use crate::config::NetworkMode;
use crate::config::NetworkProxyConfig;
use crate::policy::DomainPattern;
use crate::policy::compile_globset;
use crate::runtime::ConfigReloader;
use crate::runtime::ConfigState;
use anyhow::Context;
use anyhow::Result;
use async_trait::async_trait;
use codex_app_server_protocol::ConfigLayerSource;
use codex_core::config::CONFIG_TOML_FILE;
use codex_core::config::ConstraintError;
use codex_core::config::find_codex_home;
use codex_core::config_loader::CloudRequirementsLoader;
use codex_core::config_loader::ConfigLayerStack;
use codex_core::config_loader::ConfigLayerStackOrdering;
use codex_core::config_loader::LoaderOverrides;
use codex_core::config_loader::RequirementSource;
use codex_core::config_loader::load_config_layers_state;
use serde::Deserialize;
use std::collections::HashSet;
use tokio::sync::RwLock;

pub use crate::runtime::BlockedRequest;
pub use crate::runtime::BlockedRequestArgs;
pub use crate::runtime::NetworkProxyState;
#[cfg(test)]
pub(crate) use crate::runtime::network_proxy_state_for_policy;

pub(crate) async fn build_default_config_state_and_reloader()
-> Result<(ConfigState, MtimeConfigReloader)> {
    let (state, layer_mtimes) = build_config_state_with_mtimes().await?;
    Ok((state, MtimeConfigReloader::new(layer_mtimes)))
}

async fn build_config_state_with_mtimes() -> Result<(ConfigState, Vec<LayerMtime>)> {
    // Load config through `codex-core` so we inherit the same layer ordering and semantics as the
    // rest of Codex (system/managed layers, user layers, session flags, etc.).
    let codex_home = find_codex_home().context("failed to resolve CODEX_HOME")?;
    let cli_overrides = Vec::new();
    let overrides = LoaderOverrides::default();
    let config_layer_stack = load_config_layers_state(
        &codex_home,
        None,
        &cli_overrides,
        overrides,
        CloudRequirementsLoader::default(),
    )
    .await
    .context("failed to load Codex config")?;

    let cfg_path = codex_home.join(CONFIG_TOML_FILE);

    // Deserialize from the merged effective config, rather than parsing config.toml ourselves.
    // This avoids a second parser/merger implementation (and the drift that comes with it).
    let merged_toml = config_layer_stack.effective_config();
    let config: NetworkProxyConfig = merged_toml
        .try_into()
        .context("failed to deserialize network proxy config")?;

    // Security boundary: user-controlled layers must not be able to widen restrictions set by
    // trusted/managed layers (e.g., MDM). Enforce this before building runtime state.
    let constraints = enforce_trusted_constraints(&config_layer_stack, &config)?;

    let layer_mtimes = collect_layer_mtimes(&config_layer_stack);
    let deny_set = compile_globset(&config.network.denied_domains)?;
    let allow_set = compile_globset(&config.network.allowed_domains)?;
    Ok((
        ConfigState {
            config,
            allow_set,
            deny_set,
            constraints,
            cfg_path,
            blocked: std::collections::VecDeque::new(),
        },
        layer_mtimes,
    ))
}

fn collect_layer_mtimes(stack: &ConfigLayerStack) -> Vec<LayerMtime> {
    stack
        .get_layers(ConfigLayerStackOrdering::LowestPrecedenceFirst, false)
        .iter()
        .filter_map(|layer| {
            let path = match &layer.name {
                ConfigLayerSource::System { file } => Some(file.as_path().to_path_buf()),
                ConfigLayerSource::User { file } => Some(file.as_path().to_path_buf()),
                ConfigLayerSource::Project { dot_codex_folder } => dot_codex_folder
                    .join(CONFIG_TOML_FILE)
                    .ok()
                    .map(|p| p.as_path().to_path_buf()),
                ConfigLayerSource::LegacyManagedConfigTomlFromFile { file } => {
                    Some(file.as_path().to_path_buf())
                }
                _ => None,
            };
            path.map(LayerMtime::new)
        })
        .collect()
}

#[derive(Clone)]
struct LayerMtime {
    path: std::path::PathBuf,
    mtime: Option<std::time::SystemTime>,
}

impl LayerMtime {
    fn new(path: std::path::PathBuf) -> Self {
        let mtime = path.metadata().and_then(|m| m.modified()).ok();
        Self { path, mtime }
    }
}

pub(crate) struct MtimeConfigReloader {
    layer_mtimes: RwLock<Vec<LayerMtime>>,
}

impl MtimeConfigReloader {
    fn new(layer_mtimes: Vec<LayerMtime>) -> Self {
        Self {
            layer_mtimes: RwLock::new(layer_mtimes),
        }
    }

    async fn needs_reload(&self) -> bool {
        let guard = self.layer_mtimes.read().await;
        guard.iter().any(|layer| {
            let metadata = std::fs::metadata(&layer.path).ok();
            match (metadata.and_then(|m| m.modified().ok()), layer.mtime) {
                (Some(new_mtime), Some(old_mtime)) => new_mtime > old_mtime,
                (Some(_), None) => true,
                (None, Some(_)) => true,
                (None, None) => false,
            }
        })
    }
}

#[async_trait]
impl ConfigReloader for MtimeConfigReloader {
    async fn maybe_reload(&self) -> Result<Option<ConfigState>> {
        if !self.needs_reload().await {
            return Ok(None);
        }

        let (state, layer_mtimes) = build_config_state_with_mtimes().await?;
        let mut guard = self.layer_mtimes.write().await;
        *guard = layer_mtimes;
        Ok(Some(state))
    }

    async fn reload_now(&self) -> Result<ConfigState> {
        let (state, layer_mtimes) = build_config_state_with_mtimes().await?;
        let mut guard = self.layer_mtimes.write().await;
        *guard = layer_mtimes;
        Ok(state)
    }
}

#[derive(Debug, Default, Deserialize)]
struct PartialConfig {
    #[serde(default)]
    network: PartialNetworkConfig,
}

#[derive(Debug, Default, Deserialize)]
struct PartialNetworkConfig {
    enabled: Option<bool>,
    mode: Option<NetworkMode>,
    allow_upstream_proxy: Option<bool>,
    dangerously_allow_non_loopback_proxy: Option<bool>,
    dangerously_allow_non_loopback_admin: Option<bool>,
    #[serde(default)]
    allowed_domains: Option<Vec<String>>,
    #[serde(default)]
    denied_domains: Option<Vec<String>>,
    #[serde(default)]
    allow_unix_sockets: Option<Vec<String>>,
    #[serde(default)]
    allow_local_binding: Option<bool>,
}

#[derive(Debug, Default, Clone, PartialEq, Eq)]
pub(crate) struct NetworkProxyConstraints {
    pub(crate) enabled: Option<bool>,
    pub(crate) mode: Option<NetworkMode>,
    pub(crate) allow_upstream_proxy: Option<bool>,
    pub(crate) dangerously_allow_non_loopback_proxy: Option<bool>,
    pub(crate) dangerously_allow_non_loopback_admin: Option<bool>,
    pub(crate) allowed_domains: Option<Vec<String>>,
    pub(crate) denied_domains: Option<Vec<String>>,
    pub(crate) allow_unix_sockets: Option<Vec<String>>,
    pub(crate) allow_local_binding: Option<bool>,
}

fn enforce_trusted_constraints(
    layers: &codex_core::config_loader::ConfigLayerStack,
    config: &NetworkProxyConfig,
) -> Result<NetworkProxyConstraints> {
    let constraints = network_constraints_from_trusted_layers(layers)?;
    validate_policy_against_constraints(config, &constraints)
        .context("network proxy constraints")?;
    Ok(constraints)
}

fn network_constraints_from_trusted_layers(
    layers: &codex_core::config_loader::ConfigLayerStack,
) -> Result<NetworkProxyConstraints> {
    let mut constraints = NetworkProxyConstraints::default();
    for layer in layers.get_layers(
        codex_core::config_loader::ConfigLayerStackOrdering::LowestPrecedenceFirst,
        false,
    ) {
        // Only trusted layers contribute constraints. User-controlled layers can narrow policy but
        // must never widen beyond what managed config allows.
        if is_user_controlled_layer(&layer.name) {
            continue;
        }

        let partial: PartialConfig = layer
            .config
            .clone()
            .try_into()
            .context("failed to deserialize trusted config layer")?;

        if let Some(enabled) = partial.network.enabled {
            constraints.enabled = Some(enabled);
        }
        if let Some(mode) = partial.network.mode {
            constraints.mode = Some(mode);
        }
        if let Some(allow_upstream_proxy) = partial.network.allow_upstream_proxy {
            constraints.allow_upstream_proxy = Some(allow_upstream_proxy);
        }
        if let Some(dangerously_allow_non_loopback_proxy) =
            partial.network.dangerously_allow_non_loopback_proxy
        {
            constraints.dangerously_allow_non_loopback_proxy =
                Some(dangerously_allow_non_loopback_proxy);
        }
        if let Some(dangerously_allow_non_loopback_admin) =
            partial.network.dangerously_allow_non_loopback_admin
        {
            constraints.dangerously_allow_non_loopback_admin =
                Some(dangerously_allow_non_loopback_admin);
        }

        if let Some(allowed_domains) = partial.network.allowed_domains {
            constraints.allowed_domains = Some(allowed_domains);
        }
        if let Some(denied_domains) = partial.network.denied_domains {
            constraints.denied_domains = Some(denied_domains);
        }
        if let Some(allow_unix_sockets) = partial.network.allow_unix_sockets {
            constraints.allow_unix_sockets = Some(allow_unix_sockets);
        }
        if let Some(allow_local_binding) = partial.network.allow_local_binding {
            constraints.allow_local_binding = Some(allow_local_binding);
        }
    }
    Ok(constraints)
}

fn is_user_controlled_layer(layer: &ConfigLayerSource) -> bool {
    matches!(
        layer,
        ConfigLayerSource::User { .. }
            | ConfigLayerSource::Project { .. }
            | ConfigLayerSource::SessionFlags
    )
}

pub(crate) fn validate_policy_against_constraints(
    config: &NetworkProxyConfig,
    constraints: &NetworkProxyConstraints,
) -> std::result::Result<(), ConstraintError> {
    fn invalid_value(
        field_name: &'static str,
        candidate: impl Into<String>,
        allowed: impl Into<String>,
    ) -> ConstraintError {
        ConstraintError::InvalidValue {
            field_name,
            candidate: candidate.into(),
            allowed: allowed.into(),
            requirement_source: RequirementSource::Unknown,
        }
    }

    fn validate<T>(
        candidate: T,
        validator: impl FnOnce(&T) -> std::result::Result<(), ConstraintError>,
    ) -> std::result::Result<(), ConstraintError> {
        validator(&candidate)
    }

    let enabled = config.network.enabled;
    if let Some(max_enabled) = constraints.enabled {
        validate(enabled, move |candidate| {
            if *candidate && !max_enabled {
                Err(invalid_value(
                    "network.enabled",
                    "true",
                    "false (disabled by managed config)",
                ))
            } else {
                Ok(())
            }
        })?;
    }

    if let Some(max_mode) = constraints.mode {
        validate(config.network.mode, move |candidate| {
            if network_mode_rank(*candidate) > network_mode_rank(max_mode) {
                Err(invalid_value(
                    "network.mode",
                    format!("{candidate:?}"),
                    format!("{max_mode:?} or more restrictive"),
                ))
            } else {
                Ok(())
            }
        })?;
    }

    let allow_upstream_proxy = constraints.allow_upstream_proxy;
    validate(
        config.network.allow_upstream_proxy,
        move |candidate| match allow_upstream_proxy {
            Some(true) | None => Ok(()),
            Some(false) => {
                if *candidate {
                    Err(invalid_value(
                        "network.allow_upstream_proxy",
                        "true",
                        "false (disabled by managed config)",
                    ))
                } else {
                    Ok(())
                }
            }
        },
    )?;

    let allow_non_loopback_admin = constraints.dangerously_allow_non_loopback_admin;
    validate(
        config.network.dangerously_allow_non_loopback_admin,
        move |candidate| match allow_non_loopback_admin {
            Some(true) | None => Ok(()),
            Some(false) => {
                if *candidate {
                    Err(invalid_value(
                        "network.dangerously_allow_non_loopback_admin",
                        "true",
                        "false (disabled by managed config)",
                    ))
                } else {
                    Ok(())
                }
            }
        },
    )?;

    let allow_non_loopback_proxy = constraints.dangerously_allow_non_loopback_proxy;
    validate(
        config.network.dangerously_allow_non_loopback_proxy,
        move |candidate| match allow_non_loopback_proxy {
            Some(true) | None => Ok(()),
            Some(false) => {
                if *candidate {
                    Err(invalid_value(
                        "network.dangerously_allow_non_loopback_proxy",
                        "true",
                        "false (disabled by managed config)",
                    ))
                } else {
                    Ok(())
                }
            }
        },
    )?;

    if let Some(allow_local_binding) = constraints.allow_local_binding {
        validate(config.network.allow_local_binding, move |candidate| {
            if *candidate && !allow_local_binding {
                Err(invalid_value(
                    "network.allow_local_binding",
                    "true",
                    "false (disabled by managed config)",
                ))
            } else {
                Ok(())
            }
        })?;
    }

    if let Some(allowed_domains) = &constraints.allowed_domains {
        let managed_patterns: Vec<DomainPattern> = allowed_domains
            .iter()
            .map(|entry| DomainPattern::parse_for_constraints(entry))
            .collect();
        validate(config.network.allowed_domains.clone(), move |candidate| {
            let mut invalid = Vec::new();
            for entry in candidate {
                let candidate_pattern = DomainPattern::parse_for_constraints(entry);
                if !managed_patterns
                    .iter()
                    .any(|managed| managed.allows(&candidate_pattern))
                {
                    invalid.push(entry.clone());
                }
            }
            if invalid.is_empty() {
                Ok(())
            } else {
                Err(invalid_value(
                    "network.allowed_domains",
                    format!("{invalid:?}"),
                    "subset of managed allowed_domains",
                ))
            }
        })?;
    }

    if let Some(denied_domains) = &constraints.denied_domains {
        let required_set: HashSet<String> = denied_domains
            .iter()
            .map(|s| s.to_ascii_lowercase())
            .collect();
        validate(config.network.denied_domains.clone(), move |candidate| {
            let candidate_set: HashSet<String> =
                candidate.iter().map(|s| s.to_ascii_lowercase()).collect();
            let missing: Vec<String> = required_set
                .iter()
                .filter(|entry| !candidate_set.contains(*entry))
                .cloned()
                .collect();
            if missing.is_empty() {
                Ok(())
            } else {
                Err(invalid_value(
                    "network.denied_domains",
                    "missing managed denied_domains entries",
                    format!("{missing:?}"),
                ))
            }
        })?;
    }

    if let Some(allow_unix_sockets) = &constraints.allow_unix_sockets {
        let allowed_set: HashSet<String> = allow_unix_sockets
            .iter()
            .map(|s| s.to_ascii_lowercase())
            .collect();
        validate(
            config.network.allow_unix_sockets.clone(),
            move |candidate| {
                let mut invalid = Vec::new();
                for entry in candidate {
                    if !allowed_set.contains(&entry.to_ascii_lowercase()) {
                        invalid.push(entry.clone());
                    }
                }
                if invalid.is_empty() {
                    Ok(())
                } else {
                    Err(invalid_value(
                        "network.allow_unix_sockets",
                        format!("{invalid:?}"),
                        "subset of managed allow_unix_sockets",
                    ))
                }
            },
        )?;
    }

    Ok(())
}

fn network_mode_rank(mode: NetworkMode) -> u8 {
    match mode {
        NetworkMode::Limited => 0,
        NetworkMode::Full => 1,
    }
}