Implement cli init command

closes #1

omicron/ssg/cli.py

@@ -1,11 +1,14 @@
 import argparse
 import logging
 import sys
+from collections.abc import Callable
 from omicron.ssg.output import OutputError
 from omicron.ssg.site import Site
-from omicron.ssg.config import ConfigError
+from omicron.ssg.config import ConfigError, SiteConfig, DEFAULT_ITEMS_PER_PAGE
 from pathlib import Path
 
+log = logging.getLogger(__name__)
+
 
 class CliError(RuntimeError):
     pass
@@ -46,8 +49,15 @@ def setup_argparse() -> argparse.ArgumentParser:
         default=False,
         help="include draft content",
     )
+
+    # clean command
     subparsers.add_parser("clean", help="remove the output directory")
 
+    # init command
+    subparsers.add_parser(
+        "init", help="create a new site directory", formatter_class=help_formatter
+    )
+
     return parser
 
 
@@ -84,15 +94,80 @@ def clean(args: argparse.Namespace) -> None:
     site.clean()
 
 
+def prompt(
+    label: str,
+    explanation: str | None = None,
+    default: str | None = None,
+    required: bool = True,
+    validate: Callable[[str], bool] | None = None,
+    error: str = "Invalid value.",
+) -> str:
+    if explanation:
+        print(explanation)
+    hint = f" [{default}]" if default is not None else ""
+    while True:
+        value = input(f"{label}{hint}: ").strip()
+        if not value and default is not None:
+            value = default
+        if not value and not required:
+            return ""
+        if not value:
+            print("This field is required.")
+            continue
+        if validate and not validate(value):
+            print(error)
+            continue
+        return value
+
+
+def init(args: argparse.Namespace) -> None:
+    try:
+        args.site.mkdir(parents=True, exist_ok=True)
+    except (FileExistsError, NotADirectoryError) as e:
+        raise CliError(f"{args.site} is not a directory") from e
+    if any(args.site.iterdir()):
+        raise CliError(f"{args.site} is not empty")
+    config_path = args.site / "config.yml"
+
+    name = prompt("Site name")
+    base_url = prompt(
+        "Base URL", "Optional, e.g. https://example.com/blog", required=False
+    )
+    template = prompt("Template", default="plain")
+    items_per_page = prompt(
+        "Items per page",
+        default=str(DEFAULT_ITEMS_PER_PAGE),
+        validate=lambda v: v.isdigit() and int(v) > 0,
+        error="Items per page must be a positive integer.",
+    )
+
+    config = SiteConfig.from_dict(
+        {
+            "name": name,
+            "base_url": base_url,
+            "template": template,
+            "items_per_page": int(items_per_page),
+        }
+    )
+    Site.resolve_template_path(config.template)
+
+    config.to_file(config_path)
+    (args.site / "content").mkdir(exist_ok=True)
+    log.info("Created new site at %s", args.site)
+
+
 def cli() -> None:
     parser = setup_argparse()
     args = parser.parse_args()
-    log_file = getattr(args, "log_file", args.site / "build.log")
+    default_log_file = None if args.command == "init" else args.site / "build.log"
+    log_file = getattr(args, "log_file", default_log_file)
     setup_logging(verbose=bool(args.verbose), log_file=log_file)
     if args.command == "build":
         build(args)
     elif args.command == "clean":
         clean(args)
+    elif args.command == "init":
+        init(args)
     else:
         raise NotImplementedError(f"'{args.command}' command not implemented yet")
 

tests/e2e/test_init.py

@@ -0,0 +1,36 @@
+import subprocess
+import yaml
+
+
+def test_init_creates_site(tmp_path):
+    site_dir = tmp_path / "newsite"
+    result = subprocess.run(
+        ["ossg", "--site", str(site_dir), "init"],
+        input="My Site\nhttps://example.com\n\n\n",
+        capture_output=True,
+        text=True,
+    )
+    assert result.returncode == 0, result.stderr
+
+    config = yaml.safe_load((site_dir / "config.yml").read_text())
+    assert config == {
+        "name": "My Site",
+        "base_url": "https://example.com/",
+        "template": "plain",
+        "items_per_page": 20,
+    }
+    assert (site_dir / "content").is_dir()
+
+
+def test_init_refuses_non_empty_dir(tmp_path):
+    (tmp_path / "some_file").touch()
+
+    result = subprocess.run(
+        ["ossg", "--site", str(tmp_path), "init"],
+        input="My Site\n\n\n\n",
+        capture_output=True,
+        text=True,
+    )
+
+    assert result.returncode == 1
+    assert "is not empty" in result.stdout