//! Resolves a finger username to a response: the contents of that user's
//! plan file if one exists and is readable, or the username echoed back
//! unchanged otherwise. Input is validated first so a request can never walk
//! outside the configured plan-file directory.

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

pub trait FilesystemWrapper {
    fn exists(&self, path: &Path) -> bool;
    fn read_file(&self, path: &Path) -> String;
}

pub struct RealFilesystemWrapper;

impl FilesystemWrapper for RealFilesystemWrapper {
    fn exists(&self, path: &Path) -> bool {
        path.exists()
    }

    fn read_file(&self, path: &Path) -> String {
        let raw = match std::fs::read_to_string(path) {
            Ok(c) => c,
            Err(_) => return String::new(),
        };
        if raw.is_empty() {
            return String::new();
        }
        // Plan files are returned over the finger protocol, which expects
        // CRLF line endings; normalise whatever the file used to LF-joined
        // lines terminated by a single CRLF.
        let body = raw.lines().collect::<Vec<_>>().join("\n");
        format!("{body}\r\n")
    }
}

pub const BASE_PATH: &str = "/var/finger/users/";

pub fn process(username: &str) -> String {
    let fs = RealFilesystemWrapper;
    process_with(username, &fs, Path::new(BASE_PATH))
}

pub fn process_with(username: &str, fs: &dyn FilesystemWrapper, basepath: &Path) -> String {
    const TRAVERSAL_PATTERNS: [&str; 10] = [
        "../",
        "..\\",
        "%2e%2e%2f",
        "%2e%2e%5c",
        "%2E%2E%2F",
        "%2E%2E%5C",
        "..%2f",
        "..%5c",
        "..%2F",
        "..%5C",
    ];
    if TRAVERSAL_PATTERNS.iter().any(|p| username.contains(p)) {
        return "InvalidInput: Directory traversal detected in username\r\n".to_string();
    }
    if username.contains('/') {
        return "InvalidInput: Path detected in username\r\n".to_string();
    }

    // Plan-file lookup is case-insensitive: normalise the requested name to
    // lower-case so e.g. "Pete" resolves the on-disk "pete" plan. Plan
    // filenames are always lower-case; the original spelling is still echoed
    // back below when no plan exists. Lower-casing is ASCII-only to match
    // the byte-wise ::tolower behavior of the reference implementation.
    let lookup = username.to_ascii_lowercase();
    let plan_path: PathBuf = basepath.join(lookup);

    if !fs.exists(&plan_path) {
        return username.to_string();
    }

    let content = fs.read_file(&plan_path);
    if content.is_empty() {
        return username.to_string();
    }

    content
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::collections::HashMap;
    use std::sync::atomic::{AtomicU64, Ordering};

    #[test]
    fn valid_username_simple() {
        assert_eq!(process("john"), "john");
    }

    #[test]
    fn valid_username_with_numbers() {
        assert_eq!(process("user123"), "user123");
    }

    #[test]
    fn valid_username_with_underscore() {
        assert_eq!(process("user_name"), "user_name");
    }

    #[test]
    fn valid_username_with_hyphen() {
        assert_eq!(process("user-name"), "user-name");
    }

    #[test]
    fn valid_username_empty_string() {
        assert_eq!(process(""), "");
    }

    #[test]
    fn directory_traversal_basic_dot_dot_slash() {
        let result = process("user../file");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Directory traversal detected"));
    }

    #[test]
    fn directory_traversal_basic_dot_dot_backslash() {
        let result = process("user..\\file");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Directory traversal detected"));
    }

    #[test]
    fn directory_traversal_url_encoded_lowercase_2e2e2f() {
        let result = process("user%2e%2e%2ffile");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Directory traversal detected"));
    }

    #[test]
    fn directory_traversal_url_encoded_lowercase_2e2e5c() {
        let result = process("user%2e%2e%5cfile");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Directory traversal detected"));
    }

    #[test]
    fn directory_traversal_url_encoded_uppercase_2e2e2f() {
        let result = process("user%2E%2E%2Ffile");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Directory traversal detected"));
    }

    #[test]
    fn directory_traversal_url_encoded_uppercase_2e2e5c() {
        let result = process("user%2E%2E%5Cfile");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Directory traversal detected"));
    }

    #[test]
    fn directory_traversal_mixed_dot_dot_2f() {
        let result = process("user..%2ffile");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Directory traversal detected"));
    }

    #[test]
    fn directory_traversal_mixed_dot_dot_5c() {
        let result = process("user..%5cfile");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Directory traversal detected"));
    }

    #[test]
    fn directory_traversal_mixed_dot_dot_2f_upper() {
        let result = process("user..%2Ffile");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Directory traversal detected"));
    }

    #[test]
    fn directory_traversal_mixed_dot_dot_5c_upper() {
        let result = process("user..%5Cfile");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Directory traversal detected"));
    }

    #[test]
    fn path_detection_forward_slash() {
        let result = process("user/name");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Path detected"));
    }

    #[test]
    fn path_detection_forward_slash_at_start() {
        let result = process("/username");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Path detected"));
    }

    #[test]
    fn path_detection_forward_slash_at_end() {
        let result = process("username/");
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Path detected"));
    }

    #[test]
    fn single_dot() {
        assert_eq!(process("."), ".");
    }

    #[test]
    fn double_dot_without_slash() {
        assert_eq!(process(".."), "..");
    }

    #[test]
    fn contains_dot_but_not_traversal() {
        assert_eq!(process("user.name"), "user.name");
    }

    #[test]
    fn backslash_without_dots() {
        assert_eq!(process("user\\name"), "user\\name");
    }

    // --- Fake-filesystem tests (mirrors test_handler_mock.cpp) ---

    #[derive(Default)]
    struct FakeFilesystem {
        files: HashMap<PathBuf, String>,
    }

    impl FakeFilesystem {
        fn with_file(path: impl Into<PathBuf>, content: impl Into<String>) -> Self {
            let mut files = HashMap::new();
            files.insert(path.into(), content.into());
            FakeFilesystem { files }
        }
    }

    impl FilesystemWrapper for FakeFilesystem {
        fn exists(&self, path: &Path) -> bool {
            self.files.contains_key(path)
        }

        fn read_file(&self, path: &Path) -> String {
            self.files.get(path).cloned().unwrap_or_default()
        }
    }

    #[test]
    fn process_with_file_exists() {
        let base = Path::new("/var/finger/users/");
        let fs = FakeFilesystem::with_file(base.join("testuser"), "Mock file content\r\n");
        assert_eq!(
            process_with("testuser", &fs, base),
            "Mock file content\r\n"
        );
    }

    #[test]
    fn process_with_file_not_found() {
        let base = Path::new("/var/finger/users/");
        let fs = FakeFilesystem::default();
        assert_eq!(process_with("nonexistentuser", &fs, base), "nonexistentuser");
    }

    #[test]
    fn process_with_empty_file() {
        let base = Path::new("/var/finger/users/");
        let fs = FakeFilesystem::with_file(base.join("emptyfileuser"), "");
        assert_eq!(process_with("emptyfileuser", &fs, base), "emptyfileuser");
    }

    #[test]
    fn process_lowercases_username_for_lookup() {
        let base = Path::new("/var/finger/users/");
        let fs = FakeFilesystem::with_file(base.join("pete"), "Just another hacker.\r\n");
        assert_eq!(
            process_with("Pete", &fs, base),
            "Just another hacker.\r\n"
        );
    }

    // --- Real-filesystem tests (mirrors test_handler_real_filesystem.cpp) ---

    static TEMP_COUNTER: AtomicU64 = AtomicU64::new(0);

    struct TempDir(PathBuf);

    impl TempDir {
        fn new() -> Self {
            let n = TEMP_COUNTER.fetch_add(1, Ordering::Relaxed);
            let dir = std::env::temp_dir().join(format!(
                "finger_rs_test_{}_{n}",
                std::process::id()
            ));
            std::fs::create_dir_all(&dir).unwrap();
            TempDir(dir)
        }

        fn path(&self) -> &Path {
            &self.0
        }
    }

    impl Drop for TempDir {
        fn drop(&mut self) {
            let _ = std::fs::remove_dir_all(&self.0);
        }
    }

    fn write_file(dir: &Path, name: &str, content: &str) {
        std::fs::write(dir.join(name), content).unwrap();
    }

    #[test]
    fn real_fs_exists_with_real_file() {
        let dir = TempDir::new();
        write_file(dir.path(), "testuser", "Test content");
        let fs = RealFilesystemWrapper;
        assert!(fs.exists(&dir.path().join("testuser")));
    }

    #[test]
    fn real_fs_exists_with_nonexistent_file() {
        let dir = TempDir::new();
        let fs = RealFilesystemWrapper;
        assert!(!fs.exists(&dir.path().join("nonexistent")));
    }

    #[test]
    fn real_fs_read_file_with_simple_content() {
        let dir = TempDir::new();
        write_file(dir.path(), "simple", "Hello, World!");
        let fs = RealFilesystemWrapper;
        assert_eq!(
            fs.read_file(&dir.path().join("simple")),
            "Hello, World!\r\n"
        );
    }

    #[test]
    fn real_fs_read_file_with_multiline_content() {
        let dir = TempDir::new();
        write_file(dir.path(), "multiline", "Line 1\nLine 2\nLine 3");
        let fs = RealFilesystemWrapper;
        assert_eq!(
            fs.read_file(&dir.path().join("multiline")),
            "Line 1\nLine 2\nLine 3\r\n"
        );
    }

    #[test]
    fn real_fs_read_file_with_empty_file() {
        let dir = TempDir::new();
        write_file(dir.path(), "empty", "");
        let fs = RealFilesystemWrapper;
        assert_eq!(fs.read_file(&dir.path().join("empty")), "");
    }

    #[test]
    fn real_fs_read_file_nonexistent_file() {
        let dir = TempDir::new();
        let fs = RealFilesystemWrapper;
        assert_eq!(fs.read_file(&dir.path().join("nonexistent")), "");
    }

    #[test]
    fn process_with_existing_user_file() {
        let dir = TempDir::new();
        write_file(
            dir.path(),
            "johndoe",
            "John Doe\nSoftware Engineer\nLoves Rust",
        );
        let fs = RealFilesystemWrapper;
        assert_eq!(
            process_with("johndoe", &fs, dir.path()),
            "John Doe\nSoftware Engineer\nLoves Rust\r\n"
        );
    }

    #[test]
    fn process_with_nonexistent_user_file() {
        let dir = TempDir::new();
        let fs = RealFilesystemWrapper;
        assert_eq!(process_with("nonexistentuser", &fs, dir.path()), "nonexistentuser");
    }

    #[test]
    fn process_with_empty_user_file() {
        let dir = TempDir::new();
        write_file(dir.path(), "emptyuser", "");
        let fs = RealFilesystemWrapper;
        assert_eq!(process_with("emptyuser", &fs, dir.path()), "emptyuser");
    }

    #[test]
    fn process_with_file_containing_only_newlines() {
        let dir = TempDir::new();
        write_file(dir.path(), "newlineuser", "\n\n\n");
        let fs = RealFilesystemWrapper;
        // Line-by-line reading means the trailing empty line after the final
        // \n is not read as a separate line, resulting in "\n\n\r\n".
        assert_eq!(process_with("newlineuser", &fs, dir.path()), "\n\n\r\n");
    }

    #[test]
    fn process_directory_traversal_protection_with_real_fs() {
        let dir = TempDir::new();
        let result = process_with("../secret", &RealFilesystemWrapper, dir.path());
        assert!(result.starts_with("InvalidInput:"));
        assert!(result.contains("Directory traversal detected"));
    }

    #[test]
    fn process_with_custom_base_path() {
        let dir = TempDir::new();
        let custom_base = dir.path().join("custom_users");
        std::fs::create_dir_all(&custom_base).unwrap();
        write_file(&custom_base, "customuser", "Custom base path user");
        let fs = RealFilesystemWrapper;
        assert_eq!(
            process_with("customuser", &fs, &custom_base),
            "Custom base path user\r\n"
        );
    }

    #[test]
    fn real_fs_read_file_with_special_characters() {
        let dir = TempDir::new();
        let content = "User with special chars: \u{e0}\u{e1}\u{e2}\u{e3}\u{e4}\u{e5}\u{e6}\u{e7}\u{e8}\u{e9}\u{ea}\u{eb}";
        write_file(dir.path(), "specialuser", content);
        let fs = RealFilesystemWrapper;
        assert_eq!(
            fs.read_file(&dir.path().join("specialuser")),
            format!("{content}\r\n")
        );
    }
}