use std::{
    fs, io,
    path::{Path, PathBuf},
};

use serde::{Deserialize, Serialize};

use crate::sharry;

use super::{FileTrait, Uploading};

/// Description of an existing, regular file
///
/// - impl `Clone` for `clap` compatibility
/// - impl `serde` for cachefile handling
/// - impl `PartialEq..Ord` to handle multiple files given
/// - impl `AsRef<[u8]>` for hashing with `blake2b_simd`
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Ord)]
pub struct Checked {
    /// canonical path to a regular file
    path: PathBuf,
    /// size of that file
    size: u64,
    /// hash of that file
    hash: Option<String>,
}

impl AsRef<[u8]> for Checked {
    fn as_ref(&self) -> &[u8] {
        self.path.as_os_str().as_encoded_bytes()
    }
}

impl Checked {
    pub(super) fn new_direct(path: PathBuf, size: u64, hash: Option<String>) -> Self {
        Self { path, size, hash }
    }

    /// create a new checked file from some path reference
    ///
    /// # Errors
    ///
    /// - from `fs::metadata(path)` or `fs::canonicalize`
    /// - given path does not correspond to a regular file
    pub fn new(value: impl AsRef<Path>) -> io::Result<Self> {
        let meta = fs::metadata(&value)?;
        if meta.is_file() {
            Ok(Self {
                path: fs::canonicalize(&value)?,
                size: meta.len(),
                hash: None,
            })
        } else {
            Err(io::Error::new(
                io::ErrorKind::InvalidInput,
                "Not a regular file",
            ))
        }
    }

    /// calculate and store hash for this file
    ///
    /// # Errors
    ///
    /// - from `file::compute_hash`
    /// - Mismatch if file already hashed
    ///
    /// TODO this could use an error variant like `IllegalInvocation`
    pub fn hash(&mut self, on_progress: impl FnMut(u64)) -> crate::Result<()> {
        if self.hash.is_some() {
            return Err(crate::Error::mismatch("unhashed file", self.path.display()));
        }

        self.hash = Some(super::compute_hash(&self.path, self.size, on_progress)?);

        Ok(())
    }

    /// start uploading this file
    ///
    /// - try to create a new file using the client
    /// - consume `self` into a `file::Uploading` struct
    ///
    /// # Errors
    ///
    /// - from `sharry::Client::file_create`
    pub fn start_upload(
        self,
        client: &impl sharry::Client,
        uri: &sharry::Uri,
        alias_id: &sharry::AliasID,
        share_id: &sharry::ShareID,
    ) -> crate::Result<Uploading> {
        let file_id = client.file_create(uri, alias_id, share_id, &self)?;

        Ok(Uploading::new_direct(
            self.path, self.size, self.hash, file_id,
        ))
    }
}

impl FileTrait for Checked {
    fn get_name(&self) -> &str {
        <Self as FileTrait>::extract_file_name(&self.path)
    }

    fn get_size(&self) -> u64 {
        self.size
    }

    fn check_hash(&self, on_progress: impl FnMut(u64)) -> crate::Result<()> {
        super::check_hash(&self.path, self.size, self.hash.as_deref(), on_progress)
    }
}

#[cfg(test)]
mod tests {
    // tests for `Checked::start_upload` omitted, as they require a `sharry::Client`

    use tempfile::TempDir;

    use crate::{
        file::tests::{CASES, HASHES},
        test_util::create_file,
    };

    use super::*;

    #[test]
    fn new_on_existing_file_works() {
        for (content, size) in CASES {
            let file = create_file(content);
            let chk = Checked::new(file.path()).expect("creating `Checked` should succeed");

            let path = file
                .path()
                .canonicalize()
                .expect("the file should have a canonical path");

            assert_eq!(chk.path, path);
            assert_eq!(chk.size, size);
            assert!(chk.hash.is_none());

            // `FileTrait`
            assert_eq!(
                chk.get_name(),
                file.path().file_name().expect("`file_name` should succeed")
            );
            assert_eq!(chk.get_size(), size);
        }
    }

    #[test]
    fn new_on_dir_errors() {
        let tempdir = TempDir::new().expect("creating temp dir");
        let fs_root = PathBuf::from("/");

        let dirs = [tempdir.path(), fs_root.as_path()];

        for p in dirs {
            let err = Checked::new(p).expect_err("creating `Checked` should fail");
            assert_eq!(err.kind(), io::ErrorKind::InvalidInput);
            #[cfg(target_os = "linux")]
            assert_eq!(err.to_string(), "Not a regular file");
        }
    }

    #[test]
    fn new_on_nex_errors() {
        let tempdir = TempDir::new().expect("creating temp dir");
        let nex_paths = [0, 1, 2, 3, 4].map(|i| tempdir.path().join(format!("nex_{i}.ext")));

        for p in nex_paths {
            let err = Checked::new(p).expect_err("creating `Checked` should fail");
            assert_eq!(err.kind(), io::ErrorKind::NotFound);
            #[cfg(target_os = "linux")]
            assert_eq!(err.to_string(), "No such file or directory (os error 2)");
        }
    }

    #[test]
    fn hashing_works() {
        for (&(content, _), hash) in CASES.iter().zip(HASHES) {
            let file = create_file(content);
            let mut chk = Checked::new(file.path()).expect("creating `Checked` should succeed");

            chk.hash(drop).expect("`hash` should succeed");
            // `FileTrait`
            chk.check_hash(drop).expect("`check_hash` should succeed");

            assert_eq!(chk.hash, Some(hash.to_string()));
        }
    }

    #[test]
    fn hashing_again_errors() {
        for (content, _) in CASES {
            let file = create_file(content);
            let mut chk = Checked::new(file.path()).expect("creating `Checked` should succeed");

            chk.hash(drop).expect("`hash` should succeed");
            let err = chk.hash(drop).expect_err("`hash` twice should fail");

            assert!(err.is_mismatch("unhashed file", chk.path.display().to_string()));
        }
    }
}