1 files changed, 158 insertions, 0 deletions
diff --git a/mingling_macros/src/build/comp.rs b/mingling_macros/src/build/comp.rs
new file mode 100644
index 0000000..81a26e8
--- /dev/null
+++ b/mingling_macros/src/build/comp.rs
@@ -0,0 +1,158 @@
+use std::path::PathBuf;
+
+use just_template::tmpl;
+
+/// Represents the shell environment for which the output format is intended.
+///
+/// This is an internal copy of `mingling_core::ShellFlag`, kept private to the
+/// build module because the macros crate must not depend on `mingling_core`.
+/// Which variants are constructed depends on the target OS (`#[cfg]`), so
+/// platform-gated variants may be unused on any given host.
+#[allow(dead_code)]
+#[derive(Default, Debug, Clone, PartialEq, Eq)]
+pub(crate) enum ShellFlag {
+    /// Represents the Bash shell.
+    #[default]
+    Bash,
+    /// Represents the Zsh shell.
+    Zsh,
+    /// Represents the Fish shell.
+    Fish,
+    /// Represents `PowerShell`.
+    Powershell,
+    /// A custom or unsupported shell type, identified by the provided string.
+    Other(String),
+}
+
+const TMPL_COMP_BASH: &str = include_str!("../../tmpls/comps/bash.sh");
+const TMPL_COMP_ZSH: &str = include_str!("../../tmpls/comps/zsh.zsh");
+const TMPL_COMP_FISH: &str = include_str!("../../tmpls/comps/fish.fish");
+const TMPL_COMP_PWSH: &str = include_str!("../../tmpls/comps/pwsh.ps1");
+
+/// Generate shell completion scripts for a given binary name.
+///
+/// On Windows, generates `PowerShell` completion.
+/// On Linux, generates Zsh, Bash, and Fish completions.
+/// Scripts are written to the `OUT_DIR` (or `target/` if `OUT_DIR` is not set).
+///
+/// # Errors
+///
+/// Returns an [`std::io::Error`] if a script cannot be written.
+pub(crate) fn build_comp_scripts(name: &str) -> Result<(), std::io::Error> {
+    #[cfg(target_os = "windows")]
+    {
+        build_comp_script(&ShellFlag::Powershell, name)?;
+        Ok(())
+    }
+
+    #[cfg(target_os = "linux")]
+    {
+        build_comp_script(&ShellFlag::Zsh, name)?;
+        build_comp_script(&ShellFlag::Bash, name)?;
+        build_comp_script(&ShellFlag::Fish, name)?;
+        Ok(())
+    }
+
+    #[cfg(target_os = "macos")]
+    {
+        build_comp_script(&ShellFlag::Zsh, name)?;
+        build_comp_script(&ShellFlag::Bash, name)?;
+        build_comp_script(&ShellFlag::Fish, name)?;
+        Ok(())
+    }
+}
+
+/// Generate a shell completion script for a specific shell.
+///
+/// This function takes a shell flag and a binary name, selects the appropriate
+/// template, substitutes the binary name into the template, and writes the
+/// resulting completion script to the Mingling build directory
+/// (`{target_directory}/mingling/`, resolved via `cargo metadata`).
+///
+/// # Errors
+///
+/// Returns an [`std::io::Error`] if the script cannot be written.
+pub(crate) fn build_comp_script(
+    shell_flag: &ShellFlag,
+    bin_name: &str,
+) -> Result<(), std::io::Error> {
+    let output_dir = comp_output_dir()?;
+    build_comp_script_to(shell_flag, bin_name, &output_dir.to_string_lossy())
+}
+
+/// The directory where completion scripts are written: `{target_directory}/mingling/`.
+fn comp_output_dir() -> Result<PathBuf, std::io::Error> {
+    mingling_pathf::build_output_dir().map_err(|e| std::io::Error::other(e.to_string()))
+}
+
+/// Generate a shell completion script to a specified directory.
+///
+/// This function takes a shell flag, a binary name, and a target directory path,
+/// selects the appropriate template, substitutes the binary name into the template,
+/// and writes the resulting completion script to the specified directory.
+///
+/// # Errors
+///
+/// Returns an [`std::io::Error`] if the script cannot be written.
+pub(crate) fn build_comp_script_to(
+    shell_flag: &ShellFlag,
+    bin_name: &str,
+    target_dir: &str,
+) -> Result<(), std::io::Error> {
+    let (tmpl_str, ext) = get_tmpl(shell_flag);
+    let mut tmpl = just_template::Template::from(tmpl_str);
+    tmpl!(bin_name = bin_name);
+    let target_path = std::path::PathBuf::from(target_dir);
+    std::fs::create_dir_all(&target_path)?;
+    let output_path = target_path.join(format!("{bin_name}_comp{ext}"));
+    std::fs::write(&output_path, tmpl.to_string())
+}
+
+const fn get_tmpl(shell_flag: &ShellFlag) -> (&'static str, &'static str) {
+    match shell_flag {
+        ShellFlag::Bash | ShellFlag::Other(_) => (TMPL_COMP_BASH, ".sh"),
+        ShellFlag::Zsh => (TMPL_COMP_ZSH, ".zsh"),
+        ShellFlag::Fish => (TMPL_COMP_FISH, ".fish"),
+        ShellFlag::Powershell => (TMPL_COMP_PWSH, ".ps1"),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn get_tmpl_bash() {
+        let (tmpl, ext) = get_tmpl(&ShellFlag::Bash);
+        assert_eq!(ext, ".sh");
+        assert!(!tmpl.is_empty(), "bash template should not be empty");
+    }
+
+    #[test]
+    fn get_tmpl_zsh() {
+        let (tmpl, ext) = get_tmpl(&ShellFlag::Zsh);
+        assert_eq!(ext, ".zsh");
+        assert!(!tmpl.is_empty(), "zsh template should not be empty");
+    }
+
+    #[test]
+    fn get_tmpl_fish() {
+        let (tmpl, ext) = get_tmpl(&ShellFlag::Fish);
+        assert_eq!(ext, ".fish");
+        assert!(!tmpl.is_empty(), "fish template should not be empty");
+    }
+
+    #[test]
+    fn get_tmpl_powershell() {
+        let (tmpl, ext) = get_tmpl(&ShellFlag::Powershell);
+        assert_eq!(ext, ".ps1");
+        assert!(!tmpl.is_empty(), "powershell template should not be empty");
+    }
+
+    #[test]
+    fn get_tmpl_other() {
+        let (tmpl, ext) = get_tmpl(&ShellFlag::Other("custom".to_string()));
+        assert_eq!(ext, ".sh");
+        assert!(!tmpl.is_empty(), "fallback template should not be empty");
+    }
+}