Initial release: cd-browser v0.1.0

src/app/ui.py

@@ -0,0 +1,167 @@
+from __future__ import annotations
+
+import curses
+import os
+import sys
+from collections.abc import Iterator
+from contextlib import contextmanager
+from dataclasses import dataclass
+from pathlib import Path
+from typing import TextIO
+
+from app.navigator import Navigator, VisibleEntry
+
+ESCAPE_KEY = 27
+
+
+@dataclass(frozen=True, slots=True)
+class RenderLine:
+    """A rendered navigator row ready for terminal output."""
+
+    text: str
+    is_selected: bool
+
+
+def move_selection(current_index: int, step: int, entry_count: int) -> int:
+    """Move the selected index within the available entry range."""
+
+    if entry_count <= 0:
+        return 0
+
+    return max(0, min(current_index + step, entry_count - 1))
+
+
+def format_entry(entry: VisibleEntry) -> str:
+    """Format a visible entry for terminal display."""
+
+    if entry.is_parent:
+        return entry.name
+
+    indent = "    " * entry.depth
+    indicator = " "
+    if entry.has_children:
+        indicator = "▼" if entry.is_expanded else "▶"
+
+    return f"{indent}{indicator} {entry.name}"
+
+
+def build_render_lines(navigator: Navigator) -> list[RenderLine]:
+    """Build all visible lines for the current navigator state."""
+
+    return [
+        RenderLine(
+            text=format_entry(entry),
+            is_selected=index == navigator.selected_index,
+        )
+        for index, entry in enumerate(navigator.visible_entries)
+    ]
+
+
+class TerminalUI:
+    """Minimal curses UI for the directory navigator MVP."""
+
+    def run(self, navigator: Navigator) -> Path:
+        """Start the interactive session and return the final directory path."""
+
+        with open_terminal_streams() as (input_stream, output_stream):
+            with redirect_standard_streams(input_stream, output_stream):
+                return curses.wrapper(self._run_session, navigator)
+
+    def _run_session(self, stdscr: curses.window, navigator: Navigator) -> Path:
+        curses.curs_set(0)
+        stdscr.keypad(True)
+
+        while True:
+            self._render(stdscr, navigator)
+            key = stdscr.getch()
+
+            if key == ESCAPE_KEY:
+                return navigator.current_path
+
+            if key == curses.KEY_UP:
+                navigator.set_selected_index(
+                    move_selection(
+                        navigator.selected_index,
+                        step=-1,
+                        entry_count=len(navigator.visible_entries),
+                    )
+                )
+                continue
+
+            if key == curses.KEY_DOWN:
+                navigator.set_selected_index(
+                    move_selection(
+                        navigator.selected_index,
+                        step=1,
+                        entry_count=len(navigator.visible_entries),
+                    )
+                )
+                continue
+
+            if key == curses.KEY_RIGHT:
+                navigator.expand_selected_directory()
+                continue
+
+            if key == curses.KEY_LEFT:
+                navigator.collapse_selected_directory()
+                continue
+
+            if key in (curses.KEY_ENTER, 10, 13):
+                navigator.enter_selected_directory()
+
+    def _render(self, stdscr: curses.window, navigator: Navigator) -> None:
+        stdscr.erase()
+        height, width = stdscr.getmaxyx()
+
+        path_text = str(navigator.current_path)
+        stdscr.addnstr(0, 0, path_text, width - 1)
+
+        for row, line in enumerate(build_render_lines(navigator), start=2):
+            if row >= height:
+                break
+
+            attributes = curses.A_REVERSE if line.is_selected else curses.A_NORMAL
+            stdscr.addnstr(row, 0, line.text, width - 1, attributes)
+
+        stdscr.refresh()
+
+
+@contextmanager
+def open_terminal_streams() -> Iterator[tuple[TextIO, TextIO]]:
+    """Open terminal streams suitable for interactive rendering."""
+
+    try:
+        with (
+            open("/dev/tty", encoding="utf-8") as input_stream,
+            open("/dev/tty", "w", encoding="utf-8") as output_stream,
+        ):
+            yield input_stream, output_stream
+            return
+    except OSError:
+        if not sys.stdin.isatty() or not sys.stderr.isatty():
+            raise RuntimeError("Interactive terminal is required") from None
+
+    yield sys.stdin, sys.stderr
+
+
+@contextmanager
+def redirect_standard_streams(
+    input_stream: TextIO, output_stream: TextIO
+) -> Iterator[None]:
+    """Temporarily redirect stdin and stdout to terminal-backed streams."""
+
+    sys.stdout.flush()
+    sys.stderr.flush()
+
+    original_stdin = os.dup(0)
+    original_stdout = os.dup(1)
+
+    try:
+        os.dup2(input_stream.fileno(), 0)
+        os.dup2(output_stream.fileno(), 1)
+        yield
+    finally:
+        os.dup2(original_stdin, 0)
+        os.dup2(original_stdout, 1)
+        os.close(original_stdin)
+        os.close(original_stdout)