use anyhow::{anyhow, bail, Context, Result};
use serde::{de::DeserializeOwned, Serialize};
use serde_yaml::{Mapping, Value};
use std::{fs, path::PathBuf};

/// read data from yaml as struct T
pub fn read_yaml<T: DeserializeOwned>(path: &PathBuf) -> Result<T> {
    if !path.exists() {
        bail!("file not found \"{}\"", path.display());
    }

    let yaml_str = fs::read_to_string(&path)
        .context(format!("failed to read the file \"{}\"", path.display()))?;

    serde_yaml::from_str::<T>(&yaml_str).context(format!(
        "failed to read the file with yaml format \"{}\"",
        path.display()
    ))
}

/// read mapping from yaml fix #165
pub fn read_merge_mapping(path: &PathBuf) -> Result<Mapping> {
    let mut val: Value = read_yaml(path)?;
    val.apply_merge()
        .context(format!("failed to apply merge \"{}\"", path.display()))?;

    Ok(val
        .as_mapping()
        .ok_or(anyhow!(
            "failed to transform to yaml mapping \"{}\"",
            path.display()
        ))?
        .to_owned())
}

/// save the data to the file
/// can set `prefix` string to add some comments
pub fn save_yaml<T: Serialize>(path: PathBuf, data: &T, prefix: Option<&str>) -> Result<()> {
    let data_str = serde_yaml::to_string(data)?;

    let yaml_str = match prefix {
        Some(prefix) => format!("{prefix}\n{data_str}"),
        None => data_str,
    };

    let path_str = path.as_os_str().to_string_lossy().to_string();
    fs::write(path, yaml_str.as_bytes()).context(format!("failed to save file \"{path_str}\""))
}