use std::{
    collections::HashMap,
    env, fs,
    io::{self, Read},
};
use yaml_rust::{Yaml, YamlLoader};

pub(super) fn run(version: super::ConfigVersion) -> Result<(), Error> {
    match version {
        super::ConfigVersion::V20240701 => migrate_20240701(),
    }
}

#[derive(thiserror::Error, Debug)]
pub(crate) enum Error {
    #[error("failed to parse the old config file (.config/default.yml)")]
    ReadOldConfig(#[from] ReadYamlConfigError),
}

#[derive(thiserror::Error, Debug)]
pub(crate) enum ReadYamlConfigError {
    #[error(transparent)]
    ReadFile(#[from] io::Error),
    #[error(transparent)]
    Yaml(#[from] yaml_rust::ScanError),
    #[error("invalid config file ({0})")]
    InvalidConfig(String),
}

fn read_default_yml() -> Result<HashMap<String, Yaml>, ReadYamlConfigError> {
    let cwd = env::current_dir()?;
    let mut default_yml = fs::File::open(cwd.join(".config/default.yml"))?;

    let mut buffer = String::new();
    default_yml.read_to_string(&mut buffer)?;

    let content = YamlLoader::load_from_str(&buffer)?;

    if content.is_empty() {
        return Err(ReadYamlConfigError::InvalidConfig(
            "file is empty".to_string(),
        ));
    }
    if content.len() > 2 || content[0].is_array() {
        return Err(ReadYamlConfigError::InvalidConfig(
            "top-level should not be an array".to_string(),
        ));
    }

    let content = content[0]
        .clone()
        .into_hash()
        .ok_or(ReadYamlConfigError::InvalidConfig(
            "invalid format".to_string(),
        ))?;

    let mut res = HashMap::new();

    for (key, val) in content {
        let Some(key) = key.as_str() else {
            return Err(ReadYamlConfigError::InvalidConfig(format!(
                "non-string key found: {:?}",
                key
            )));
        };
        res.insert(key.to_owned(), val);
    }

    Ok(res)
}

fn migrate_20240701() -> Result<(), Error> {
    let old_config = read_default_yml()?;

    for (k, v) in old_config {
        println!("{}:\n  {:?}", k, v);
    }

    Ok(())
}