Route interactive Git through native terminal sessions

Remove Kotlin interactive-add emulation and run patch add via the native Git runtime with PTY-backed session IO.

app/src/main/java/solutions/tretter/githugandroid/GitProcessRunner.kt

@@ -3,12 +3,18 @@ package solutions.tretter.githugandroid
 import android.content.Context
 import android.system.Os
 import java.io.File
+import java.io.InputStream
 import java.nio.file.Files
+import java.util.concurrent.ConcurrentHashMap
+import java.util.concurrent.atomic.AtomicInteger
 
 internal class GitProcessRunner(
     private val context: Context?,
     private val sandboxesRoot: File,
 ) {
+    private val nextHostSessionId = AtomicInteger(1)
+    private val hostSessions = ConcurrentHashMap<Int, HostGitSession>()
+
     private companion object {
         val RequiredGitCommandAliases = listOf(
             "add",
@@ -77,6 +83,29 @@ internal class GitProcessRunner(
         return result
     }
 
+    fun startGitSession(
+        binary: File,
+        workingDir: File,
+        arguments: List<String>,
+        environment: Map<String, String> = emptyMap(),
+    ): GitSessionResult {
+        val gitExecPath = gitExecDirectory(binary)
+        val fullEnvironment = gitEnvironment(binary, workingDir, environment, gitExecPath)
+        return if (context != null) {
+            NativeGitBridge.startGitSession(binary, workingDir, arguments, fullEnvironment)
+        } else {
+            startHostGitSession(binary, workingDir, arguments, fullEnvironment)
+        }
+    }
+
+    fun writeGitSession(sessionId: Int, input: String): GitSessionResult {
+        return if (context != null) {
+            NativeGitBridge.writeGitSession(sessionId, input)
+        } else {
+            writeHostGitSession(sessionId, input)
+        }
+    }
+
     fun runShellProcess(binary: File, workingDir: File, arguments: List<String>): ProcessExecutionResult {
         return try {
             val process = ProcessBuilder(listOf(binary.absolutePath) + arguments)
@@ -119,6 +148,67 @@ internal class GitProcessRunner(
         }
     }
 
+    private fun startHostGitSession(
+        binary: File,
+        workingDir: File,
+        arguments: List<String>,
+        environment: Map<String, String>,
+    ): GitSessionResult {
+        return try {
+            val process = ProcessBuilder(listOf(binary.absolutePath) + arguments)
+                .directory(workingDir)
+                .redirectErrorStream(true)
+                .apply { environment().putAll(environment) }
+                .start()
+            val sessionId = nextHostSessionId.getAndIncrement()
+            hostSessions[sessionId] = HostGitSession(process)
+            readHostGitSessionResult(sessionId, process)
+        } catch (error: Exception) {
+            GitSessionResult(
+                sessionId = 0,
+                running = false,
+                exitCode = -1,
+                outputLines = listOf("Native Git session failed: ${error.message ?: error::class.java.simpleName}"),
+            )
+        }
+    }
+
+    private fun writeHostGitSession(sessionId: Int, input: String): GitSessionResult {
+        val session = hostSessions[sessionId]
+            ?: return GitSessionResult(sessionId, running = false, exitCode = -1, outputLines = listOf("Native Git session is not running."))
+        return try {
+            session.process.outputStream.write(input.toByteArray())
+            session.process.outputStream.flush()
+            readHostGitSessionResult(sessionId, session.process)
+        } catch (error: Exception) {
+            hostSessions.remove(sessionId)
+            GitSessionResult(
+                sessionId = sessionId,
+                running = false,
+                exitCode = -1,
+                outputLines = listOf("Native Git session failed: ${error.message ?: error::class.java.simpleName}"),
+            )
+        }
+    }
+
+    private fun readHostGitSessionResult(sessionId: Int, process: Process): GitSessionResult {
+        val output = StringBuilder()
+        val deadline = System.nanoTime() + 1_000_000_000L
+        do {
+            output.append(process.inputStream.readAvailableText())
+            if (!process.isAlive || output.isNotEmpty()) break
+            Thread.sleep(25)
+        } while (System.nanoTime() < deadline)
+
+        output.append(process.inputStream.readAvailableText())
+        return if (process.isAlive) {
+            GitSessionResult(sessionId = sessionId, running = true, exitCode = null, outputLines = output.toString().toOutputLines())
+        } else {
+            hostSessions.remove(sessionId)
+            GitSessionResult(sessionId = sessionId, running = false, exitCode = process.exitValue(), outputLines = output.toString().toOutputLines())
+        }
+    }
+
     private fun gitExecDirectory(binary: File): File {
         val directory = if (context != null) {
             File(context.filesDir, "git-exec")
@@ -166,6 +256,7 @@ internal class GitProcessRunner(
             put("GIT_COMMITTER_NAME", "GitHug")
             put("GIT_COMMITTER_EMAIL", "githug@example.com")
             put("LC_ALL", "C")
+            put("TERM", "xterm-256color")
             putAll(extraEnvironment)
         }
     }
@@ -232,3 +323,32 @@ internal data class ProcessExecutionResult(
     val exitCode: Int,
     val outputLines: List<String>,
 )
+
+internal data class GitSessionResult(
+    val sessionId: Int,
+    val running: Boolean,
+    val exitCode: Int?,
+    val outputLines: List<String>,
+)
+
+private data class HostGitSession(
+    val process: Process,
+)
+
+private fun InputStream.readAvailableText(): String {
+    val output = StringBuilder()
+    val buffer = ByteArray(4096)
+    while (available() > 0) {
+        val count = read(buffer)
+        if (count <= 0) break
+        output.append(String(buffer, 0, count))
+    }
+    return output.toString()
+}
+
+private fun String.toOutputLines(): List<String> =
+    replace("\r\n", "\n")
+        .replace('\r', '\n')
+        .lineSequence()
+        .toList()
+        .dropLastWhile { it.isEmpty() }