use super::{Error, PathBuf, File, Read, Write};
/// # Usage:
/// ```
/// use std::path::PathBuf;
/// use csv_challenge::load_csv;
/// let filename = PathBuf::from(r"F:\Rust_Practise\csv_challenge\src\input\challenge.csv");
/// let csv_data = load_csv(filename);
/// assert!(csv_data.is_ok());
///```
pub fn load_csv(csv_file:PathBuf) ->Result<String,Error> {
   let csv_data =  read(csv_file)?;
   Ok(csv_data)
}
/// # Usage:
/// ```ignore
/// 
/// let filename = PathBuf::from(r"F:\Rust_Practise\csv_challenge\src\input\challenge.csv");
/// let csv_data = load_csv(filename).unwrap();
/// let modified_data = replace_column(csv_data, "City", "Beijing").unwrap();
/// let output_file = write_csv(&modified_data, "output/test.csv");
/// assert!(output_file.is_ok());
/// 
pub fn write_csv(csv_data:&str,filename:&str) -> Result<(),Error> {
    write(csv_data, filename)?;
    Ok(())
}

fn read(path:PathBuf) -> Result<String,Error> {
    let mut csv_data=String::new();
    let mut f=open(path)?;
    f.read_to_string(&mut csv_data)?;
    if csv_data.is_empty() {
        return Err("input file missing")?
    }
    Ok(csv_data)

}

fn write(data:&str,filename:&str) -> Result<(),Error> {
    let mut buffer=File::create(filename)?;
    buffer.write_all(data.as_bytes())?;
    Ok(())
}

fn open(path:PathBuf) -> Result<File,Error>{
    let f=File::open(path)?;
    Ok(f)
}

#[cfg(test)]
mod test {
    use super::PathBuf;
    use super::{
        load_csv,
        write_csv,
    };
    #[test]
    // #[ignore]
    fn test_valid_load_csv() {
        let filename=PathBuf::from(r"F:\Rust_Practise\csv_challenge\src\input\challenge.csv");
        let csv_data=load_csv(filename);
        assert!(csv_data.is_ok());
    }
    #[test]
    fn test_invalid_load_csv(){
        let filename = PathBuf::from("./input/other.csv");
        let csv_data = load_csv(filename);
        assert!(csv_data.is_err());
    }

    #[test]
    fn test_valid_write_csv(){
        
        let modified_data = r"a,b,c,d,e\nf,g,h,i,j";
        let output_file=write_csv(modified_data,r"F:\Rust_Practise\csv_challenge\src\output\test.csv");
        assert!(output_file.is_ok())
    }
}