use geth_types::BlobHash;
use std::path::{Path, PathBuf};

#[derive(Debug, thiserror::Error)]
pub enum CasError {
    #[error("io error: {0}")]
    Io(#[from] std::io::Error),
    #[error("invalid blob hash: {0}")]
    InvalidHash(String),
    #[error("blob not found: {0}")]
    NotFound(String),
}

#[derive(Clone, Debug)]
pub struct LocalCas {
    root: PathBuf,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct BlobInfo {
    pub hash: BlobHash,
    pub size_bytes: u64,
    pub path: PathBuf,
}

impl LocalCas {
    #[must_use]
    pub fn new(root: impl Into<PathBuf>) -> Self {
        Self { root: root.into() }
    }

    pub fn add_path(&self, path: &Path) -> Result<BlobInfo, CasError> {
        let bytes = std::fs::read(path)?;
        self.add_bytes(&bytes)
    }

    pub fn add_bytes(&self, bytes: &[u8]) -> Result<BlobInfo, CasError> {
        let hash = hash_bytes(bytes);
        let path = self.blob_path(&hash)?;
        if let Some(parent) = path.parent() {
            std::fs::create_dir_all(parent)?;
        }
        if !path.exists() {
            let tmp = path.with_extension("tmp");
            std::fs::write(&tmp, bytes)?;
            std::fs::rename(tmp, &path)?;
        }
        Ok(BlobInfo {
            hash,
            size_bytes: bytes.len() as u64,
            path,
        })
    }

    pub fn get_to_path(&self, hash: &BlobHash, out: &Path) -> Result<u64, CasError> {
        let path = self.blob_path(hash)?;
        if !path.exists() {
            return Err(CasError::NotFound(hash.to_string()));
        }
        if let Some(parent) = out.parent() {
            std::fs::create_dir_all(parent)?;
        }
        std::fs::copy(path, out).map_err(CasError::from)
    }

    pub fn has(&self, hash: &BlobHash) -> Result<bool, CasError> {
        Ok(self.blob_path(hash)?.exists())
    }

    pub fn remove(&self, hash: &BlobHash) -> Result<bool, CasError> {
        let path = self.blob_path(hash)?;
        if !path.exists() {
            return Ok(false);
        }
        std::fs::remove_file(path)?;
        Ok(true)
    }

    pub fn list(&self) -> Result<Vec<BlobInfo>, CasError> {
        let blobs = self.root.join("blobs");
        if !blobs.exists() {
            return Ok(Vec::new());
        }
        let mut infos = Vec::new();
        for first in std::fs::read_dir(blobs)? {
            let first = first?;
            if !first.file_type()?.is_dir() {
                continue;
            }
            for second in std::fs::read_dir(first.path())? {
                let second = second?;
                if !second.file_type()?.is_dir() {
                    continue;
                }
                for entry in std::fs::read_dir(second.path())? {
                    let entry = entry?;
                    if !entry.file_type()?.is_file() {
                        continue;
                    }
                    let hash = entry.file_name().to_string_lossy().to_string();
                    if is_valid_hash(&hash) {
                        let meta = entry.metadata()?;
                        infos.push(BlobInfo {
                            hash: BlobHash::new(hash),
                            size_bytes: meta.len(),
                            path: entry.path(),
                        });
                    }
                }
            }
        }
        infos.sort_by(|a, b| a.hash.as_str().cmp(b.hash.as_str()));
        Ok(infos)
    }

    pub fn blob_path(&self, hash: &BlobHash) -> Result<PathBuf, CasError> {
        validate_hash(hash)?;
        let hash = hash.as_str();
        Ok(self
            .root
            .join("blobs")
            .join(&hash[0..2])
            .join(&hash[2..4])
            .join(hash))
    }
}

#[must_use]
pub fn hash_bytes(bytes: &[u8]) -> BlobHash {
    BlobHash::new(blake3::hash(bytes).to_hex().to_string())
}

pub fn hash_path(path: &Path) -> Result<BlobHash, CasError> {
    let bytes = std::fs::read(path)?;
    Ok(hash_bytes(&bytes))
}

pub fn validate_hash(hash: &BlobHash) -> Result<(), CasError> {
    if is_valid_hash(hash.as_str()) {
        Ok(())
    } else {
        Err(CasError::InvalidHash(hash.to_string()))
    }
}

#[must_use]
pub fn is_valid_hash(hash: &str) -> bool {
    hash.len() == 64 && hash.bytes().all(|byte| byte.is_ascii_hexdigit())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn cas_add_get_has_list() {
        let dir = tempfile::tempdir().expect("tempdir");
        let cas = LocalCas::new(dir.path());
        let info = cas.add_bytes(b"hello geth").expect("add");
        assert!(cas.has(&info.hash).expect("has"));
        assert_eq!(cas.list().expect("list").len(), 1);
        let out = dir.path().join("out.txt");
        cas.get_to_path(&info.hash, &out).expect("get");
        assert_eq!(std::fs::read(out).expect("read"), b"hello geth");
    }

    #[test]
    fn cas_remove_deletes_blob_file() {
        let dir = tempfile::tempdir().expect("tempdir");
        let cas = LocalCas::new(dir.path());
        let info = cas.add_bytes(b"remove me").expect("add");

        assert!(cas.remove(&info.hash).expect("remove"));
        assert!(!cas.has(&info.hash).expect("has after remove"));
        assert!(!cas.remove(&info.hash).expect("remove missing"));
    }
}