git-perf 0.20.0

use anyhow::Result;
use config::{Config, ConfigError, File, FileFormat};
use std::{
    env,
    fs::File as StdFile,
    io::{Read, Write},
    path::{Path, PathBuf},
};
use toml_edit::{value, DocumentMut, Item, Table};

use crate::defaults;
use crate::git::git_interop::{get_head_revision, get_repository_root};

// Import the CLI types for dispersion method
use git_perf_cli_types::DispersionMethod;

/// Extension trait to get values with parent table fallback.
///
/// This provides a consistent way to retrieve a value for a given logical name
/// and fall back to the parent table when the specific name is not present.
pub trait ConfigParentFallbackExt {
    /// Returns a string value for `{parent}.{name}.{key}` if available.
    /// Otherwise falls back to `{parent}.{key}` (parent table defaults).
    ///
    /// The `parent` is the parent table name (e.g., "measurement").
    /// The `name` is the specific identifier within that parent.
    fn get_with_parent_fallback(&self, parent: &str, name: &str, key: &str) -> Option<String>;
}

impl ConfigParentFallbackExt for Config {
    fn get_with_parent_fallback(&self, parent: &str, name: &str, key: &str) -> Option<String> {
        // Try specific measurement first: parent.name.key
        let specific_key = format!("{}.{}.{}", parent, name, key);
        if let Ok(v) = self.get_string(&specific_key) {
            return Some(v);
        }

        // Fallback to parent table: parent.key
        let parent_key = format!("{}.{}", parent, key);
        if let Ok(v) = self.get_string(&parent_key) {
            return Some(v);
        }

        None
    }
}

/// Get the main repository config path (always in repo root)
fn get_main_config_path() -> Result<PathBuf> {
    // Use git to find the repository root
    let repo_root = get_repository_root().map_err(|e| {
        anyhow::anyhow!(
            "Failed to determine repository root - must be run from within a git repository: {}",
            e
        )
    })?;

    if repo_root.is_empty() {
        return Err(anyhow::anyhow!(
            "Repository root is empty - must be run from within a git repository"
        ));
    }

    Ok(PathBuf::from(repo_root).join(".gitperfconfig"))
}

/// Write config to the main repository directory (always in repo root)
pub fn write_config(conf: &str) -> Result<()> {
    let path = get_main_config_path()?;
    let mut f = StdFile::create(path)?;
    f.write_all(conf.as_bytes())?;
    Ok(())
}

/// Read hierarchical configuration (system -> local override)
pub fn read_hierarchical_config() -> Result<Config, ConfigError> {
    let mut builder = Config::builder();

    // 1. System-wide config (XDG_CONFIG_HOME or ~/.config/git-perf/config.toml)
    if let Ok(xdg_config_home) = env::var("XDG_CONFIG_HOME") {
        let system_config_path = Path::new(&xdg_config_home)
            .join("git-perf")
            .join("config.toml");
        builder = builder.add_source(
            File::from(system_config_path)
                .format(FileFormat::Toml)
                .required(false),
        );
    } else if let Some(home) = dirs_next::home_dir() {
        let system_config_path = home.join(".config").join("git-perf").join("config.toml");
        builder = builder.add_source(
            File::from(system_config_path)
                .format(FileFormat::Toml)
                .required(false),
        );
    }

    // 2. Local config (repository .gitperfconfig) - this overrides system config
    if let Some(local_path) = find_config_path() {
        builder = builder.add_source(
            File::from(local_path)
                .format(FileFormat::Toml)
                .required(false),
        );
    }

    builder.build()
}

fn find_config_path() -> Option<PathBuf> {
    // Use get_main_config_path but handle errors gracefully
    let path = get_main_config_path().ok()?;
    if path.is_file() {
        Some(path)
    } else {
        None
    }
}

fn read_config_from_file<P: AsRef<Path>>(file: P) -> Result<String> {
    let mut conf_str = String::new();
    StdFile::open(file)?.read_to_string(&mut conf_str)?;
    Ok(conf_str)
}

#[must_use]
pub fn determine_epoch_from_config(measurement: &str) -> Option<u32> {
    let config = read_hierarchical_config()
        .map_err(|e| {
            // Log the error but don't fail - this is expected when no config exists
            log::debug!("Could not read hierarchical config: {}", e);
        })
        .ok()?;

    // Use parent fallback for measurement epoch
    config
        .get_with_parent_fallback("measurement", measurement, "epoch")
        .and_then(|s| u32::from_str_radix(&s, 16).ok())
}

pub fn bump_epoch_in_conf(measurement: &str, conf_str: &mut String) -> Result<()> {
    let mut conf = conf_str
        .parse::<DocumentMut>()
        .map_err(|e| anyhow::anyhow!("Failed to parse config: {}", e))?;

    let head_revision = get_head_revision()?;

    // Ensure that non-inline tables are written in an empty config file
    if !conf.contains_key("measurement") {
        conf["measurement"] = Item::Table(Table::new());
    }
    if !conf["measurement"]
        .as_table()
        .unwrap()
        .contains_key(measurement)
    {
        conf["measurement"][measurement] = Item::Table(Table::new());
    }

    conf["measurement"][measurement]["epoch"] = value(&head_revision[0..8]);
    *conf_str = conf.to_string();

    Ok(())
}

pub fn bump_epoch(measurement: &str) -> Result<()> {
    // Read existing config from the main config path
    let config_path = get_main_config_path()?;
    let mut conf_str = read_config_from_file(&config_path).unwrap_or_default();

    bump_epoch_in_conf(measurement, &mut conf_str)?;
    write_config(&conf_str)?;
    Ok(())
}

/// Returns the backoff max elapsed seconds from config, or the default if not set.
#[must_use]
pub fn backoff_max_elapsed_seconds() -> u64 {
    match read_hierarchical_config() {
        Ok(config) => {
            if let Ok(seconds) = config.get_int("backoff.max_elapsed_seconds") {
                seconds as u64
            } else {
                defaults::DEFAULT_BACKOFF_MAX_ELAPSED_SECONDS
            }
        }
        Err(_) => defaults::DEFAULT_BACKOFF_MAX_ELAPSED_SECONDS,
    }
}

/// Returns the minimum relative deviation threshold from config, or None if not set.
#[must_use]
pub fn audit_min_relative_deviation(measurement: &str) -> Option<f64> {
    let config = read_hierarchical_config().ok()?;

    if let Some(s) =
        config.get_with_parent_fallback("measurement", measurement, "min_relative_deviation")
    {
        if let Ok(v) = s.parse::<f64>() {
            return Some(v);
        }
    }

    None
}

/// Returns the minimum absolute deviation threshold from config, or None if not set.
#[must_use]
pub fn audit_min_absolute_deviation(measurement: &str) -> Option<f64> {
    let config = read_hierarchical_config().ok()?;

    if let Some(s) =
        config.get_with_parent_fallback("measurement", measurement, "min_absolute_deviation")
    {
        if let Ok(v) = s.parse::<f64>() {
            return Some(v);
        }
    }

    None
}

/// Returns the dispersion method from config, or StandardDeviation if not set.
#[must_use]
pub fn audit_dispersion_method(measurement: &str) -> DispersionMethod {
    let Some(config) = read_hierarchical_config().ok() else {
        return DispersionMethod::StandardDeviation;
    };

    if let Some(s) =
        config.get_with_parent_fallback("measurement", measurement, "dispersion_method")
    {
        if let Ok(method) = s.parse::<DispersionMethod>() {
            return method;
        }
    }

    DispersionMethod::StandardDeviation
}

/// Returns the minimum measurements from config, or None if not set.
#[must_use]
pub fn audit_min_measurements(measurement: &str) -> Option<u16> {
    let config = read_hierarchical_config().ok()?;

    if let Some(s) = config.get_with_parent_fallback("measurement", measurement, "min_measurements")
    {
        if let Ok(v) = s.parse::<u16>() {
            return Some(v);
        }
    }

    None
}

/// Returns the aggregate-by reduction function from config, or None if not set.
#[must_use]
pub fn audit_aggregate_by(measurement: &str) -> Option<git_perf_cli_types::ReductionFunc> {
    let config = read_hierarchical_config().ok()?;

    let s = config.get_with_parent_fallback("measurement", measurement, "aggregate_by")?;

    // Parse the string to ReductionFunc
    match s.to_lowercase().as_str() {
        "min" => Some(git_perf_cli_types::ReductionFunc::Min),
        "max" => Some(git_perf_cli_types::ReductionFunc::Max),
        "median" => Some(git_perf_cli_types::ReductionFunc::Median),
        "mean" => Some(git_perf_cli_types::ReductionFunc::Mean),
        _ => None,
    }
}

/// Returns the sigma value from config, or None if not set.
#[must_use]
pub fn audit_sigma(measurement: &str) -> Option<f64> {
    let config = read_hierarchical_config().ok()?;

    if let Some(s) = config.get_with_parent_fallback("measurement", measurement, "sigma") {
        if let Ok(v) = s.parse::<f64>() {
            return Some(v);
        }
    }

    None
}

/// Returns the configured unit for a measurement, or None if not set.
#[must_use]
pub fn measurement_unit(measurement: &str) -> Option<String> {
    let config = read_hierarchical_config().ok()?;
    config.get_with_parent_fallback("measurement", measurement, "unit")
}

/// Returns the report template path from config, or None if not set.
#[must_use]
pub fn report_template_path() -> Option<PathBuf> {
    let config = read_hierarchical_config().ok()?;
    let path_str = config.get_string("report.template_path").ok()?;
    Some(PathBuf::from(path_str))
}

/// Returns the report custom CSS path from config, or None if not set.
#[must_use]
pub fn report_custom_css_path() -> Option<PathBuf> {
    let config = read_hierarchical_config().ok()?;
    let path_str = config.get_string("report.custom_css_path").ok()?;
    Some(PathBuf::from(path_str))
}

/// Returns the report title from config, or None if not set.
#[must_use]
pub fn report_title() -> Option<String> {
    let config = read_hierarchical_config().ok()?;
    config.get_string("report.title").ok()
}

/// Returns the change point configuration for a measurement, applying fallback rules.
///
/// Configuration keys under `[change_point]` or `[change_point."measurement_name"]`:
/// - `enabled`: Enable/disable change point detection (default: true)
/// - `min_data_points`: Minimum data points required (default: 10)
/// - `min_magnitude_pct`: Minimum percentage change to consider significant (default: 5.0)
/// - `confidence_threshold`: Minimum confidence to report a change point (0.0-1.0, default: 0.75)
/// - `penalty`: Penalty factor for PELT algorithm (default: 0.5, lower = more sensitive)
#[must_use]
pub fn change_point_config(measurement: &str) -> crate::change_point::ChangePointConfig {
    let mut config = crate::change_point::ChangePointConfig::default();

    let Ok(file_config) = read_hierarchical_config() else {
        return config;
    };

    // Check if change point detection is disabled globally or per-measurement
    if let Some(enabled_str) =
        file_config.get_with_parent_fallback("change_point", measurement, "enabled")
    {
        if let Ok(enabled) = enabled_str.parse::<bool>() {
            config.enabled = enabled;
        }
    }

    // min_data_points
    if let Some(s) =
        file_config.get_with_parent_fallback("change_point", measurement, "min_data_points")
    {
        if let Ok(v) = s.parse::<usize>() {
            config.min_data_points = v;
        }
    }

    // min_magnitude_pct
    if let Some(s) =
        file_config.get_with_parent_fallback("change_point", measurement, "min_magnitude_pct")
    {
        if let Ok(v) = s.parse::<f64>() {
            config.min_magnitude_pct = v;
        }
    }

    // confidence_threshold
    if let Some(s) =
        file_config.get_with_parent_fallback("change_point", measurement, "confidence_threshold")
    {
        if let Ok(v) = s.parse::<f64>() {
            config.confidence_threshold = v;
        }
    }

    // penalty
    if let Some(s) = file_config.get_with_parent_fallback("change_point", measurement, "penalty") {
        if let Ok(v) = s.parse::<f64>() {
            config.penalty = v;
        }
    }

    config
}

#[cfg(test)]
mod test {
    use super::*;
    use crate::test_helpers::{
        hermetic_git_env, init_repo, init_repo_with_file, with_isolated_home,
    };
    use std::fs;
    use tempfile::TempDir;

    /// Create a HOME config directory structure and return the config path
    fn create_home_config_dir(home_dir: &Path) -> PathBuf {
        let config_dir = home_dir.join(".config").join("git-perf");
        fs::create_dir_all(&config_dir).unwrap();
        config_dir.join("config.toml")
    }

    #[test]
    fn test_read_epochs() {
        with_isolated_home(|temp_dir| {
            // Create a git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create workspace config with epochs
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            let configfile = r#"[measurement]
# General performance regression
epoch="12344555"

[measurement."something"]
#My comment
epoch="34567898"

[measurement."somethingelse"]
epoch="a3dead"
"#;
            fs::write(&workspace_config_path, configfile).unwrap();

            let epoch = determine_epoch_from_config("something");
            assert_eq!(epoch, Some(0x34567898));

            let epoch = determine_epoch_from_config("somethingelse");
            assert_eq!(epoch, Some(0xa3dead));

            let epoch = determine_epoch_from_config("unspecified");
            assert_eq!(epoch, Some(0x12344555));
        });
    }

    #[test]
    fn test_bump_epochs() {
        with_isolated_home(|temp_dir| {
            // Create a temporary git repository for this test
            env::set_current_dir(temp_dir).unwrap();

            // Set up hermetic git environment
            hermetic_git_env();

            // Initialize git repository with initial commit
            init_repo_with_file(temp_dir);

            let configfile = r#"[measurement."something"]
#My comment
epoch = "34567898"
"#;

            let mut actual = String::from(configfile);
            bump_epoch_in_conf("something", &mut actual).expect("Failed to bump epoch");

            let expected = format!(
                r#"[measurement."something"]
#My comment
epoch = "{}"
"#,
                &get_head_revision().expect("get_head_revision failed")[0..8],
            );

            assert_eq!(actual, expected);
        });
    }

    #[test]
    fn test_bump_new_epoch_and_read_it() {
        with_isolated_home(|temp_dir| {
            // Create a temporary git repository for this test
            env::set_current_dir(temp_dir).unwrap();

            // Set up hermetic git environment
            hermetic_git_env();

            // Initialize git repository with initial commit
            init_repo_with_file(temp_dir);

            let mut conf = String::new();
            bump_epoch_in_conf("mymeasurement", &mut conf).expect("Failed to bump epoch");

            // Write the config to a file and test reading it
            let config_path = temp_dir.join(".gitperfconfig");
            fs::write(&config_path, &conf).unwrap();

            let epoch = determine_epoch_from_config("mymeasurement");
            assert!(epoch.is_some());
        });
    }

    #[test]
    fn test_backoff_max_elapsed_seconds() {
        with_isolated_home(|temp_dir| {
            // Create git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create workspace config with explicit value
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            let local_config = "[backoff]\nmax_elapsed_seconds = 42\n";
            fs::write(&workspace_config_path, local_config).unwrap();

            // Test with explicit value
            assert_eq!(super::backoff_max_elapsed_seconds(), 42);

            // Remove config file and test default
            fs::remove_file(&workspace_config_path).unwrap();
            assert_eq!(super::backoff_max_elapsed_seconds(), 60);
        });
    }

    #[test]
    fn test_audit_min_relative_deviation() {
        with_isolated_home(|temp_dir| {
            // Create git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create workspace config with measurement-specific settings
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            let local_config = r#"
[measurement]
min_relative_deviation = 5.0

[measurement."build_time"]
min_relative_deviation = 10.0

[measurement."memory_usage"]
min_relative_deviation = 2.5
"#;
            fs::write(&workspace_config_path, local_config).unwrap();

            // Test measurement-specific settings
            assert_eq!(
                super::audit_min_relative_deviation("build_time"),
                Some(10.0)
            );
            assert_eq!(
                super::audit_min_relative_deviation("memory_usage"),
                Some(2.5)
            );
            assert_eq!(
                super::audit_min_relative_deviation("other_measurement"),
                Some(5.0) // Now falls back to parent table
            );

            // Test global (now parent table) setting
            let global_config = r#"
[measurement]
min_relative_deviation = 5.0
"#;
            fs::write(&workspace_config_path, global_config).unwrap();
            assert_eq!(
                super::audit_min_relative_deviation("any_measurement"),
                Some(5.0)
            );

            // Test precedence - measurement-specific overrides global
            let precedence_config = r#"
[measurement]
min_relative_deviation = 5.0

[measurement."build_time"]
min_relative_deviation = 10.0
"#;
            fs::write(&workspace_config_path, precedence_config).unwrap();
            assert_eq!(
                super::audit_min_relative_deviation("build_time"),
                Some(10.0)
            );
            assert_eq!(
                super::audit_min_relative_deviation("other_measurement"),
                Some(5.0)
            );

            // Test no config
            fs::remove_file(&workspace_config_path).unwrap();
            assert_eq!(super::audit_min_relative_deviation("any_measurement"), None);
        });
    }

    #[test]
    fn test_audit_min_absolute_deviation() {
        with_isolated_home(|temp_dir| {
            // Create git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create workspace config with measurement-specific settings
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            let local_config = r#"
[measurement]
min_absolute_deviation = 5.0

[measurement."build_time"]
min_absolute_deviation = 10.0

[measurement."memory_usage"]
min_absolute_deviation = 2.5
"#;
            fs::write(&workspace_config_path, local_config).unwrap();

            // Test measurement-specific settings
            assert_eq!(
                super::audit_min_absolute_deviation("build_time"),
                Some(10.0)
            );
            assert_eq!(
                super::audit_min_absolute_deviation("memory_usage"),
                Some(2.5)
            );
            assert_eq!(
                super::audit_min_absolute_deviation("other_measurement"),
                Some(5.0) // falls back to parent table
            );

            // Test global (parent table) setting
            let global_config = r#"
[measurement]
min_absolute_deviation = 5.0
"#;
            fs::write(&workspace_config_path, global_config).unwrap();
            assert_eq!(
                super::audit_min_absolute_deviation("any_measurement"),
                Some(5.0)
            );

            // Test precedence - measurement-specific overrides global
            let precedence_config = r#"
[measurement]
min_absolute_deviation = 5.0

[measurement."build_time"]
min_absolute_deviation = 10.0
"#;
            fs::write(&workspace_config_path, precedence_config).unwrap();
            assert_eq!(
                super::audit_min_absolute_deviation("build_time"),
                Some(10.0)
            );
            assert_eq!(
                super::audit_min_absolute_deviation("other_measurement"),
                Some(5.0)
            );

            // Test no config
            fs::remove_file(&workspace_config_path).unwrap();
            assert_eq!(super::audit_min_absolute_deviation("any_measurement"), None);
        });
    }

    #[test]
    fn test_audit_dispersion_method() {
        with_isolated_home(|temp_dir| {
            // Create git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create workspace config with measurement-specific settings
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            let local_config = r#"
[measurement]
dispersion_method = "stddev"

[measurement."build_time"]
dispersion_method = "mad"

[measurement."memory_usage"]
dispersion_method = "stddev"
"#;
            fs::write(&workspace_config_path, local_config).unwrap();

            // Test measurement-specific settings
            assert_eq!(
                super::audit_dispersion_method("build_time"),
                git_perf_cli_types::DispersionMethod::MedianAbsoluteDeviation
            );
            assert_eq!(
                super::audit_dispersion_method("memory_usage"),
                git_perf_cli_types::DispersionMethod::StandardDeviation
            );
            assert_eq!(
                super::audit_dispersion_method("other_measurement"),
                git_perf_cli_types::DispersionMethod::StandardDeviation
            );

            // Test global (now parent table) setting
            let global_config = r#"
[measurement]
dispersion_method = "mad"
"#;
            fs::write(&workspace_config_path, global_config).unwrap();
            assert_eq!(
                super::audit_dispersion_method("any_measurement"),
                git_perf_cli_types::DispersionMethod::MedianAbsoluteDeviation
            );

            // Test precedence - measurement-specific overrides global
            let precedence_config = r#"
[measurement]
dispersion_method = "mad"

[measurement."build_time"]
dispersion_method = "stddev"
"#;
            fs::write(&workspace_config_path, precedence_config).unwrap();
            assert_eq!(
                super::audit_dispersion_method("build_time"),
                git_perf_cli_types::DispersionMethod::StandardDeviation
            );
            assert_eq!(
                super::audit_dispersion_method("other_measurement"),
                git_perf_cli_types::DispersionMethod::MedianAbsoluteDeviation
            );

            // Test no config (should return StandardDeviation)
            fs::remove_file(&workspace_config_path).unwrap();
            assert_eq!(
                super::audit_dispersion_method("any_measurement"),
                git_perf_cli_types::DispersionMethod::StandardDeviation
            );
        });
    }

    #[test]
    fn test_bump_epoch_in_conf_creates_proper_tables() {
        // We need to test the production bump_epoch_in_conf function, but it calls get_head_revision()
        // which requires a git repo. Let's temporarily modify the environment to make it work.
        with_isolated_home(|temp_dir| {
            env::set_current_dir(temp_dir).unwrap();

            // Set up minimal git environment
            hermetic_git_env();

            init_repo_with_file(temp_dir);

            // Test case 1: Empty config string should create proper table structure
            let mut empty_config = String::new();

            // This calls the actual production function!
            bump_epoch_in_conf("mymeasurement", &mut empty_config).unwrap();

            // Verify that proper table structure is created (not inline tables)
            assert!(empty_config.contains("[measurement]"));
            assert!(empty_config.contains("[measurement.mymeasurement]"));
            assert!(empty_config.contains("epoch ="));
            // Ensure it's NOT using inline table syntax
            assert!(!empty_config.contains("measurement = {"));
            assert!(!empty_config.contains("mymeasurement = {"));

            // Test case 2: Existing config should preserve structure and add new measurement
            let mut existing_config = r#"[measurement]
existing_setting = "value"

[measurement."other"]
epoch = "oldvalue"
"#
            .to_string();

            bump_epoch_in_conf("newmeasurement", &mut existing_config).unwrap();

            // Verify it maintains existing structure and adds new measurement with proper table format
            assert!(existing_config.contains("[measurement.newmeasurement]"));
            assert!(existing_config.contains("existing_setting = \"value\""));
            assert!(existing_config.contains("[measurement.\"other\"]"));
            assert!(!existing_config.contains("newmeasurement = {"));
        });
    }

    #[test]
    fn test_find_config_path_in_git_root() {
        with_isolated_home(|temp_dir| {
            // Create a git repository
            env::set_current_dir(temp_dir).unwrap();

            // Initialize git repository
            init_repo(temp_dir);

            // Create config in git root
            let config_path = temp_dir.join(".gitperfconfig");
            fs::write(
                &config_path,
                "[measurement.\"test\"]\nepoch = \"12345678\"\n",
            )
            .unwrap();

            // Test that find_config_path finds it
            let found_path = find_config_path();
            assert!(found_path.is_some());
            // Canonicalize both paths to handle symlinks (e.g., /var -> /private/var on macOS)
            assert_eq!(
                found_path.unwrap().canonicalize().unwrap(),
                config_path.canonicalize().unwrap()
            );
        });
    }

    #[test]
    fn test_find_config_path_not_found() {
        with_isolated_home(|temp_dir| {
            // Create a git repository but no .gitperfconfig
            env::set_current_dir(temp_dir).unwrap();

            // Initialize git repository
            init_repo(temp_dir);

            // Test that find_config_path returns None when no .gitperfconfig exists
            let found_path = find_config_path();
            assert!(found_path.is_none());
        });
    }

    #[test]
    fn test_hierarchical_config_workspace_overrides_home() {
        with_isolated_home(|temp_dir| {
            // Create a git repository
            env::set_current_dir(temp_dir).unwrap();

            // Initialize git repository
            init_repo(temp_dir);

            // Create home config
            let home_config_path = create_home_config_dir(temp_dir);
            fs::write(
                &home_config_path,
                r#"
[measurement."test"]
backoff_max_elapsed_seconds = 30
audit_min_relative_deviation = 1.0
"#,
            )
            .unwrap();

            // Create workspace config that overrides some values
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            fs::write(
                &workspace_config_path,
                r#"
[measurement."test"]
backoff_max_elapsed_seconds = 60
"#,
            )
            .unwrap();

            // Set HOME to our temp directory
            env::set_var("HOME", temp_dir);
            env::remove_var("XDG_CONFIG_HOME");

            // Read hierarchical config and verify workspace overrides home
            let config = read_hierarchical_config().unwrap();

            // backoff_max_elapsed_seconds should be overridden by workspace config
            let backoff: i32 = config
                .get("measurement.test.backoff_max_elapsed_seconds")
                .unwrap();
            assert_eq!(backoff, 60);

            // audit_min_relative_deviation should come from home config
            let deviation: f64 = config
                .get("measurement.test.audit_min_relative_deviation")
                .unwrap();
            assert_eq!(deviation, 1.0);
        });
    }

    #[test]
    fn test_determine_epoch_from_config_with_missing_file() {
        // Test that missing config file doesn't panic and returns None
        let temp_dir = TempDir::new().unwrap();
        fs::create_dir_all(temp_dir.path()).unwrap();
        env::set_current_dir(temp_dir.path()).unwrap();

        let epoch = determine_epoch_from_config("test_measurement");
        assert!(epoch.is_none());
    }

    #[test]
    fn test_determine_epoch_from_config_with_invalid_toml() {
        let temp_dir = TempDir::new().unwrap();
        let config_path = temp_dir.path().join(".gitperfconfig");
        fs::write(&config_path, "invalid toml content").unwrap();

        fs::create_dir_all(temp_dir.path()).unwrap();
        env::set_current_dir(temp_dir.path()).unwrap();

        let epoch = determine_epoch_from_config("test_measurement");
        assert!(epoch.is_none());
    }

    #[test]
    fn test_write_config_creates_file() {
        with_isolated_home(|temp_dir| {
            // Create git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create a subdirectory to test that config is written to repo root
            let subdir = temp_dir.join("a").join("b").join("c");
            fs::create_dir_all(&subdir).unwrap();
            env::set_current_dir(&subdir).unwrap();

            let config_content = "[measurement.\"test\"]\nepoch = \"12345678\"\n";
            write_config(config_content).unwrap();

            // Config should be written to repo root, not subdirectory
            let repo_config_path = temp_dir.join(".gitperfconfig");
            let subdir_config_path = subdir.join(".gitperfconfig");

            assert!(repo_config_path.is_file());
            assert!(!subdir_config_path.is_file());

            let content = fs::read_to_string(&repo_config_path).unwrap();
            assert_eq!(content, config_content);
        });
    }

    #[test]
    fn test_hierarchical_config_system_override() {
        with_isolated_home(|temp_dir| {
            // Create system config (home directory config)
            let system_config_path = create_home_config_dir(temp_dir);
            let system_config = r#"
[measurement]
min_relative_deviation = 5.0
dispersion_method = "mad"

[backoff]
max_elapsed_seconds = 120
"#;
            fs::write(&system_config_path, system_config).unwrap();

            // Create git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create workspace config that overrides system config
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            let local_config = r#"
[measurement]
min_relative_deviation = 10.0

[measurement."build_time"]
min_relative_deviation = 15.0
dispersion_method = "stddev"
"#;
            fs::write(&workspace_config_path, local_config).unwrap();

            // Test hierarchical config reading
            let config = read_hierarchical_config().unwrap();

            // Test that local parent table overrides system config via helper
            use super::ConfigParentFallbackExt;
            assert_eq!(
                config
                    .get_with_parent_fallback(
                        "measurement",
                        "any_measurement",
                        "min_relative_deviation"
                    )
                    .unwrap()
                    .parse::<f64>()
                    .unwrap(),
                10.0
            );
            assert_eq!(
                config
                    .get_with_parent_fallback("measurement", "any_measurement", "dispersion_method")
                    .unwrap(),
                "mad"
            ); // Not overridden in local for parent fallback

            // Test measurement-specific override
            assert_eq!(
                config
                    .get_float("measurement.build_time.min_relative_deviation")
                    .unwrap(),
                15.0
            );
            assert_eq!(
                config
                    .get_string("measurement.build_time.dispersion_method")
                    .unwrap(),
                "stddev"
            );

            // Test that system config is still available for non-overridden values
            assert_eq!(config.get_int("backoff.max_elapsed_seconds").unwrap(), 120);

            // Test the convenience functions
            assert_eq!(audit_min_relative_deviation("build_time"), Some(15.0));
            assert_eq!(
                audit_min_relative_deviation("other_measurement"),
                Some(10.0)
            );
            assert_eq!(
                audit_dispersion_method("build_time"),
                git_perf_cli_types::DispersionMethod::StandardDeviation
            );
            assert_eq!(
                audit_dispersion_method("other_measurement"),
                git_perf_cli_types::DispersionMethod::MedianAbsoluteDeviation
            );
            assert_eq!(backoff_max_elapsed_seconds(), 120);
        });
    }

    #[test]
    fn test_read_config_from_file_missing_file() {
        let temp_dir = TempDir::new().unwrap();
        let nonexistent_file = temp_dir.path().join("does_not_exist.toml");

        // Should return error, not Ok(String::new())
        let result = read_config_from_file(&nonexistent_file);
        assert!(result.is_err());
    }

    #[test]
    fn test_read_config_from_file_valid_content() {
        let temp_dir = TempDir::new().unwrap();
        let config_file = temp_dir.path().join("test_config.toml");
        let expected_content = "[measurement]\nepoch = \"12345678\"\n";

        fs::write(&config_file, expected_content).unwrap();

        let result = read_config_from_file(&config_file);
        assert!(result.is_ok());
        let content = result.unwrap();
        assert_eq!(content, expected_content);

        // This would catch the mutant that returns Ok(String::new())
        assert!(!content.is_empty());
    }

    #[test]
    fn test_audit_min_measurements() {
        with_isolated_home(|temp_dir| {
            // Create git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create workspace config with measurement-specific settings
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            let local_config = r#"
[measurement]
min_measurements = 5

[measurement."build_time"]
min_measurements = 10

[measurement."memory_usage"]
min_measurements = 3
"#;
            fs::write(&workspace_config_path, local_config).unwrap();

            // Test measurement-specific settings
            assert_eq!(super::audit_min_measurements("build_time"), Some(10));
            assert_eq!(super::audit_min_measurements("memory_usage"), Some(3));
            assert_eq!(super::audit_min_measurements("other_measurement"), Some(5));

            // Test no config
            fs::remove_file(&workspace_config_path).unwrap();
            assert_eq!(super::audit_min_measurements("any_measurement"), None);
        });
    }

    #[test]
    fn test_audit_aggregate_by() {
        with_isolated_home(|temp_dir| {
            // Create git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create workspace config with measurement-specific settings
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            let local_config = r#"
[measurement]
aggregate_by = "median"

[measurement."build_time"]
aggregate_by = "max"

[measurement."memory_usage"]
aggregate_by = "mean"
"#;
            fs::write(&workspace_config_path, local_config).unwrap();

            // Test measurement-specific settings
            assert_eq!(
                super::audit_aggregate_by("build_time"),
                Some(git_perf_cli_types::ReductionFunc::Max)
            );
            assert_eq!(
                super::audit_aggregate_by("memory_usage"),
                Some(git_perf_cli_types::ReductionFunc::Mean)
            );
            assert_eq!(
                super::audit_aggregate_by("other_measurement"),
                Some(git_perf_cli_types::ReductionFunc::Median)
            );

            // Test no config
            fs::remove_file(&workspace_config_path).unwrap();
            assert_eq!(super::audit_aggregate_by("any_measurement"), None);
        });
    }

    #[test]
    fn test_audit_sigma() {
        with_isolated_home(|temp_dir| {
            // Create git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create workspace config with measurement-specific settings
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            let local_config = r#"
[measurement]
sigma = 3.0

[measurement."build_time"]
sigma = 5.5

[measurement."memory_usage"]
sigma = 2.0
"#;
            fs::write(&workspace_config_path, local_config).unwrap();

            // Test measurement-specific settings
            assert_eq!(super::audit_sigma("build_time"), Some(5.5));
            assert_eq!(super::audit_sigma("memory_usage"), Some(2.0));
            assert_eq!(super::audit_sigma("other_measurement"), Some(3.0));

            // Test no config
            fs::remove_file(&workspace_config_path).unwrap();
            assert_eq!(super::audit_sigma("any_measurement"), None);
        });
    }

    #[test]
    fn test_measurement_unit() {
        with_isolated_home(|temp_dir| {
            // Create git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create workspace config with measurement-specific units
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            let local_config = r#"
[measurement]
unit = "ms"

[measurement."build_time"]
unit = "ms"

[measurement."memory_usage"]
unit = "bytes"

[measurement."throughput"]
unit = "requests/sec"
"#;
            fs::write(&workspace_config_path, local_config).unwrap();

            // Test measurement-specific settings
            assert_eq!(
                super::measurement_unit("build_time"),
                Some("ms".to_string())
            );
            assert_eq!(
                super::measurement_unit("memory_usage"),
                Some("bytes".to_string())
            );
            assert_eq!(
                super::measurement_unit("throughput"),
                Some("requests/sec".to_string())
            );

            // Test fallback to parent table default
            assert_eq!(
                super::measurement_unit("other_measurement"),
                Some("ms".to_string())
            );

            // Test no config
            fs::remove_file(&workspace_config_path).unwrap();
            assert_eq!(super::measurement_unit("any_measurement"), None);
        });
    }

    #[test]
    fn test_measurement_unit_precedence() {
        with_isolated_home(|temp_dir| {
            // Create git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create workspace config testing precedence
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            let precedence_config = r#"
[measurement]
unit = "ms"

[measurement."build_time"]
unit = "seconds"
"#;
            fs::write(&workspace_config_path, precedence_config).unwrap();

            // Measurement-specific should override parent default
            assert_eq!(
                super::measurement_unit("build_time"),
                Some("seconds".to_string())
            );

            // Other measurements should use parent default
            assert_eq!(
                super::measurement_unit("other_measurement"),
                Some("ms".to_string())
            );
        });
    }

    #[test]
    fn test_measurement_unit_no_parent_default() {
        with_isolated_home(|temp_dir| {
            // Create git repository
            env::set_current_dir(temp_dir).unwrap();
            init_repo(temp_dir);

            // Create workspace config with only measurement-specific units (no parent default)
            let workspace_config_path = temp_dir.join(".gitperfconfig");
            let local_config = r#"
[measurement."build_time"]
unit = "ms"

[measurement."memory_usage"]
unit = "bytes"
"#;
            fs::write(&workspace_config_path, local_config).unwrap();

            // Test measurement-specific settings
            assert_eq!(
                super::measurement_unit("build_time"),
                Some("ms".to_string())
            );
            assert_eq!(
                super::measurement_unit("memory_usage"),
                Some("bytes".to_string())
            );

            // Test measurement without unit (no parent default either)
            assert_eq!(super::measurement_unit("other_measurement"), None);
        });
    }
}