Implement downloader and error handling for patch retrieval

po/POTFILES.in

@@ -1 +1,2 @@
 src/main.rs
+src/error.rs

po/patchsplit.pot

@@ -6,9 +6,9 @@
 #, fuzzy
 msgid ""
 msgstr ""
-"Project-Id-Version: patchsplit 0.1.0\n"
+"Project-Id-Version: patchsplit 1.2.0\n"
 "Report-Msgid-Bugs-To: https://github.com/zitzhen/patchsplit/issues\n"
-"POT-Creation-Date: 2026-08-11 15:04+0800\n"
+"POT-Creation-Date: 2026-09-19 14:57+0800\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -34,142 +34,142 @@ msgid "wrote {count} patch file(s) to {directory}"
 msgstr ""
 
 #: src/main.rs
+msgid ""
+"Usage:\n"
+"  patchsplit <owner/repo> <pr-number> [--out <dir>] [--force] [--squash]\n"
+"  patchsplit <owner> <repo> <pr-number> [--out <dir>] [--force] [--squash]\n"
+"  patchsplit <owner/repo> --commit <hash> [--out <dir>] [--force]\n"
+"  patchsplit <owner> <repo> --commit <hash> [--out <dir>] [--force]\n"
+"  patchsplit --gitlab <namespace/project> <mr-number> [--out <dir>] [--"
+"force] [--squash]\n"
+"  patchsplit --gitlab <namespace/project> --commit <hash> [--out <dir>] [--"
+"force]\n"
+"\n"
+"Options:\n"
+"  -o, --out <dir>   Output directory for patch files [default: patches]\n"
+"  -f, --force       Overwrite existing patch files\n"
+"  -s, --squash      Write the net diff as one patch instead of splitting by "
+"commit\n"
+"      --gitlab      Download from gitlab.com (merge requests and commits)\n"
+"      --commit <hash> Download one commit's .patch (short or full hash)\n"
+"  -h, --help        Show this help\n"
+"  -V, --version     Show version\n"
+"\n"
+"Examples:\n"
+"  patchsplit rust-lang/rust 12345\n"
+"  patchsplit openai codex 42 -o pr-42-patches\n"
+"  patchsplit openai/codex 42 --squash\n"
+"  patchsplit zitzhen patchsplit -commit b430113\n"
+"  patchsplit --gitlab zitzhen/patchsplit 1"
+msgstr ""
+
+#: src/error.rs
 msgid "expected a GitHub repository and pull request number"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "repository must use owner/repo form, got {value}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "invalid GitHub repository {kind}: {value}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "pull request number must be a positive integer, got {value}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "expected a GitHub repository with --commit <hash>"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "expected a GitLab project and merge request number"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "expected a GitLab project with --commit <hash>"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid ""
 "GitLab project must use namespace/project form (subgroups allowed), got "
 "{value}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "merge request number must be a positive integer, got {value}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "commit hash must consist of 4 to 40 hexadecimal characters, got {value}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "--commit cannot be combined with --squash"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "missing value for {option}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "unknown option {option}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "curl was not found in PATH"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "failed to run curl: {source}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "download failed with status {status}: {message}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "download failed with status {status}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "download failed: {message}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "download failed"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "downloaded patch is not valid UTF-8: {source}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "downloaded patch is empty"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "downloaded content is not a Git diff"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "failed to create output directory {path}: {source}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid ""
 "refusing to overwrite existing patch file {path}; pass --force to replace it"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "failed to write patch file {path}: {source}"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "owner"
 msgstr ""
 
-#: src/main.rs
+#: src/error.rs
 msgid "repo"
 msgstr ""
-
-#: src/main.rs
-msgid ""
-"Usage:\n"
-"  patchsplit <owner/repo> <pr-number> [--out <dir>] [--force] [--squash]\n"
-"  patchsplit <owner> <repo> <pr-number> [--out <dir>] [--force] [--squash]\n"
-"  patchsplit <owner/repo> --commit <hash> [--out <dir>] [--force]\n"
-"  patchsplit <owner> <repo> --commit <hash> [--out <dir>] [--force]\n"
-"  patchsplit --gitlab <namespace/project> <mr-number> [--out <dir>] "
-"[--force] [--squash]\n"
-"  patchsplit --gitlab <namespace/project> --commit <hash> [--out <dir>] "
-"[--force]\n"
-"\n"
-"Options:\n"
-"  -o, --out <dir>   Output directory for patch files [default: patches]\n"
-"  -f, --force       Overwrite existing patch files\n"
-"  -s, --squash      Write the net diff as one patch instead of splitting by "
-"commit\n"
-"      --gitlab      Download from gitlab.com (merge requests and commits)\n"
-"      --commit <hash> Download one commit's .patch (short or full hash)\n"
-"  -h, --help        Show this help\n"
-"  -V, --version     Show version\n"
-"\n"
-"Examples:\n"
-"  patchsplit rust-lang/rust 12345\n"
-"  patchsplit openai codex 42 -o pr-42-patches\n"
-"  patchsplit openai/codex 42 --squash\n"
-"  patchsplit zitzhen patchsplit -commit b430113\n"
-"  patchsplit --gitlab zitzhen/patchsplit 1"
-msgstr ""

src/config.rs

@@ -0,0 +1,150 @@
+//! Hand-rolled command line parsing (zero extra dependencies).
+//!
+//! [`Options`] holds global flags and grows as new flags are added;
+//! [`Config`] pairs them with the resolved [`Host`], project and target.
+
+use std::path::PathBuf;
+
+use patchsplit::{split_patch_by_commit, PatchPart};
+
+use crate::error::AppError;
+use crate::host::{host_for, Host, Platform, Target};
+
+/// Flag-style options shared by every platform and target.
+#[derive(Debug)]
+pub(crate) struct Options {
+    pub output_dir: PathBuf,
+    pub force: bool,
+    pub squash: bool,
+}
+
+impl Default for Options {
+    fn default() -> Self {
+        Self {
+            output_dir: PathBuf::from("patches"),
+            force: false,
+            squash: false,
+        }
+    }
+}
+
+/// Fully resolved invocation: where to download from and how to write output.
+#[derive(Debug)]
+pub(crate) struct Config {
+    pub platform: Platform,
+    pub project: String,
+    pub target: Target,
+    pub options: Options,
+    host: Box<dyn Host>,
+}
+
+impl Config {
+    pub(crate) fn parse<I>(args: I) -> Result<Self, AppError>
+    where
+        I: IntoIterator<Item = String>,
+    {
+        let mut options = Options::default();
+        let mut gitlab = false;
+        let mut commit = None;
+        let mut positionals = Vec::new();
+        let mut args = args.into_iter();
+
+        while let Some(arg) = args.next() {
+            match arg.as_str() {
+                "-h" | "--help" => return Err(AppError::Help),
+                "-V" | "--version" => return Err(AppError::Version),
+                "-f" | "--force" => options.force = true,
+                "-s" | "--squash" => options.squash = true,
+                "--gitlab" => gitlab = true,
+                "-o" | "--out" => {
+                    let option = arg.as_str().to_string();
+                    let value = args.next().ok_or(AppError::MissingOptionValue(option))?;
+                    options.output_dir = PathBuf::from(value);
+                }
+                value if value.starts_with("--out=") => {
+                    options.output_dir = PathBuf::from(&value["--out=".len()..]);
+                }
+                "-commit" | "--commit" => {
+                    let value = args
+                        .next()
+                        .ok_or(AppError::MissingOptionValue("--commit".to_string()))?;
+                    commit = Some(value);
+                }
+                value if value.starts_with("--commit=") => {
+                    commit = Some(value["--commit=".len()..].to_string());
+                }
+                value if value.starts_with("-commit=") => {
+                    commit = Some(value["-commit=".len()..].to_string());
+                }
+                value if value.starts_with('-') => {
+                    return Err(AppError::UnknownOption(value.to_string()));
+                }
+                value => positionals.push(value.to_string()),
+            }
+        }
+
+        if commit.is_some() && options.squash {
+            return Err(AppError::CommitWithSquash);
+        }
+
+        let platform = if gitlab {
+            Platform::GitLab
+        } else {
+            Platform::GitHub
+        };
+        let host = host_for(platform);
+        let (project, target) = host.resolve(&positionals, commit)?;
+
+        Ok(Self {
+            platform,
+            project,
+            target,
+            options,
+            host,
+        })
+    }
+
+    pub(crate) fn patch_url(&self) -> String {
+        match &self.target {
+            Target::MergeRequest(number) => {
+                let extension = if self.options.squash { "diff" } else { "patch" };
+                self.host.merge_url(&self.project, *number, extension)
+            }
+            Target::Commit(hash) => self.host.commit_url(&self.project, hash),
+        }
+    }
+
+    pub(crate) fn patch_parts(&self, patch: &str) -> Vec<PatchPart> {
+        match &self.target {
+            Target::Commit(hash) => {
+                if patch.trim().is_empty() {
+                    return Vec::new();
+                }
+                // A commit .patch is a single mail-formatted patch; keep it verbatim.
+                vec![PatchPart {
+                    index: 1,
+                    commit: None,
+                    subject: format!("commit {hash}"),
+                    filename: format!("{hash}.patch"),
+                    content: patch.to_string(),
+                }]
+            }
+            Target::MergeRequest(number) => {
+                if !self.options.squash {
+                    return split_patch_by_commit(patch);
+                }
+                if patch.trim().is_empty() {
+                    return Vec::new();
+                }
+                let (subject, filename) = self.host.squash_labels(*number);
+                vec![PatchPart {
+                    index: 1,
+                    commit: None,
+                    subject,
+                    filename,
+                    content: patch.to_string(),
+                }]
+            }
+        }
+    }
+}