use crate::*;

use std::time::SystemTime;


#[must_use]
pub fn copy(source_path: impl AsRef<Path>, destination_path: impl AsRef<Path>) -> WriteResult<()> {
    let source = get_entry(&source_path)?;
    let destination = get_optional_entry(&destination_path)?;
    let destination_type = destination.and_then(|e| Some(e.entry_type));

    match (source.entry_type, destination_type) {
        (EntryType::File, Some(EntryType::File)) => {
            copy_file(source_path, destination_path)?;
        }
        (EntryType::File, Some(EntryType::Directory)) => {
            let destination_path = destination_path.as_ref().join(source.name);
            copy_file(source_path, destination_path)?;
        }
        (EntryType::File, None) => {
            make_parent_directory(&destination_path)?;
            copy_file(&source_path, &destination_path)?;
        }
        (EntryType::Directory, Some(EntryType::File)) => {
            // The file is replaced by a copy of the source directory
            remove_file(&destination_path)?;
            copy_directory(&source_path, &destination_path)?;
        }
        (EntryType::Directory, Some(EntryType::Directory)) => {
            // The destination is filled with the contents of the source directory
            for entry in list_directory(source_path)? {
                let destination_path = destination_path.as_ref().join(&entry.name);
                copy(entry.path, destination_path)?;
            }
        }
        (EntryType::Directory, None) => {
            // The destination is created as a copy of the source directory
            copy_directory(&source_path, &destination_path)?;
        }
    }
    Ok(())
}

#[must_use]
fn copy_file(source_path: impl AsRef<Path>, destination_path: impl AsRef<Path>) -> WriteResult<()> {
    // Only copy file if size or last modified time is different to file at destination.
    if let Comparison::Different(last_modified) = compare_files(&source_path, &destination_path) {
        let copy_result = std::fs::copy(&source_path, &destination_path);
        io_result_to_write_result(copy_result, &destination_path.as_ref())?;
        if let Some(time) = last_modified {
            if let Ok(dest) = std::fs::File::open(&destination_path) {
                let _ = dest.set_modified(time);
            }
        }
    }
    Ok(())
}

#[must_use]
fn copy_directory(source_path: impl AsRef<Path>, destination_path: impl AsRef<Path>) -> WriteResult<()> {
    for entry in list_directory(&source_path)? {
        let destination_path = destination_path.as_ref().join(entry.name);
        copy(entry.path, &destination_path)?;
    }
    Ok(())
}

enum Comparison {
    Same,
    Different(Option<SystemTime>),
}

fn compare_files(source_path: impl AsRef<Path>, destination_path: impl AsRef<Path>) -> Comparison {
    let Ok(source) = std::fs::File::open(&source_path)    else { return Comparison::Different(None) };
    let Ok(source_metadata) = source.metadata()           else { return Comparison::Different(None) };
    let Ok(source_modified) = source_metadata.modified()  else { return Comparison::Different(None) };
    let Ok(dest) = std::fs::File::open(&destination_path) else { return Comparison::Different(Some(source_modified)) };
    let Ok(dest_metadata) = dest.metadata()               else { return Comparison::Different(Some(source_modified)) };
    let Ok(dest_modified) = dest_metadata.modified()      else { return Comparison::Different(Some(source_modified)) };
    match source_modified == dest_modified && source_metadata.len() == dest_metadata.len() {
        true => Comparison::Same,
        false => Comparison::Different(Some(source_modified)),
    }
}