monochromatic-git-policy-cli 0.5.16

//! What:
//!  `git cli-git migrate-to-subvolume`: find the repository's main checkout from the working directory, run the
//!  requested mode (migrate, rollback, remove the old tree) and turn the result into an exit status and text.
//! Why:
//!  The command runs for minutes (the real checkout took about sixteen minutes of passes), so progress lines go to
//!  standard error as they happen; refusals and failures end with the cause and every way forward. Exit status 0 means
//!  done, already done or previewed, 1 means a condition refused it before anything changed, and 2 means a step
//!  failed after the journal began, with the instruction to run the command again or to roll back. The main checkout is
//!  found by reading `.git` in process (a directory, or a gitfile naming the common directory), never by asking Git.
//!
//! In TS you'd write (pseudocode):
//! ```ts
//! const code = await execute({ platform, args, root, interrupt, say });
//! ```

use super::action::{Action, ENGINE_FAILURE_EXIT_CODE};
use super::subvolume_arguments::{MIGRATE_HELP, MigrateArguments, MigrateMode};
use super::subvolume_error::{Interrupt, MigrateError};
use super::subvolume_migrate::{MigrateOptions, Verdict, migrate};
use super::subvolume_platform::{LinuxPlatform, Platform};
use super::subvolume_preflight::{Refusal, layout_of};
use super::subvolume_rollback::{remove_old_tree, rollback};
use super::subvolume_run::Run;
use std::io::Write;
use std::path::{Path, PathBuf};

/// The exit status of a refusal: a condition stood in the way and nothing was changed.
pub const REFUSED_EXIT_CODE: i32 = 1;

/// What:
///  The main checkout of the repository that contains `start`, found without starting Git.
/// Why:
///   Walk up to the first `.git`. A directory there marks the main checkout. A file there is a linked worktree's
///  gitfile (`gitdir: <admin directory>`); the administrative directory's `commondir` names the common directory,
///  whose parent is the main checkout when the common directory is called `.git`. Anything else (a bare repository, a
///  submodule, an unreadable gitfile) is reported, because converting the wrong directory would be harmful.
///
/// In TS you'd write (pseudocode):
/// ```ts
/// function mainCheckoutRoot(start: string): string; // throws with the reason
/// ```
pub fn main_checkout_root(start: &Path) -> Result<PathBuf, String> {
    let real: PathBuf = std::fs::canonicalize(start).map_err(|error: std::io::Error| { return format!("cannot resolve {}: {error}", start.display()); })?;
    let mut directory: PathBuf = real.clone();
    loop {
        let dot_git: PathBuf = directory.join(".git");
        if let Ok(metadata) = std::fs::symlink_metadata(&dot_git) {
            if metadata.is_dir() {
                return Ok(directory);
            }
            return common_root_of_gitfile(dot_git.as_path());
        }
        let Some(parent) = directory.parent() else {
            return Err(format!("{} is not inside a Git working tree (no .git above it)", real.display()));
        };
        directory = parent.to_path_buf();
    }
}

/// Read a linked worktree's gitfile and return the main checkout it belongs to.
fn common_root_of_gitfile(gitfile: &Path) -> Result<PathBuf, String> {
    let text: String = std::fs::read_to_string(gitfile).map_err(|error: std::io::Error| { return format!("cannot read {}: {error}", gitfile.display()); })?;
    let Some(named) = text.trim().strip_prefix("gitdir:") else {
        return Err(format!("{} is not a gitfile (no `gitdir:` line)", gitfile.display()));
    };
    let base: &Path = gitfile.parent().unwrap_or(Path::new("/"));
    let admin: PathBuf = base.join(named.trim());
    let common_text: String = std::fs::read_to_string(admin.join("commondir"))
        .map_err(|_| { return format!("{} is not a linked worktree's gitfile ({} has no commondir), so this is not a main checkout or a linked worktree of one", gitfile.display(), admin.display()); })?;
    let common: PathBuf = std::fs::canonicalize(admin.join(common_text.trim())).map_err(|error: std::io::Error| { return format!("cannot resolve the common directory: {error}"); })?;
    if common.file_name().is_none_or(|name: &std::ffi::OsStr| { return name != ".git"; }) {
        return Err(format!("the common directory {} is not named .git, so the repository has no main checkout directory to convert", common.display()));
    }
    return common.parent().map(Path::to_path_buf).ok_or_else(|| { return String::from("the common directory has no parent"); });
}

/// Write the refusals in plain words.
fn say_refusals(say: &mut dyn FnMut(&str), refusals: &[Refusal]) {
    for refusal in refusals {
        say(format!("git cli-git migrate-to-subvolume: refused: {}", refusal.cause).as_str());
        say(format!("  What to do: {}", refusal.remedy).as_str());
    }
    say("Nothing was changed.");
}

/// What:
///  Run the requested mode against a root and return the exit status.
///  `say` receives every line; the platform and interrupt are injected so controls run it on any filesystem.
/// Why:
///   One function holds the status mapping, so the controls check the real command's behavior.
///
/// In TS you'd write (pseudocode):
/// ```ts
/// const code = await execute(platform, args, root, interrupt, say);
/// ```
pub fn execute(platform: &dyn Platform, arguments: &MigrateArguments, root: &Path, interrupt: &Interrupt, say: &mut dyn FnMut(&str)) -> i32 {
    let outcome: Result<i32, MigrateError> = run_mode(platform, arguments, root, interrupt, &mut *say);
    match outcome {
        Ok(code) => return code,
        Err(error) => {
            let journal: String = layout_of(root).map(|layout| { return layout.journal_path.display().to_string(); }).unwrap_or_default();
            say(format!("git cli-git migrate-to-subvolume: failed: {error}").as_str());
            say(format!("The journal {journal} records the steps that finished. Run the command again to resume from there, or add --rollback to restore the original directory.").as_str());
            return ENGINE_FAILURE_EXIT_CODE;
        }
    }
}

/// The three modes, as a result so `execute` maps every error the same way.
fn run_mode(platform: &dyn Platform, arguments: &MigrateArguments, root: &Path, interrupt: &Interrupt, say: &mut dyn FnMut(&str)) -> Result<i32, MigrateError> {
    if arguments.mode == MigrateMode::Migrate {
        let options: MigrateOptions = MigrateOptions { dry_run: arguments.dry_run, nested_worktrees: arguments.nested_worktrees, refresh_indexes: arguments.refresh_indexes };
        let verdict: Verdict = migrate(platform, root, options, interrupt, &mut *say)?;
        if let Verdict::Refused(refusals) = verdict {
            say_refusals(say, refusals.as_slice());
            return Ok(REFUSED_EXIT_CODE);
        }
        return Ok(0);
    }
    let Some(layout) = layout_of(root) else {
        return Err(MigrateError::Journal(format!("{} has no parent directory", root.display())));
    };
    let mut run: Run<'_> = Run::open(platform, &layout, interrupt, say)?;
    if arguments.dry_run {
        let what: &str = if arguments.mode == MigrateMode::Rollback { "restore the original directory" } else { "delete the original tree" };
        run.line(format!("dry run: the command would {what} of {}; nothing was changed.", layout.root.display()).as_str());
        return Ok(0);
    }
    let refused: Option<Vec<Refusal>> = if arguments.mode == MigrateMode::Rollback { rollback(&mut run, arguments.discard_unreadable)? } else { remove_old_tree(&mut run, arguments.discard_unreadable)? };
    if let Some(refusals) = refused {
        say_refusals(run.say, refusals.as_slice());
        return Ok(REFUSED_EXIT_CODE);
    }
    return Ok(0);
}

/// What:
///  The action of `git cli-git migrate-to-subvolume`: help, or the run from the working directory's repository.
/// Why:
///   Progress goes to standard error live; the action carries only the exit status.
///
/// In TS you'd write (pseudocode):
/// ```ts
/// function planMigrate(args: MigrateArguments, cwd: string): Action;
/// ```
pub fn migrate_action(arguments: &MigrateArguments, cwd: &Path) -> Action {
    if arguments.help {
        return Action::Exit { code: 0, stdout: String::from(MIGRATE_HELP), stderr: String::new() };
    }
    let root: PathBuf = match main_checkout_root(cwd) {
        Ok(found) => found,
        Err(message) => {
            return Action::Exit {
                code: REFUSED_EXIT_CODE,
                stdout: String::new(),
                stderr: format!("git cli-git migrate-to-subvolume: refused: {message}\n  What to do: run the command inside the repository whose main checkout you want to convert.\nNothing was changed.\n"),
            };
        }
    };
    let mut say = |text: &str| {
        let mut stderr = std::io::stderr().lock();
        let _written = writeln!(stderr, "{text}");
    };
    let code: i32 = execute(&LinuxPlatform, arguments, root.as_path(), &Interrupt::never(), &mut say);
    return Action::Exit { code, stdout: String::new(), stderr: String::new() };
}

/// Command controls stay out of the release executable.
#[cfg(test)]
#[path = "subvolume_command_tests.rs"]
mod tests;