use std::{
    collections::HashMap,
    fs::{self, File},
    io::Write,
    path::{Component, Path, PathBuf},
};

use crate::{
    branding, consts::ZELLIJ_PLUGIN_PERMISSIONS_CACHE, data::PermissionType,
    input::layout::RunPluginLocation, input::plugins::PluginConfig,
};

/// sl0p fork: the plugins we ship do not ask for permission.
///
/// Upstream prompts for every plugin on first load, which is right for a wasm
/// you found on the internet and wrong for the ones that come in the tarball:
/// pane-finder is on a keybinding we ship, and answering a three-item consent
/// screen the first time you press it is a nag about our own software.
///
/// "Ours" is deliberately narrow, and never a blanket grant:
///
///   - **builtin plugins** are compiled into the binary. Asked via
///     `PluginConfig::is_builtin`, the same predicate `check_command_permission`
///     already uses to exempt them from every command check, so the two cannot
///     drift into disagreeing about what "builtin" means.
///   - **files inside a plugin directory we install into** -- the config dir's
///     `plugins/`, where the installer puts `pane-finder.wasm` and
///     `zjstatus.wasm`, and the data dir's `plugins/`, where zellij extracts
///     its own assets. Anything that can write there can already edit
///     `config.kdl`, which can bind arbitrary commands to a key, so a consent
///     screen for the wasm beside it is not buying anything.
///   - **remote plugins are never trusted**, wherever they are cached.
///
/// Everything else still prompts. This is the whole rule -- if a plugin is not
/// covered here it goes through the normal request, so the failure mode of
/// getting the directories wrong is an extra prompt, never a silent grant.
pub fn plugin_is_shipped_with_sl0ppi(
    plugin: &PluginConfig,
    shipped_plugin_dirs: &[PathBuf],
) -> bool {
    if plugin.is_builtin() {
        return true;
    }
    match &plugin.location {
        RunPluginLocation::Zellij(_) => true,
        RunPluginLocation::Remote(_) => false,
        RunPluginLocation::File(path) => {
            let path = resolved(path);
            // a relative path cannot be compared against a directory without
            // knowing the cwd it was resolved in, so we decline to trust it
            if !path.is_absolute() {
                return false;
            }
            shipped_plugin_dirs
                .iter()
                .map(|dir| resolved(dir))
                .any(|dir| dir.is_absolute() && path.starts_with(&dir))
        },
    }
}

/// The directories whose plugins we ship, for `plugin_is_shipped_with_sl0ppi`.
///
/// Derived from the environment and the default locations rather than plumbed
/// from the parsed config: a `--config-dir` given only on the command line is
/// therefore not seen here, which costs a prompt for a plugin in it and can
/// never grant one anywhere else.
pub fn shipped_plugin_dirs() -> Vec<PathBuf> {
    let config_dir = branding::env_var(branding::ENV_CONFIG_DIR, branding::ENV_CONFIG_DIR_COMPAT)
        .ok()
        .map(PathBuf::from)
        .or_else(crate::home::find_default_config_dir);
    config_dir
        .into_iter()
        .chain(std::iter::once(crate::home::get_default_data_dir()))
        .map(|dir| dir.join("plugins"))
        .collect()
}

/// Normalise a path without touching the filesystem, then resolve symlinks if
/// the file happens to be there.
///
/// The lexical pass is what stops `<plugins>/../../anywhere.wasm` from reading
/// as "inside the plugin dir"; `canonicalize` is a best-effort tightening on
/// top, since it only works for paths that exist.
fn resolved(path: &Path) -> PathBuf {
    let mut normalized = PathBuf::new();
    for component in path.components() {
        match component {
            Component::CurDir => {},
            Component::ParentDir => {
                normalized.pop();
            },
            other => normalized.push(other.as_os_str()),
        }
    }
    fs::canonicalize(&normalized).unwrap_or(normalized)
}

pub type GrantedPermission = HashMap<String, Vec<PermissionType>>;

#[derive(Default, Debug)]
pub struct PermissionCache {
    path: PathBuf,
    granted: GrantedPermission,
}

impl PermissionCache {
    pub fn cache(&mut self, plugin_name: String, permissions: Vec<PermissionType>) {
        self.granted.insert(plugin_name, permissions);
    }

    pub fn get_permissions(&self, plugin_name: String) -> Option<&Vec<PermissionType>> {
        self.granted.get(&plugin_name)
    }

    pub fn check_permissions(
        &self,
        plugin_name: String,
        permissions_to_check: &Vec<PermissionType>,
    ) -> bool {
        if let Some(target) = self.granted.get(&plugin_name) {
            let mut all_granted = true;
            for permission in permissions_to_check {
                if !target.contains(permission) {
                    all_granted = false;
                }
            }
            return all_granted;
        }

        false
    }

    pub fn from_path_or_default(cache_path: Option<PathBuf>) -> Self {
        let cache_path = cache_path.unwrap_or(ZELLIJ_PLUGIN_PERMISSIONS_CACHE.to_path_buf());

        let granted = match fs::read_to_string(cache_path.clone()) {
            Ok(raw_string) => PermissionCache::from_string(raw_string).unwrap_or_default(),
            Err(e) => {
                log::error!("Failed to read permission cache file: {}", e);
                GrantedPermission::default()
            },
        };

        PermissionCache {
            path: cache_path,
            granted,
        }
    }

    pub fn write_to_file(&self) -> std::io::Result<()> {
        let mut f = File::create(&self.path)?;
        write!(f, "{}", PermissionCache::to_string(&self.granted))?;
        Ok(())
    }
}

#[cfg(test)]
mod shipped_plugin_tests {
    use super::*;
    use crate::input::plugins::PluginTag;

    fn plugin_at(location: RunPluginLocation) -> PluginConfig {
        PluginConfig {
            path: PathBuf::new(),
            _allow_exec_host_cmd: false,
            location,
            initial_userspace_configuration: Default::default(),
            initial_cwd: None,
        }
    }

    fn file(path: &str) -> PluginConfig {
        plugin_at(RunPluginLocation::File(PathBuf::from(path)))
    }

    fn dirs() -> Vec<PathBuf> {
        vec![
            PathBuf::from("/home/someone/.config/sl0ppij/plugins"),
            PathBuf::from("/home/someone/.local/share/sl0ppij/plugins"),
        ]
    }

    #[test]
    fn builtin_plugins_are_ours() {
        // compiled into the binary: a prompt protects nothing, and
        // check_command_permission already waves them through
        let builtin = plugin_at(RunPluginLocation::Zellij(PluginTag::new("session-manager")));
        assert!(builtin.is_builtin());
        assert!(plugin_is_shipped_with_sl0ppi(&builtin, &[]));
    }

    #[test]
    fn plugins_in_our_plugin_dirs_are_ours() {
        for path in [
            "/home/someone/.config/sl0ppij/plugins/pane-finder.wasm",
            "/home/someone/.config/sl0ppij/plugins/zjstatus.wasm",
            "/home/someone/.local/share/sl0ppij/plugins/tab-bar.wasm",
        ] {
            assert!(
                plugin_is_shipped_with_sl0ppi(&file(path), &dirs()),
                "{} should be trusted",
                path
            );
        }
    }

    #[test]
    fn plugins_from_anywhere_else_still_ask() {
        for path in [
            "/tmp/downloaded.wasm",
            "/home/someone/.config/sl0ppij/not-plugins/x.wasm",
            // a sibling directory that merely starts with the same string:
            // `starts_with` on a Path compares components, not bytes, so this
            // must not match
            "/home/someone/.config/sl0ppij/plugins-evil/x.wasm",
            "relative/path.wasm",
        ] {
            assert!(
                !plugin_is_shipped_with_sl0ppi(&file(path), &dirs()),
                "{} should NOT be trusted",
                path
            );
        }
    }

    #[test]
    fn a_traversal_out_of_the_plugin_dir_is_not_ours() {
        // the point of normalising lexically: this path is "inside" the plugin
        // dir only as a string
        assert!(!plugin_is_shipped_with_sl0ppi(
            &file("/home/someone/.config/sl0ppij/plugins/../../../../tmp/evil.wasm"),
            &dirs(),
        ));
    }

    #[test]
    fn remote_plugins_are_never_ours() {
        assert!(!plugin_is_shipped_with_sl0ppi(
            &plugin_at(RunPluginLocation::Remote(
                "https://example.com/plugin.wasm".to_owned()
            )),
            &dirs(),
        ));
    }

    #[test]
    fn no_known_plugin_dirs_means_no_file_is_ours() {
        // getting the directories wrong costs a prompt, never a silent grant
        assert!(!plugin_is_shipped_with_sl0ppi(
            &file("/home/someone/.config/sl0ppij/plugins/pane-finder.wasm"),
            &[],
        ));
    }

    #[test]
    fn the_plugin_dirs_we_look_in_are_named_plugins() {
        // it does not resolve to anything real under test, but it must never
        // hand back a bare config or data dir -- that would trust every file
        // the user keeps beside their config
        for dir in shipped_plugin_dirs() {
            assert_eq!(
                dir.file_name()
                    .map(|name| name.to_string_lossy().to_string()),
                Some("plugins".to_string()),
                "{:?} is not a plugin directory",
                dir
            );
        }
    }
}