RFC-051: Git History Browser UI

Document Information

Overview

This RFC adds a Git History Browser to the Memory feature. It consists of a GitHistoryViewModel, a GitHistoryScreen composable (commit list + filter chips), and a CommitDetailSheet composable (diff view). All git data is sourced from the existing AppGitRepository introduced in RFC-050.

Architecture

New Files

feature/
└── memory/
    └── ui/
        ├── GitHistoryScreen.kt      # commit list + filter chips
        ├── GitHistoryViewModel.kt   # state holder
        └── CommitDetailSheet.kt     # bottom sheet diff view

Add a new Route.GitHistory to the sealed Route class. Register the composable in the nav graph. The entry point is an icon button in MemoryScreen’s top bar.

UI State

data class GitHistoryUiState(
    val commits: List<GitCommitEntry> = emptyList(),
    val isLoading: Boolean = false,
    val selectedFilter: GitHistoryFilter = GitHistoryFilter.ALL,
    val canLoadMore: Boolean = false,
    val selectedCommit: GitCommitEntry? = null,
    val commitDiff: String? = null,
    val isDiffLoading: Boolean = false
)

enum class GitHistoryFilter(val label: String, val path: String?) {
    ALL("All", null),
    MEMORY("Memory", "memory/MEMORY.md"),
    DAILY("Daily Logs", "memory/daily/"),
    FILES("Files", null)  // commits whose message starts with "file:"
}

GitHistoryViewModel

class GitHistoryViewModel(
    private val appGitRepository: AppGitRepository
) : ViewModel() {

    private val _uiState = MutableStateFlow(GitHistoryUiState())
    val uiState: StateFlow<GitHistoryUiState> = _uiState.asStateFlow()

    private var currentOffset = 0
    private val pageSize = 50

    init {
        loadCommits(reset = true)
    }

    fun setFilter(filter: GitHistoryFilter) {
        _uiState.update { it.copy(selectedFilter = filter) }
        loadCommits(reset = true)
    }

    fun loadMore() {
        loadCommits(reset = false)
    }

    fun selectCommit(commit: GitCommitEntry) {
        _uiState.update { it.copy(selectedCommit = commit, commitDiff = null, isDiffLoading = true) }
        viewModelScope.launch {
            val diff = appGitRepository.show(commit.sha)
            _uiState.update { it.copy(commitDiff = diff, isDiffLoading = false) }
        }
    }

    fun dismissDetail() {
        _uiState.update { it.copy(selectedCommit = null, commitDiff = null) }
    }

    private fun loadCommits(reset: Boolean) {
        if (reset) currentOffset = 0
        viewModelScope.launch {
            _uiState.update { it.copy(isLoading = true) }
            val filter = _uiState.value.selectedFilter
            val newCommits = appGitRepository.log(
                path = filter.path,
                maxCount = pageSize + currentOffset
            )
            // For FILES filter: post-filter to commits whose message starts with "file:"
            val filtered = if (filter == GitHistoryFilter.FILES) {
                newCommits.filter { it.message.startsWith("file:") }
            } else {
                newCommits
            }
            val page = if (reset) filtered else filtered.drop(currentOffset)
            currentOffset += page.size
            _uiState.update { state ->
                state.copy(
                    commits = if (reset) filtered else state.commits + page,
                    isLoading = false,
                    canLoadMore = filtered.size == pageSize + (currentOffset - page.size)
                )
            }
        }
    }
}

GitHistoryScreen

@Composable
fun GitHistoryScreen(
    onNavigateBack: () -> Unit,
    viewModel: GitHistoryViewModel = koinViewModel()
) {
    val uiState by viewModel.uiState.collectAsStateWithLifecycle()

    Scaffold(
        topBar = {
            TopAppBar(
                title = { Text("Version History") },
                navigationIcon = {
                    IconButton(onClick = onNavigateBack) {
                        Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = null)
                    }
                }
            )
        }
    ) { padding ->
        Column(modifier = Modifier.padding(padding)) {
            // Filter chips
            FilterChipRow(
                selected = uiState.selectedFilter,
                onSelect = viewModel::setFilter
            )

            when {
                uiState.isLoading && uiState.commits.isEmpty() -> {
                    Box(Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
                        CircularProgressIndicator()
                    }
                }
                uiState.commits.isEmpty() -> {
                    Box(Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
                        Text("No version history yet.")
                    }
                }
                else -> {
                    LazyColumn {
                        items(uiState.commits, key = { it.sha }) { commit ->
                            CommitListItem(
                                commit = commit,
                                onClick = { viewModel.selectCommit(commit) }
                            )
                            HorizontalDivider()
                        }
                        if (uiState.canLoadMore) {
                            item {
                                TextButton(
                                    onClick = viewModel::loadMore,
                                    modifier = Modifier.fillMaxWidth()
                                ) {
                                    Text("Load more")
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    // Commit detail bottom sheet
    uiState.selectedCommit?.let { commit ->
        CommitDetailSheet(
            commit = commit,
            diff = uiState.commitDiff,
            isDiffLoading = uiState.isDiffLoading,
            onDismiss = viewModel::dismissDetail
        )
    }
}

CommitListItem

Each row displays:

  • First line: commit message (single line, ellipsized)
  • Second line: short SHA + formatted timestamp (e.g., a52d630 · Mar 2, 2026 14:30)

FilterChipRow

A LazyRow of FilterChip composables, one per GitHistoryFilter value.

CommitDetailSheet

A ModalBottomSheet containing:

  1. Commit message as a title
  2. SHA + date as a subtitle
  3. If isDiffLoading: CircularProgressIndicator
  4. Else: SelectionContainer { Text(diff, fontFamily = FontFamily.Monospace) } in a vertically scrollable Column

The monospace text is selectable so users can copy specific lines.

Route

// In navigation/Route.kt
data object GitHistory : Route()

composable<Route.GitHistory> {
    GitHistoryScreen(onNavigateBack = { navController.popBackStack() })
}

MemoryScreen Entry Point

Add to the TopAppBar actions of MemoryScreen:

IconButton(onClick = { navController.navigate(Route.GitHistory) }) {
    Icon(Icons.Outlined.History, contentDescription = "Version History")
}

Koin DI

Add to gitModule in GitModule.kt:

viewModel { GitHistoryViewModel(get()) }

Testing

Unit Tests

  • GitHistoryViewModelTest: filter changes trigger reload, selectCommit triggers show(), dismissDetail clears selection, loadMore appends commits

Screenshot Tests (Layer 1C)

  • GitHistoryScreenTest: loading state, empty state, populated list with filter chips
  • CommitDetailSheetTest: loading diff state, populated diff state

Open Questions

None.