zeph 0.21.1

// SPDX-FileCopyrightText: 2026 Andrei G <bug-ops>
// SPDX-License-Identifier: MIT OR Apache-2.0

use std::path::Path;

use similar::{ChangeTag, TextDiff};
use zeph_core::config::migrate::{ConfigMigrator, MIGRATIONS, MigrationResult};

/// Handle the `zeph migrate-config` command.
///
/// Applies all registered migration steps from [`MIGRATIONS`] in chronological order,
/// followed by the `ConfigMigrator` pass that adds missing keys as commented-out entries.
///
/// # Errors
///
/// Returns an error if the config file cannot be read, any migration step fails, or the
/// in-place write fails.
pub(crate) fn handle_migrate_config(
    config_path: &Path,
    in_place: bool,
    diff: bool,
) -> anyhow::Result<()> {
    let input = if config_path.exists() {
        std::fs::read_to_string(config_path)?
    } else {
        String::new()
    };

    // Apply all registered migration steps in order, collecting results for diff reporting.
    let mut current = input.clone();
    let mut step_results: Vec<(&str, MigrationResult)> = Vec::with_capacity(MIGRATIONS.len());
    for migration in MIGRATIONS.iter() {
        let result = migration.apply(&current)?;
        current.clone_from(&result.output);
        step_results.push((migration.name(), result));
    }

    // Final pass: add missing default keys as commented-out entries.
    let migrator = ConfigMigrator::new();
    let result = migrator.migrate(&current)?;

    if diff {
        print_diff(&input, &result.output);
        for (name, step_result) in &step_results {
            if step_result.changed_count > 0 {
                eprintln!(
                    "{}: {} change(s) (sections: {})",
                    name,
                    step_result.changed_count,
                    if step_result.sections_changed.is_empty() {
                        "none".to_owned()
                    } else {
                        step_result.sections_changed.join(", ")
                    }
                );
            }
        }
        eprintln!(
            "Migration would add {} entries ({} sections).",
            result.changed_count,
            result.sections_changed.len()
        );
    } else if in_place {
        atomic_write(config_path, &result.output)?;
        eprintln!(
            "Config migrated in-place: {} ({} entries added, sections: {})",
            config_path.display(),
            result.changed_count,
            if result.sections_changed.is_empty() {
                "none".to_owned()
            } else {
                result.sections_changed.join(", ")
            }
        );
    } else {
        print!("{}", result.output);
    }

    Ok(())
}

/// Print a unified-style diff between `old` and `new`.
fn print_diff(old: &str, new: &str) {
    let diff = TextDiff::from_lines(old, new);
    for change in diff.iter_all_changes() {
        match change.tag() {
            ChangeTag::Equal => print!(" {change}"),
            ChangeTag::Insert => print!("+{change}"),
            ChangeTag::Delete => print!("-{change}"),
        }
    }
}

/// Write `content` to `path` atomically using a temporary file in the same directory,
/// preserving the original file's permissions before renaming into place.
fn atomic_write(path: &Path, content: &str) -> anyhow::Result<()> {
    use std::io::Write;

    let original_perms = if path.exists() {
        Some(std::fs::metadata(path)?.permissions())
    } else {
        None
    };

    let parent = path.parent().unwrap_or_else(|| Path::new("."));
    let mut tmp = tempfile::NamedTempFile::new_in(parent)?;
    tmp.write_all(content.as_bytes())?;
    tmp.flush()?;
    tmp.as_file().sync_all()?;

    if let Some(perms) = original_perms {
        std::fs::set_permissions(tmp.path(), perms)?;
    }

    tmp.persist(path)?;

    Ok(())
}