+                ".json file. Then select it here.",
+            style = MaterialTheme.typography.bodySmall,
+            color = MaterialTheme.colorScheme.onSurfaceVariant.copy(alpha = 0.7f),
+        )
+    }
+}
+
+@Composable
+private fun PreviewSection(
+    fileName: String,
+    preview: AmpersandPreviewSummary,
+    options: AmpersandImportOptions,
+    onUpdateOptions: (AmpersandImportOptions.() -> AmpersandImportOptions) -> Unit,
+    onImport: () -> Unit,
+    onChangeFile: () -> Unit,
+) {
+    Row(verticalAlignment = Alignment.CenterVertically, horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+        Text(fileName, style = MaterialTheme.typography.bodyMedium, modifier = Modifier.weight(1f), maxLines = 1)
+        TextButton(onClick = onChangeFile) { Text("Change") }
+    }
+
+    HorizontalDivider()
+    SectionHeader("What to import")
+
+    // Members always import; shown for context, not as a toggle.
+    if (preview.memberCount > 0) {
+        Text(
+            "Members (${preview.memberCount})",
+            style = MaterialTheme.typography.bodyMedium,
+            fontWeight = FontWeight.Medium,
+        )
+    }
+
+    if (preview.systemCount > 0) {
+        ImportToggleRow(
+            label = "Systems as groups (${preview.systemCount})",
+            checked = options.groups,
+            onCheckedChange = { onUpdateOptions { copy(groups = it) } },
+        )
+    }
+    if (preview.customFrontCount > 0) {
+        ImportToggleRow(
+            label = "Custom fronts (${preview.customFrontCount})",
+            checked = options.customFronts,
+            onCheckedChange = { onUpdateOptions { copy(customFronts = it) } },
+        )
+    }
+    if (preview.tagCount > 0) {
+        ImportToggleRow(
+            label = "Tags (${preview.tagCount})",
+            checked = options.tags,
+            onCheckedChange = { onUpdateOptions { copy(tags = it) } },
+        )
+    }
+    if (preview.customFieldCount > 0) {
+        ImportToggleRow(
+            label = "Custom fields (${preview.customFieldCount})",
+            checked = options.customFields,
+            onCheckedChange = { onUpdateOptions { copy(customFields = it) } },
+        )
+    }
+    if (preview.frontHistoryCount > 0) {
+        ImportToggleRow(
+            label = "Front history (${preview.frontHistoryCount} entries)",
+            checked = options.frontHistory,
+            onCheckedChange = { onUpdateOptions { copy(frontHistory = it) } },
+        )
+    }
+    if (preview.journalCount > 0) {
+        ImportToggleRow(
+            label = "Journal entries (${preview.journalCount})",
+            checked = options.journals,
+            onCheckedChange = { onUpdateOptions { copy(journals = it) } },
+        )
+    }
+    if (preview.noteCount > 0) {
+        ImportToggleRow(
+            label = "Notes (${preview.noteCount})",
+            checked = options.notes,
+            onCheckedChange = { onUpdateOptions { copy(notes = it) } },
+        )
+    }
+    if (preview.boardMessageCount > 0 || preview.pollCount > 0) {
+        val label = buildString {
+            append("Board messages")
+            if (preview.boardMessageCount > 0) append(" (${preview.boardMessageCount})")
+            if (preview.pollCount > 0) append(" & polls (${preview.pollCount})")
+        }
+        ImportToggleRow(
+            label = label,
+            checked = options.boardMessages,
+            onCheckedChange = { onUpdateOptions { copy(boardMessages = it) } },
+        )
+    }
+    if (preview.reminderCount > 0) {
+        ImportToggleRow(
+            label = "Reminders (${preview.reminderCount})",
+            checked = options.reminders,
+            onCheckedChange = { onUpdateOptions { copy(reminders = it) } },
+        )
+    }
+    if (preview.assetCount > 0) {
+        ImportToggleRow(
+            label = "Images (${preview.assetCount})",
+            checked = options.images,
+            onCheckedChange = { onUpdateOptions { copy(images = it) } },
+        )
+    }
+
+    preview.limitWarnings.forEach { warning ->
+        SkippedNote(warning)
+    }
+
+    Spacer(Modifier.height(4.dp))
+
+    Button(onClick = onImport, modifier = Modifier.fillMaxWidth().height(52.dp)) {
+        Text("Import")
+    }
+}
+
+@Composable
+private fun ImportToggleRow(label: String, checked: Boolean, onCheckedChange: (Boolean) -> Unit) {
+    Row(verticalAlignment = Alignment.CenterVertically, modifier = Modifier.fillMaxWidth()) {
+        Checkbox(checked = checked, onCheckedChange = onCheckedChange)
+        Text(label, style = MaterialTheme.typography.bodyMedium)
+    }
+}
+
+@Composable
+private fun SkippedNote(text: String) {
+    Row(verticalAlignment = Alignment.CenterVertically, modifier = Modifier.fillMaxWidth()) {
+        Spacer(Modifier.width(12.dp))
+        Text(text, style = MaterialTheme.typography.bodySmall, color = MaterialTheme.colorScheme.onSurfaceVariant)
+    }
+}
+
+@Composable
+private fun ResultSection(result: ImportResult, onImportAnother: () -> Unit) {
+    SectionHeader("Import complete")
+
+    val rows = result.rows()
+    ElevatedCard(modifier = Modifier.fillMaxWidth()) {
+        Column(modifier = Modifier.padding(16.dp), verticalArrangement = Arrangement.spacedBy(6.dp)) {
+            if (rows.isEmpty()) {
+                Text("Nothing new to import.", style = MaterialTheme.typography.bodyMedium)
+            } else {
+                rows.forEach { (label, count) -> ResultRow(label, count) }
+            }
+        }
+    }
+
+    if (result.warnings.isNotEmpty()) {
+        SectionHeader("Warnings")
+        result.warnings.forEach { warning ->
+            Text("• $warning", style = MaterialTheme.typography.bodySmall, color = MaterialTheme.colorScheme.onSurfaceVariant)
+        }
+    }
+
+    Spacer(Modifier.height(4.dp))
+
+    OutlinedButton(onClick = onImportAnother, modifier = Modifier.fillMaxWidth()) {
+        Text("Import another file")
+    }
+}
+
+@Composable
+private fun ResultRow(label: String, count: Int) {
+    Row(modifier = Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.SpaceBetween) {
+        Text(label, style = MaterialTheme.typography.bodyMedium)
+        Text(count.toString(), style = MaterialTheme.typography.bodyMedium, fontWeight = FontWeight.Medium)
+    }
+}