use std::{
    collections::BTreeMap,
    fs::Metadata,
    path::{Path, PathBuf},
};

use eyre::WrapErr;
use lanspread_db::db::{GameCatalog, GameFileDescription};

use crate::game_paths::{VERSION_INI, is_download_protected_root_name, portable_name_key};

/// A remote manifest may describe at most this many filesystem entries.
pub(crate) const MAX_DOWNLOAD_MANIFEST_ENTRIES: usize = 100_000;
/// A single remotely described file may be at most one tebibyte.
pub(crate) const MAX_DOWNLOAD_FILE_BYTES: u64 = 1024 * 1024 * 1024 * 1024;
/// A complete remotely described game may be at most sixteen tebibytes.
pub(crate) const MAX_DOWNLOAD_MANIFEST_BYTES: u64 = 16 * MAX_DOWNLOAD_FILE_BYTES;
/// The root sentinel is parsed in memory and should contain only a version value.
pub(crate) const MAX_VERSION_INI_BYTES: u64 = 64 * 1024;
/// Portable filesystems support at least 255 bytes per ordinary component.
pub(crate) const MAX_DOWNLOAD_COMPONENT_BYTES: usize = 255;
/// Leave room for the configured game root under conservative 1,024-unit paths.
pub(crate) const MAX_DOWNLOAD_RELATIVE_PATH_BYTES: usize = 900;
const MAX_DOWNLOAD_DESTINATION_UNITS: usize = 1_000;

/// One entry whose path and shape were validated as part of a complete manifest.
#[derive(Clone, Debug)]
pub(crate) struct ValidatedDownloadEntry {
    canonical_path: String,
    protocol_path: String,
    is_dir: bool,
    size: u64,
}

impl ValidatedDownloadEntry {
    pub(crate) fn canonical_path(&self) -> &str {
        &self.canonical_path
    }

    #[cfg(test)]
    fn protocol_path(&self) -> &str {
        &self.protocol_path
    }

    pub(crate) const fn is_dir(&self) -> bool {
        self.is_dir
    }

    pub(crate) const fn size(&self) -> u64 {
        self.size
    }

    pub(crate) fn is_version_ini(&self) -> bool {
        self.canonical_path == VERSION_INI
    }

    pub(crate) fn protocol_description(&self, game_id: &str) -> GameFileDescription {
        GameFileDescription {
            game_id: game_id.to_owned(),
            relative_path: self.protocol_path.clone(),
            is_dir: self.is_dir,
            size: self.size,
        }
    }
}

/// A complete download description validated before any filesystem mutation.
#[derive(Clone, Debug)]
pub(crate) struct ValidatedDownloadManifest {
    game_id: String,
    games_folder: PathBuf,
    game_root: PathBuf,
    entries: Vec<ValidatedDownloadEntry>,
}

impl ValidatedDownloadManifest {
    /// Contains current protocol-7 descriptions within one known catalog game root.
    pub(crate) fn from_protocol_v7(
        games_folder: &Path,
        game_id: &str,
        descriptions: Vec<GameFileDescription>,
        catalog: &GameCatalog,
    ) -> eyre::Result<Self> {
        if !catalog.contains(game_id) {
            eyre::bail!("cannot download unknown catalog game {game_id}");
        }
        if descriptions.len() > MAX_DOWNLOAD_MANIFEST_ENTRIES {
            eyre::bail!(
                "download manifest for {game_id} has {} entries; limit is {MAX_DOWNLOAD_MANIFEST_ENTRIES}",
                descriptions.len()
            );
        }

        validate_game_id(game_id)?;
        let games_folder = canonical_games_folder(games_folder)?;
        let game_root = games_folder.join(game_id);
        validate_game_root(&game_root)?;
        let mut builder =
            ProtocolV7ManifestBuilder::new(game_id, Some(&game_root), descriptions.len())?;
        for description in descriptions {
            builder.push(description)?;
        }
        let entries = builder.finish()?;

        Ok(Self {
            game_id: game_id.to_owned(),
            games_folder,
            game_root,
            entries,
        })
    }

    pub(crate) fn game_id(&self) -> &str {
        &self.game_id
    }

    pub(crate) fn games_folder(&self) -> &Path {
        &self.games_folder
    }

    pub(crate) fn game_root(&self) -> &Path {
        &self.game_root
    }

    #[cfg(test)]
    fn entries(&self) -> &[ValidatedDownloadEntry] {
        &self.entries
    }

    pub(crate) fn transfer_entries(&self) -> impl Iterator<Item = &ValidatedDownloadEntry> {
        self.entries.iter().filter(|entry| !entry.is_version_ini())
    }

    pub(crate) fn protocol_descriptions(&self) -> Vec<GameFileDescription> {
        self.entries
            .iter()
            .map(|entry| entry.protocol_description(&self.game_id))
            .collect()
    }
}

/// Validates one peer's complete current-wire description before aggregation.
pub(crate) fn validate_protocol_v7_descriptions(
    game_id: &str,
    descriptions: Vec<GameFileDescription>,
) -> eyre::Result<Vec<GameFileDescription>> {
    if descriptions.len() > MAX_DOWNLOAD_MANIFEST_ENTRIES {
        eyre::bail!(
            "download manifest for {game_id} has {} entries; limit is {MAX_DOWNLOAD_MANIFEST_ENTRIES}",
            descriptions.len()
        );
    }
    validate_game_id(game_id)?;
    let mut builder = ProtocolV7ManifestBuilder::new(game_id, None, descriptions.len())?;
    for description in descriptions {
        builder.push(description)?;
    }
    Ok(builder
        .finish()?
        .into_iter()
        .map(|entry| entry.protocol_description(game_id))
        .collect())
}

struct ProtocolV7ManifestBuilder<'a> {
    game_id: &'a str,
    game_root: Option<&'a Path>,
    prefix: String,
    game_alias: String,
    entries: Vec<ValidatedDownloadEntry>,
    shapes: BTreeMap<String, EntryShape>,
    total_bytes: u64,
    saw_protocol_root: bool,
}

impl<'a> ProtocolV7ManifestBuilder<'a> {
    fn new(game_id: &'a str, game_root: Option<&'a Path>, capacity: usize) -> eyre::Result<Self> {
        Ok(Self {
            game_id,
            game_root,
            prefix: format!("{game_id}/"),
            game_alias: windows_alias_component(game_id)?,
            entries: Vec::with_capacity(capacity),
            shapes: BTreeMap::new(),
            total_bytes: 0,
            saw_protocol_root: false,
        })
    }

    fn push(&mut self, description: GameFileDescription) -> eyre::Result<()> {
        validate_protocol_game_id(self.game_id, &description)?;
        if self.take_redundant_root(&description)? {
            return Ok(());
        }
        if description.relative_path.contains('\\') {
            eyre::bail!(
                "download path must use forward slashes: {}",
                description.relative_path
            );
        }

        let canonical_path = description
            .relative_path
            .strip_prefix(&self.prefix)
            .ok_or_else(|| {
                eyre::eyre!(
                    "download path must start with exactly {}: {}",
                    self.prefix,
                    description.relative_path
                )
            })?;
        let (alias_path, components) = validate_canonical_path(canonical_path)?;
        self.validate_root_component(&components, &description.relative_path)?;
        validate_entry_shape(
            &mut self.shapes,
            &alias_path,
            description.is_dir,
            &description.relative_path,
        )?;
        self.account_size(canonical_path, &description)?;
        if let Some(game_root) = self.game_root {
            validate_existing_destination(
                game_root,
                &components,
                description.is_dir,
                &description.relative_path,
            )?;
        }
        self.entries.push(ValidatedDownloadEntry {
            canonical_path: canonical_path.to_owned(),
            protocol_path: description.relative_path,
            is_dir: description.is_dir,
            size: description.size,
        });
        Ok(())
    }

    fn take_redundant_root(&mut self, description: &GameFileDescription) -> eyre::Result<bool> {
        if description.relative_path != self.game_id {
            return Ok(false);
        }
        if description.is_dir && description.size == 0 {
            if self.saw_protocol_root {
                eyre::bail!("duplicate protocol game-root entry for {}", self.game_id);
            }
            self.saw_protocol_root = true;
            return Ok(true);
        }
        eyre::bail!(
            "the protocol game-root entry for {} must be a zero-sized directory",
            self.game_id
        )
    }

    fn validate_root_component(&self, components: &[&str], display_path: &str) -> eyre::Result<()> {
        let root_component = components
            .first()
            .expect("validated canonical paths have one component");
        if windows_alias_component(root_component)? == self.game_alias {
            eyre::bail!("download path contains a doubled game prefix: {display_path}");
        }
        if is_download_protected_root_name(root_component) {
            eyre::bail!("download path targets install or recovery state: {display_path}");
        }
        Ok(())
    }

    fn account_size(
        &mut self,
        canonical_path: &str,
        description: &GameFileDescription,
    ) -> eyre::Result<()> {
        if description.is_dir {
            if description.size != 0 {
                eyre::bail!(
                    "directory entry has a non-zero size: {}",
                    description.relative_path
                );
            }
            return Ok(());
        }
        if description.size > MAX_DOWNLOAD_FILE_BYTES {
            eyre::bail!(
                "download file exceeds the {MAX_DOWNLOAD_FILE_BYTES}-byte limit: {}",
                description.relative_path
            );
        }
        if canonical_path == VERSION_INI && description.size > MAX_VERSION_INI_BYTES {
            eyre::bail!(
                "root version.ini exceeds the {MAX_VERSION_INI_BYTES}-byte limit: {}",
                description.relative_path
            );
        }
        self.total_bytes = self
            .total_bytes
            .checked_add(description.size)
            .ok_or_else(|| eyre::eyre!("download manifest byte count overflow"))?;
        if self.total_bytes > MAX_DOWNLOAD_MANIFEST_BYTES {
            eyre::bail!("download manifest exceeds the {MAX_DOWNLOAD_MANIFEST_BYTES}-byte limit");
        }
        Ok(())
    }

    fn finish(mut self) -> eyre::Result<Vec<ValidatedDownloadEntry>> {
        self.entries
            .sort_by(|left, right| left.canonical_path.cmp(&right.canonical_path));
        let versions = self
            .entries
            .iter()
            .filter(|entry| entry.is_version_ini())
            .collect::<Vec<_>>();
        let [version_ini] = versions.as_slice() else {
            eyre::bail!(
                "expected exactly one regular root version.ini for {}, found {}",
                self.game_id,
                versions.len()
            );
        };
        if version_ini.is_dir {
            eyre::bail!(
                "root version.ini for {} must be a regular file",
                self.game_id
            );
        }
        Ok(self.entries)
    }
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum EntryShape {
    File,
    Directory,
}

fn validate_game_id(game_id: &str) -> eyre::Result<()> {
    if game_id.contains('/') || game_id.contains('\\') {
        eyre::bail!("catalog game ID must be one path component: {game_id}");
    }
    validate_component(game_id)?;
    if is_download_protected_root_name(game_id) {
        eyre::bail!("catalog game ID is reserved for application state: {game_id}");
    }
    Ok(())
}

fn validate_protocol_game_id(
    requested_game_id: &str,
    description: &GameFileDescription,
) -> eyre::Result<()> {
    if description.game_id != requested_game_id {
        eyre::bail!(
            "description for {} cannot be used to download {requested_game_id}",
            description.game_id
        );
    }
    Ok(())
}

fn canonical_games_folder(games_folder: &Path) -> eyre::Result<PathBuf> {
    if !games_folder.is_absolute() {
        eyre::bail!(
            "configured games directory must be absolute: {}",
            games_folder.display()
        );
    }
    let canonical = std::fs::canonicalize(games_folder).wrap_err_with(|| {
        format!(
            "failed to resolve configured games directory {}",
            games_folder.display()
        )
    })?;
    let metadata = std::fs::metadata(&canonical)?;
    if !metadata.is_dir() {
        eyre::bail!(
            "configured games directory is not a directory: {}",
            canonical.display()
        );
    }
    Ok(canonical)
}

fn validate_game_root(game_root: &Path) -> eyre::Result<()> {
    let Some(metadata) = symlink_metadata_if_exists(game_root)? else {
        return Ok(());
    };
    if is_link_or_reparse(&metadata) {
        eyre::bail!(
            "game root must not be a symlink or reparse point: {}",
            game_root.display()
        );
    }
    if !metadata.is_dir() {
        eyre::bail!("game root is not a directory: {}", game_root.display());
    }
    Ok(())
}

fn validate_canonical_path(path: &str) -> eyre::Result<(String, Vec<&str>)> {
    if path.is_empty() {
        eyre::bail!("download path cannot be empty");
    }
    if path.starts_with('/') || path.ends_with('/') {
        eyre::bail!("download path is not canonical: {path}");
    }
    if path.contains('\0') {
        eyre::bail!("download path contains a NUL byte");
    }
    if path.len() > MAX_DOWNLOAD_RELATIVE_PATH_BYTES {
        eyre::bail!("download path exceeds the {MAX_DOWNLOAD_RELATIVE_PATH_BYTES}-byte limit");
    }

    let components = path.split('/').collect::<Vec<_>>();
    let mut aliases = Vec::with_capacity(components.len());
    for component in &components {
        validate_component(component)?;
        aliases.push(windows_alias_component(component)?);
    }
    Ok((aliases.join("/"), components))
}

fn validate_component(component: &str) -> eyre::Result<()> {
    if component.is_empty() || matches!(component, "." | "..") {
        eyre::bail!("download path contains a non-canonical component: {component:?}");
    }
    if component.ends_with([' ', '.']) {
        eyre::bail!("download path component has a trailing dot or space: {component}");
    }
    if component.len() > MAX_DOWNLOAD_COMPONENT_BYTES {
        eyre::bail!(
            "download path component exceeds the {MAX_DOWNLOAD_COMPONENT_BYTES}-byte limit"
        );
    }
    if component.chars().any(|character| {
        character <= '\u{1f}' || matches!(character, '<' | '>' | ':' | '"' | '|' | '?' | '*')
    }) {
        eyre::bail!("download path component is not portable: {component}");
    }
    let device_stem = component.split('.').next().unwrap_or_default();
    if is_windows_device_name(device_stem) {
        eyre::bail!("download path uses a Windows device name: {component}");
    }
    if looks_like_dos_short_name(component) {
        eyre::bail!("download path resembles a Windows short-name alias: {component}");
    }
    Ok(())
}

fn windows_alias_component(component: &str) -> eyre::Result<String> {
    validate_component(component)?;
    Ok(portable_name_key(component))
}

fn is_windows_device_name(stem: &str) -> bool {
    let upper = stem.to_ascii_uppercase();
    matches!(upper.as_str(), "CON" | "PRN" | "AUX" | "NUL")
        || upper
            .strip_prefix("COM")
            .or_else(|| upper.strip_prefix("LPT"))
            .is_some_and(|number| {
                (number.len() == 1 && matches!(number.as_bytes()[0], b'1'..=b'9'))
                    || matches!(number, "¹" | "²" | "³")
            })
}

fn looks_like_dos_short_name(component: &str) -> bool {
    let stem = component.split('.').next().unwrap_or_default();
    stem.rsplit_once('~').is_some_and(|(prefix, suffix)| {
        !prefix.is_empty()
            && !suffix.is_empty()
            && suffix.len() <= 6
            && suffix.bytes().all(|byte| byte.is_ascii_digit())
    })
}

fn validate_entry_shape(
    shapes: &mut BTreeMap<String, EntryShape>,
    alias_path: &str,
    is_dir: bool,
    display_path: &str,
) -> eyre::Result<()> {
    let shape = if is_dir {
        EntryShape::Directory
    } else {
        EntryShape::File
    };
    if shapes.insert(alias_path.to_owned(), shape).is_some() {
        eyre::bail!("duplicate or platform-alias download path: {display_path}");
    }

    let mut parent = alias_path;
    while let Some((prefix, _)) = parent.rsplit_once('/') {
        if shapes.get(prefix) == Some(&EntryShape::File) {
            eyre::bail!("download path descends through a file: {display_path}");
        }
        parent = prefix;
    }

    if shape == EntryShape::File {
        let descendant_prefix = format!("{alias_path}/");
        if shapes
            .range(descendant_prefix.clone()..)
            .next()
            .is_some_and(|(candidate, _)| candidate.starts_with(&descendant_prefix))
        {
            eyre::bail!("download file conflicts with a described child: {display_path}");
        }
    }
    Ok(())
}

fn validate_existing_destination(
    game_root: &Path,
    components: &[&str],
    is_dir: bool,
    display_path: &str,
) -> eyre::Result<()> {
    let mut destination = game_root.to_path_buf();
    for component in components {
        destination.push(component);
    }
    if platform_path_units(&destination) > MAX_DOWNLOAD_DESTINATION_UNITS {
        eyre::bail!(
            "download destination exceeds the {MAX_DOWNLOAD_DESTINATION_UNITS}-unit limit: {display_path}"
        );
    }

    destination = game_root.to_path_buf();
    for (index, component) in components.iter().enumerate() {
        destination.push(component);
        let Some(metadata) = symlink_metadata_if_exists(&destination)? else {
            continue;
        };
        if is_link_or_reparse(&metadata) {
            eyre::bail!("download destination contains a symlink or reparse point: {display_path}");
        }
        let is_final = index + 1 == components.len();
        if !is_final && !metadata.is_dir() {
            eyre::bail!("download destination descends through a file: {display_path}");
        }
        if is_final && ((is_dir && !metadata.is_dir()) || (!is_dir && !metadata.is_file())) {
            eyre::bail!("download destination has the wrong filesystem type: {display_path}");
        }
    }
    Ok(())
}

#[cfg(unix)]
fn platform_path_units(path: &Path) -> usize {
    use std::os::unix::ffi::OsStrExt;

    path.as_os_str().as_bytes().len()
}

#[cfg(windows)]
fn platform_path_units(path: &Path) -> usize {
    use std::os::windows::ffi::OsStrExt;

    path.as_os_str().encode_wide().count()
}

#[cfg(not(any(unix, windows)))]
fn platform_path_units(path: &Path) -> usize {
    path.as_os_str().to_string_lossy().len()
}

fn symlink_metadata_if_exists(path: &Path) -> eyre::Result<Option<Metadata>> {
    match std::fs::symlink_metadata(path) {
        Ok(metadata) => Ok(Some(metadata)),
        Err(error) if error.kind() == std::io::ErrorKind::NotFound => Ok(None),
        Err(error) => Err(error.into()),
    }
}

fn is_link_or_reparse(metadata: &Metadata) -> bool {
    metadata.file_type().is_symlink() || is_windows_reparse_point(metadata)
}

#[cfg(windows)]
fn is_windows_reparse_point(metadata: &Metadata) -> bool {
    use std::os::windows::fs::MetadataExt;

    const FILE_ATTRIBUTE_REPARSE_POINT: u32 = 0x400;
    metadata.file_attributes() & FILE_ATTRIBUTE_REPARSE_POINT != 0
}

#[cfg(not(windows))]
const fn is_windows_reparse_point(_metadata: &Metadata) -> bool {
    false
}

#[cfg(test)]
mod tests {
    use std::collections::BTreeMap;

    use super::*;
    use crate::test_support::TempDir;

    #[derive(Debug, PartialEq, Eq)]
    enum TreeEntry {
        Directory,
        File(Vec<u8>),
        Symlink(PathBuf),
        Other,
    }

    fn catalog() -> GameCatalog {
        GameCatalog::from_ids(["game".to_owned()])
    }

    fn file(path: &str, size: u64) -> GameFileDescription {
        GameFileDescription {
            game_id: "game".to_owned(),
            relative_path: path.to_owned(),
            is_dir: false,
            size,
        }
    }

    fn directory(path: &str) -> GameFileDescription {
        GameFileDescription {
            game_id: "game".to_owned(),
            relative_path: path.to_owned(),
            is_dir: true,
            size: 0,
        }
    }

    fn valid_descriptions() -> Vec<GameFileDescription> {
        vec![
            directory("game"),
            file("game/archive.eti", 10),
            file("game/version.ini", 8),
        ]
    }

    fn validate(
        temp: &TempDir,
        descriptions: Vec<GameFileDescription>,
    ) -> eyre::Result<ValidatedDownloadManifest> {
        ValidatedDownloadManifest::from_protocol_v7(temp.path(), "game", descriptions, &catalog())
    }

    fn snapshot_tree(root: &Path) -> BTreeMap<PathBuf, TreeEntry> {
        walkdir::WalkDir::new(root)
            .follow_links(false)
            .into_iter()
            .map(|entry| entry.expect("test tree should be readable"))
            .filter(|entry| entry.path() != root)
            .map(|entry| {
                let relative = entry
                    .path()
                    .strip_prefix(root)
                    .expect("entry should be below root")
                    .to_path_buf();
                let file_type = entry.file_type();
                let value = if file_type.is_dir() {
                    TreeEntry::Directory
                } else if file_type.is_file() {
                    TreeEntry::File(
                        std::fs::read(entry.path()).expect("test file should be readable"),
                    )
                } else if file_type.is_symlink() {
                    TreeEntry::Symlink(
                        std::fs::read_link(entry.path()).expect("test link should be readable"),
                    )
                } else {
                    TreeEntry::Other
                };
                (relative, value)
            })
            .collect()
    }

    fn write_file(path: &Path, bytes: &[u8]) {
        if let Some(parent) = path.parent() {
            std::fs::create_dir_all(parent).expect("parent should be created");
        }
        std::fs::write(path, bytes).expect("test file should be written");
    }

    fn assert_rejected_without_mutation(descriptions: Vec<GameFileDescription>) {
        let temp = TempDir::new("lanspread-manifest-unchanged");
        write_file(&temp.game_root().join("archive.eti"), b"original");
        write_file(&temp.game_root().join("version.ini"), b"20250101");
        write_file(&temp.game_root().join("local/save.dat"), b"save");
        write_file(&temp.path().join("sibling/local/save.dat"), b"sibling");
        let before = snapshot_tree(temp.path());

        assert!(validate(&temp, descriptions).is_err());
        assert_eq!(snapshot_tree(temp.path()), before);
    }

    #[test]
    fn protocol_v7_adapter_strips_exact_game_prefix() {
        let temp = TempDir::new("lanspread-manifest-valid");
        let manifest = validate(&temp, valid_descriptions()).expect("manifest should validate");

        let paths = manifest
            .entries()
            .iter()
            .map(ValidatedDownloadEntry::canonical_path)
            .collect::<Vec<_>>();
        assert_eq!(paths, ["archive.eti", "version.ini"]);
        let version_ini = manifest
            .entries()
            .iter()
            .find(|entry| entry.is_version_ini())
            .expect("version.ini should exist");
        assert_eq!(version_ini.protocol_path(), "game/version.ini");
    }

    #[test]
    fn rejects_unknown_catalog_game() {
        let temp = TempDir::new("lanspread-manifest-unknown");
        let error = ValidatedDownloadManifest::from_protocol_v7(
            temp.path(),
            "unknown",
            Vec::new(),
            &catalog(),
        )
        .expect_err("unknown game should fail");
        assert!(error.to_string().contains("unknown catalog game"));
    }

    #[test]
    fn rejects_missing_different_and_doubled_game_prefixes() {
        let temp = TempDir::new("lanspread-manifest-prefix");
        for path in ["version.ini", "other/version.ini", "game/game/version.ini"] {
            let descriptions = vec![file("game/archive.eti", 10), file(path, 8)];
            assert!(validate(&temp, descriptions).is_err(), "accepted {path}");
        }
    }

    #[test]
    fn rejects_cross_game_description_identity() {
        let temp = TempDir::new("lanspread-manifest-cross-game");
        let mut descriptions = valid_descriptions();
        descriptions[1].game_id = "other".to_owned();
        assert!(validate(&temp, descriptions).is_err());
    }

    #[test]
    fn rejects_noncanonical_and_nonportable_paths() {
        let temp = TempDir::new("lanspread-manifest-noncanonical");
        for path in [
            "game/a\\b.eti",
            "game//archive.eti",
            "game/./archive.eti",
            "game/../archive.eti",
            "game/archive.eti/",
            "game/C:/archive.eti",
            "game/archive?.eti",
            "game/archive.eti\0suffix",
        ] {
            let descriptions = vec![file(path, 10), file("game/version.ini", 8)];
            assert!(validate(&temp, descriptions).is_err(), "accepted {path:?}");
        }
    }

    #[test]
    fn rejects_portability_aliases_and_path_length_overflows() {
        let temp = TempDir::new("lanspread-manifest-portability");
        for path in [
            "game/.ſync/state",
            "game/COM¹.txt",
            "game/LPT³.log",
            "game/LOCAL~1/save.dat",
        ] {
            let descriptions = vec![file(path, 1), file("game/version.ini", 8)];
            assert!(validate(&temp, descriptions).is_err(), "accepted {path}");
        }

        let long_component = format!("game/{}", "a".repeat(MAX_DOWNLOAD_COMPONENT_BYTES + 1));
        assert!(
            validate(
                &temp,
                vec![file(&long_component, 1), file("game/version.ini", 8)]
            )
            .is_err()
        );

        let long_relative = std::iter::repeat_n("a".repeat(200), 5)
            .collect::<Vec<_>>()
            .join("/");
        let long_path = format!("game/{long_relative}");
        assert!(
            validate(
                &temp,
                vec![file(&long_path, 1), file("game/version.ini", 8)]
            )
            .is_err()
        );
    }

    #[test]
    fn rejects_install_and_recovery_owned_roots() {
        let temp = TempDir::new("lanspread-manifest-reserved");
        for component in [
            "local",
            "LOCAL",
            ".local.installing",
            ".local.backup",
            ".sync",
            ".lanspread",
            ".lanspread.json",
            ".lanspread.json.tmp",
            ".lanspread_owned",
            ".softlan_first_start_done",
            ".softlan_game_installed",
            ".version.ini.tmp",
            ".version.ini.discarded",
            "install_intent.json",
            "install_intent.json.tmp",
        ] {
            let path = format!("game/{component}/payload.bin");
            let descriptions = vec![file(&path, 10), file("game/version.ini", 8)];
            assert!(
                validate(&temp, descriptions).is_err(),
                "accepted protected path {path}"
            );
        }
    }

    #[test]
    fn rejects_duplicates_platform_aliases_and_shape_conflicts() {
        let temp = TempDir::new("lanspread-manifest-alias");
        let cases = [
            vec![file("game/A.eti", 1), file("game/a.eti", 1)],
            vec![file("game/archive.eti", 1), file("game/archive.eti", 1)],
            vec![file("game/con.txt", 1)],
            vec![file("game/archive.eti.", 1)],
            vec![file("game/archive.eti ", 1)],
            vec![file("game/dir", 1), file("game/dir/child", 1)],
            vec![file("game/dir/child", 1), file("game/dir", 1)],
            vec![directory("game/dir"), file("game/dir", 1)],
            vec![directory("game"), directory("game")],
        ];
        for mut descriptions in cases {
            descriptions.push(file("game/version.ini", 8));
            assert!(validate(&temp, descriptions).is_err());
        }
    }

    #[test]
    fn raw_peer_validation_rejects_duplicates_before_consensus() {
        let descriptions = vec![
            file("game/version.ini", 8),
            file("game/archive.eti", 1),
            file("game/archive.eti", 1),
        ];
        assert!(validate_protocol_v7_descriptions("game", descriptions).is_err());
    }

    #[test]
    fn requires_exactly_one_regular_root_version_ini() {
        let temp = TempDir::new("lanspread-manifest-version");
        assert!(validate(&temp, vec![file("game/archive.eti", 1)]).is_err());
        assert!(
            validate(
                &temp,
                vec![file("game/version.ini", 8), file("game/version.ini", 8)]
            )
            .is_err()
        );
        assert!(validate(&temp, vec![directory("game/version.ini")]).is_err());
    }

    #[test]
    fn rejects_nonzero_directory_and_size_limits() {
        let temp = TempDir::new("lanspread-manifest-limits");
        let mut bad_dir = directory("game/data");
        bad_dir.size = 1;
        assert!(validate(&temp, vec![bad_dir, file("game/version.ini", 8)]).is_err());
        assert!(
            validate(
                &temp,
                vec![
                    file("game/archive.eti", MAX_DOWNLOAD_FILE_BYTES + 1),
                    file("game/version.ini", 8),
                ]
            )
            .is_err()
        );
        assert!(
            validate(
                &temp,
                vec![
                    file("game/version.ini", MAX_VERSION_INI_BYTES + 1),
                    file("game/archive.eti", 1),
                ]
            )
            .is_err()
        );

        let descriptions = vec![file("game/version.ini", 8); MAX_DOWNLOAD_MANIFEST_ENTRIES + 1];
        assert!(validate(&temp, descriptions).is_err());
    }

    #[test]
    fn hostile_late_descriptor_leaves_filesystem_unchanged() {
        let temp = TempDir::new("lanspread-manifest-zero-mutation");
        let game_root = temp.game_root();
        std::fs::create_dir_all(&game_root).expect("game root should be created");
        std::fs::write(game_root.join("archive.eti"), b"original")
            .expect("existing archive should be written");
        std::fs::write(game_root.join("version.ini"), b"20250101")
            .expect("existing version should be written");

        let descriptions = vec![
            file("game/archive.eti", 1),
            file("game/version.ini", 8),
            file("game/local/save.dat", 1),
        ];
        assert!(validate(&temp, descriptions).is_err());

        assert_eq!(
            std::fs::read(game_root.join("archive.eti")).expect("archive should remain"),
            b"original"
        );
        assert_eq!(
            std::fs::read(game_root.join("version.ini")).expect("version should remain"),
            b"20250101"
        );
        assert_eq!(
            std::fs::read_dir(&game_root)
                .expect("game root should remain readable")
                .count(),
            2
        );
    }

    #[test]
    fn rejection_categories_leave_the_complete_tree_unchanged() {
        let cases = [
            vec![file("game/version.ini", 8), file("other/local/save.dat", 1)],
            vec![file("game/version.ini", 8), file("game/local/save.dat", 1)],
            vec![file("game/version.ini", 8), file("game/.sync/state", 1)],
            vec![file("game/version.ini", 8), file("game/../escape", 1)],
            vec![
                file("game/version.ini", 8),
                file("game/A.eti", 1),
                file("game/a.eti", 1),
            ],
            vec![
                file("game/version.ini", 8),
                file("game/dir", 1),
                file("game/dir/child", 1),
            ],
            vec![file("game/archive.eti", 1)],
            vec![directory("game/version.ini")],
            vec![
                file("game/version.ini", 8),
                file("game/archive.eti", MAX_DOWNLOAD_FILE_BYTES + 1),
            ],
            vec![
                directory("game"),
                directory("game"),
                file("game/version.ini", 8),
            ],
        ];
        for descriptions in cases {
            assert_rejected_without_mutation(descriptions);
        }

        assert_rejected_without_mutation(vec![
            file("game/version.ini", 8);
            MAX_DOWNLOAD_MANIFEST_ENTRIES + 1
        ]);
    }

    #[cfg(unix)]
    #[test]
    fn rejects_symlink_game_roots_and_destination_components() {
        use std::os::unix::fs::symlink;

        let root_link = TempDir::new("lanspread-manifest-root-link");
        let outside = TempDir::new("lanspread-manifest-outside");
        symlink(outside.path(), root_link.path().join("game"))
            .expect("game root symlink should be created");
        assert!(validate(&root_link, valid_descriptions()).is_err());

        let child_link = TempDir::new("lanspread-manifest-child-link");
        std::fs::create_dir_all(child_link.game_root()).expect("game root should be created");
        symlink(outside.path(), child_link.game_root().join("payload"))
            .expect("child symlink should be created");
        let descriptions = vec![
            file("game/payload/file.bin", 1),
            file("game/version.ini", 8),
        ];
        assert!(validate(&child_link, descriptions).is_err());
    }
}