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

use sha2::{Digest, Sha256};

/// Immutable content-addressed object storage under {data_dir}/objects/{hash[:2]}/{hash}.{ext}.
/// Content is deduplicated: storing identical bytes twice keeps the first object.
pub struct ObjectStore {
    pub root: PathBuf,
}

/// One ingested artifact (file content hashed and copied into the object store).
#[derive(Debug, Clone)]
pub struct StoredObject {
    /// sha256 of content
    pub hash: String,
    /// path relative to the object root (immutable stored path)
    pub stored_path: String,
    /// file name as produced by the worker, safe for /data mounts
    pub mount_name: String,
    pub size: u64,
}

impl ObjectStore {
    pub fn new(data_dir: &str) -> Self {
        ObjectStore { root: Path::new(data_dir).join("objects") }
    }

    /// Store raw bytes by content hash. Returns (hash, stored relative path).
    pub fn store(&self, bytes: &[u8], filename: &str) -> std::io::Result<(String, String)> {
        let hash = format!("{:x}", Sha256::digest(bytes));
        let dir = self.root.join(&hash[..2]);
        std::fs::create_dir_all(&dir)?;
        let ext = safe_ext(filename);
        let path = dir.join(format!("{hash}.{ext}"));
        if !path.is_file() {
            // Atomic write in the final directory; suffix append (not with_extension)
            // so different source extensions cannot collide on one tmp name.
            let tmp = dir.join(format!("{hash}.{ext}.tmp"));
            std::fs::write(&tmp, bytes)?;
            std::fs::rename(&tmp, &path)?;
        }
        let rel = path
            .strip_prefix(&self.root)
            .map(|p| p.to_string_lossy().into_owned())
            .unwrap_or_else(|_| path.to_string_lossy().into_owned());
        Ok((hash, rel))
    }

    /// Map a stored relative path (server controlled) back to an absolute path.
    pub fn absolute(&self, rel: &str) -> PathBuf {
        self.root.join(rel)
    }

    /// Hash and ingest every regular file under an output directory (worker
    /// artifacts). Returns one entry per file, sorted for determinism.
    /// Rejects symlinked entries.
    pub fn ingest_directory(&self, dir: &Path) -> std::io::Result<Vec<StoredObject>> {
        let mut files: Vec<PathBuf> = Vec::new();
        collect_files(dir, dir, &mut files)?;
        files.sort();
        let mut out = Vec::with_capacity(files.len());
        for f in files {
            let is_symlink = f.symlink_metadata()?.file_type().is_symlink()
                || std::fs::symlink_metadata(&f)?.file_type().is_symlink();
            if is_symlink {
                return Err(std::io::Error::new(
                    std::io::ErrorKind::InvalidInput,
                    "symlinked artifact rejected",
                ));
            }
            let bytes = std::fs::read(&f)?;
            let mount_name = f
                .file_name()
                .and_then(|n| n.to_str())
                .unwrap_or("artifact.bin")
                .to_string();
            let rel_path = f.strip_prefix(dir).expect("strip_prefix");
            let (hash, stored_path) =
                self.store(&bytes, &mount_name)?;
            out.push(StoredObject {
                hash,
                stored_path,
                mount_name: rel_path.display().to_string(),
                size: bytes.len() as u64,
            });
        }
        Ok(out)
    }
}

fn collect_files(_root: &Path, dir: &Path, out: &mut Vec<PathBuf>) -> std::io::Result<()> {
    for entry in std::fs::read_dir(dir)? {
        let p = entry?.path();
        let ty = p.symlink_metadata()?.file_type();
        if ty.is_symlink() {
            // path traversal defense: no symlinked artifacts, ever
            return Err(std::io::Error::new(
                std::io::ErrorKind::InvalidInput,
                "symlink in artifact tree rejected",
            ));
        }
        if ty.is_dir() {
            collect_files(_root, &p, out)?;
        } else {
            out.push(p);
        }
    }
    Ok(())
}

/// Sanitize a filename for use as an object extension: only the final
/// extension survives, restricted to alphanumeric chars.
fn safe_ext(filename: &str) -> String {
    let base = filename.rsplit('/').next().unwrap_or("data");
    let e = base.rsplit('.').next().unwrap_or("bin").to_string();
    let v: String = e.chars().filter(|c| c.is_ascii_alphanumeric()).collect();
    if v.is_empty() || v.parse::<usize>().is_ok() {
        "bin".into()
    } else {
        v.to_lowercase()
    }
}

/// Public wrapper used when a filename has no usable extension.
pub fn filename_or_bin(name: &str, fallback: &str) -> String {
    let base = name.rsplit('/').next().unwrap_or(fallback);
    let v: String = base
        .chars()
        .filter(|c| c.is_ascii_alphanumeric() || matches!(c, '.' | '-' | '_'))
        .collect();
    if v.is_empty() || v == "." {
        fallback.into()
    } else {
        v
    }
}

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

    fn tmp_store(tag: &str) -> (tempfile::TempDir, ObjectStore) {
        let t = tempfile::tempdir_in("/tmp/opencode").unwrap();
        let store = ObjectStore::new(t.path().join(tag).to_str().unwrap());
        (t, store)
    }

    #[test]
    fn store_is_content_addressed_and_deduplicated() {
        let (_t, s) = tmp_store("objs1");
        let (h1, p1) = s.store(b"hello world", "a.csv").unwrap();
        let (h2, p2) = s.store(b"hello world", "b.csv").unwrap();
        assert_eq!(h1, h2);
        assert_eq!(p1, p2);
        assert!(p1.starts_with(&h1[..2]), "{p1}");
        let abs = s.absolute(&p1);
        assert_eq!(std::fs::read(&abs).unwrap(), b"hello world".to_vec());
        assert!(s.root.join(&p1) == abs, "stored path resolves under root");
    }

    #[test]
    fn same_stem_different_extension_no_collision() {
        let (_t, s) = tmp_store("objs2");
        let (_, a) = s.store(b"csv-bytes", "obj.csv").unwrap();
        let (_, b) = s.store(b"json-bytes", "obj.json").unwrap();
        assert_ne!(a, b);
        assert!(!a.ends_with(".tmp"));
        assert!(std::fs::read(s.absolute(&a)).unwrap().starts_with(b"csv"));
    }

    #[test]
    fn ingest_directory_walks_and_rejects_symlinks() {
        let td = tempfile::tempdir_in("/tmp/opencode").unwrap();
        let out = td.path().join("out");
        let objd = out.join("objects");
        std::fs::create_dir_all(&objd).unwrap();
        std::fs::write(objd.join("data.csv"), b"date,close\n2024-01-02,10\n").unwrap();
        std::fs::write(out.join("result.json"), b"{\"status\":\"ready\"}").unwrap();
        let (_t, s) = tmp_store("objs3");
        let stored = s.ingest_directory(&out).unwrap();
        assert_eq!(stored.len(), 2);
        let names: Vec<&str> = stored.iter().map(|o| o.mount_name.as_str()).collect();
        assert!(names.contains_all(&["objects/data.csv", "result.json"]), "{names:?}");
        // same content re-ingested maps to the same stored object
        let again = s.ingest_directory(&out).unwrap();
        for o in &stored {
            assert!(again.iter().any(|n| n.hash == o.hash));
        }
        // symlink rejection
        std::os::unix::fs::symlink(
            objd.join("data.csv"),
            objd.join("data_link.csv"),
        )
        .unwrap();
        assert!(s.ingest_directory(&out).is_err());
    }
}

trait ContainsAll {
    fn contains_all(&self, needles: &[&str]) -> bool;
}
impl ContainsAll for Vec<&str> {
    fn contains_all(&self, needles: &[&str]) -> bool {
        needles.iter().all(|n| self.iter().any(|m| m.contains(n)))
    }
}