Add option to build in "staged" mode

Instead of embedding the .zip, onefile_python.exe will download the
python-embedded zip on each run. Download URL can be set through flags
or the .exe name.

Author: synap5e

README.md

@@ -2,23 +2,63 @@
 
 Run python from a single exe (without needing to extract anything to disk).
 
-This project uses reflective dll loading and nim's `staticRead` to load the python runtime from the executable itself.
+This project uses reflective dll loading and either nim's `staticRead` to load the python runtime from the executable itself, or optionally downloads the embedded zip on launch ("staged" mode).
 Custom (python) import hooks are installed to support loading modules (both native python (.pyc) and extension modules (.pyd)) from the embedded standard library.
 
-## HOWTO
+## Building
+
+Or just download from from the [releases page](https://github.com/synap5e/onefile_python/releases).
 
 0. Set up nim
+
+### Zip embedded in file
+
 1. Download `python-3.10.1-embed-amd64.zip` to the project directory
 2. `nimble build`
 3. Run `onefile_python.exe`
 
-## TODO
+### Download zip on launch ("staged")
+
+Potentially useful if you want a smaller exe.
+
+1. `nimble build -d:staged`
+2. Run `onefile_python.exe`
+
+
+## Usage
+
+```
+onefile_python
 
-Currently the exe just drops to an interactive loop. Modification to run a script or embed a file/module should be trivial. 
+Usage:
+  onefile_python [options] [file] [arg ...]
 
-- [ ] Build option for embedding a python file/module and running that on launch
+Arguments:
+  [file]           Program; read from script file/URL ('-' or empty for interactive) (default: )
+  [arg ...]        Arguments passed to program in sys.argv[1:]
+
+Options:
+  -h, --help
+  -V, --version
+  -c, --command=COMMAND      Program; passed in as string
+```
+`file` can be a http or https URL.
+
+For staged version:
+```
+  -d, --download=DOWNLOAD    Download `python-3.10.1-embed-amd64.zip` from this url (default: https://www.python.org/ftp/python/3.10.1)
+
+```
+
+Alternatively specify the download URL in the app filename e.g. rename `onefile_python.exe` to `blabla(10.0.0.1)foobar.exe` to download python from `https://10.0.0.1/python-3.10.1-embed-amd64.zip`. `blabla` and `foobar` can be any string.
+
+
+## TODO
+
+- [ ] Build option for embedding a python file/module and running that on launch (instead of accepting file/interactive loop)
 - [ ] Support other versions of python than `3.10.1` (autodetect?)
 
+
 ## Similar projects
 
 - [py2exe](https://www.py2exe.org/index.cgi/FrontPage)
@@ -39,7 +79,7 @@ Being simpler, this project should be easier to hack on or learn from.
 
 There's not much to it...
 
-0. Use nim's [staticRead](https://nim-lang.org/docs/system.html#staticRead%2Cstring) to include `python-*-embedded.zip` and `bootstrap.py` inside compiled exe itself.
+0. Use nim's [staticRead](https://nim-lang.org/docs/system.html#staticRead%2Cstring) to include `python-*-embedded.zip` and `bootstrap.py` inside compiled exe itself OR download the zip from a URL.
 1. Use [zippy](https://github.com/guzba/zippy) to access the contents of the archive at runtime.
 2. Use [memlib](https://github.com/khchen/memlib) to perform reflective dll loading of the embedded `python*.dll`. Reflective dll loading allows for loading the dll from memory rather than from disk. Hook `LdrLoadDll` and `K32EnumProcessModules` so other code using the dll can find it. n.b. currently using a fork until https://github.com/khchen/memlib/pull/3 is merged.
 3. Call various functions in the (reflectively) loaded dll to partially initialize python. Configure python to not try to load anything from disk (not absolutely required, but prevents conflicts and means the exe doesn't run any code in the current directory)

config.nims

@@ -1,6 +1,7 @@
-
 --gc:orc
 --define:windows
+when defined(staged):
+  --define:ssl
 when defined(release):
   --define:danger
   --passL:"-Wl,--gc-sections,-flto,-s"  # gc sections, strip, link-time optimization

onefile_python.nim

@@ -19,13 +19,22 @@ const DEBUG = false  # Print debug messages (in nim code, and in python loaders)
 const EMBED_DLL = true  # Use the .dll embedded in the zip archive. If false, will require python310.dll to be in the PATH. If true, debugging may be harder as the dll is reflectively loaded
 
 const PYTHON_EMBEDDED_FILE = "python-3.10.1-embed-amd64.zip"
+when defined(staged):
+    const PYTHON_EMBEDDED_URL = "https://www.python.org/ftp/python/3.10.1"
+
 
 let arg_parser = newParser("onefile_python"):
   help("{prog}")
   flag("-V", "--version")
   option("-c", "--command", help="Program; passed in as string")
   arg("file", default=some(""), help="Program; read from script file/URL ('-' or empty for interactive)")
   arg("arg", nargs=(-1), help="Arguments passed to program in sys.argv[1:]")
+  when defined(staged):
+    option("-d", "--download", help=fmt"Download `{PYTHON_EMBEDDED_FILE}` from this url", default=some(PYTHON_EMBEDDED_URL))
+when defined(staged):
+    const extra_help = fmt"Alternatively specify the download URL in the app filename e.g. `blabla(10.0.0.1)foobar.exe` means download from `https://10.0.0.1/{PYTHON_EMBEDDED_FILE}`."
+else:
+    const extra_help = ""
 
 
 template `//`(a, b: untyped) : untyped = a div b
@@ -46,14 +55,27 @@ proc parse_args: auto =
     except ShortCircuit as e:
         if e.flag == "argparse_help":
             echo arg_parser.help
+            echo extra_help
             quit(1)
     except UsageError:
         stderr.writeLine getCurrentExceptionMsg()
         quit(1)
 
 var opts = parse_args()
 
-const python_310_embedded_zip = staticRead(PYTHON_EMBEDDED_FILE)
+when not defined(staged):
+    const python_310_embedded_zip = staticRead(PYTHON_EMBEDDED_FILE)
+else:
+    var downloadUrl = opts.download & "/" & PYTHON_EMBEDDED_FILE;
+    let appFileName = getAppFilename().splitPath().tail;
+    if appFileName.count("(") == 1 and appFileName.count(")") == 1 and appFileName.find(")") > appFileName.find("("):
+        downloadUrl = "http://" & appFileName.substr(appFileName.find("(") + 1, appFileName.find(")") - 1) & "/" & PYTHON_EMBEDDED_FILE;
+
+    import std/httpclient
+    let client = newHttpClient()
+    echo fmt"Downloading from '{downloadUrl}'..."
+    let python_310_embedded_zip = client.getContent(downloadUrl)
+    echo "\tDone"
 
 var python_embedded = ZipArchive()
 python_embedded.open(newStringStream(python_310_embedded_zip))