use super::registry::OPTION_SPECS;
use super::reserved::{RESERVED_OPTION_NAMES, ReservedOptionName};
use super::{OptionScope, OptionSource, OptionSpec, OptionStatus};

/// Returns the canonical option specification for a known spelling.
#[must_use]
pub fn option_spec(name: &str) -> Option<&'static OptionSpec> {
    OPTION_SPECS
        .iter()
        .find(|s| s.name == name)
        .or_else(|| OPTION_SPECS.iter().find(|s| s.aliases.contains(&name)))
}
/// Returns whether an option is required by the `aria2-rust-pro` surface.
#[must_use]
pub fn is_required_pro_option(option: &str) -> bool {
    OPTION_SPECS.iter().any(|s| {
        s.name == option
            && (s.source == OptionSource::Pro || s.source == OptionSource::CompatibilityAlias)
    })
}

/// Returns whether a status should be exposed in live option listings.
#[must_use]
pub const fn is_live_option_status(status: OptionStatus) -> bool {
    matches!(
        status,
        OptionStatus::Implemented | OptionStatus::Verified | OptionStatus::Deprecated
    )
}

/// Filters the registry while preserving canonical-name uniqueness.
fn unique_option_specs(predicate: impl Fn(&OptionSpec) -> bool) -> Vec<&'static OptionSpec> {
    let mut seen = std::collections::BTreeSet::new();
    OPTION_SPECS
        .iter()
        .filter(|spec| predicate(spec) && seen.insert(spec.name))
        .collect()
}

/// Returns all live option specs without duplicate canonical names.
#[must_use]
pub fn live_option_specs() -> Vec<&'static OptionSpec> {
    unique_option_specs(|spec| is_live_option_status(spec.status))
}

/// Returns all options available in the global scope.
#[must_use]
pub fn global_option_specs() -> Vec<&'static OptionSpec> {
    unique_option_specs(|spec| {
        matches!(spec.metadata.scope, OptionScope::Global | OptionScope::Both)
    })
}
/// Returns all options available in the per-download scope.
#[must_use]
pub fn per_download_option_specs() -> Vec<&'static OptionSpec> {
    unique_option_specs(|spec| {
        matches!(
            spec.metadata.scope,
            OptionScope::PerDownload | OptionScope::Both
        )
    })
}
/// Returns the reserved option-name table.
#[must_use]
pub const fn reserved_option_names() -> &'static [ReservedOptionName] {
    RESERVED_OPTION_NAMES
}
/// Returns the canonical RPC option name for a known spelling.
#[must_use]
pub fn rpc_option_name(name: &str) -> Option<&'static str> {
    option_spec(name).and_then(|s| s.rpc_names.first().copied())
}
/// Returns the environment-variable name associated with an option.
#[must_use]
pub fn env_var_for_option(name: &str) -> Option<String> {
    option_spec(name).map(|s| format!("ARIA2_{}", s.name.replace('-', "_").to_ascii_uppercase()))
}