use std::fmt;

use rustc_data_structures::stable_hash::{StableHash, StableHashCtxt, StableHasher};
use rustc_span::LocalExpnId;

rustc_index::newtype_index! {
    /// Identifies an AST node.
    ///
    /// This identifies top-level definitions, expressions, and everything in between.
    /// This is later turned into [`DefId`] and `HirId` for the HIR.
    ///
    /// [`DefId`]: rustc_span::def_id::DefId
    #[encodable]
    #[orderable]
    #[debug_format = "NodeId({})"]
    pub struct NodeId {
        /// The [`NodeId`] used to represent the root of the crate.
        const CRATE_NODE_ID = 0;
    }
}

impl StableHash for NodeId {
    #[inline]
    fn stable_hash<Hcx: StableHashCtxt>(&self, _: &mut Hcx, _: &mut StableHasher) {
        // This impl is never called but is necessary for types implementing `StableHash` such as
        // `MainDefinition` and `DocLinkResMap` (both of which occur in `ResolverGlobalCtxt`).
        panic!("Node IDs should not appear in incremental state");
    }
}

rustc_data_structures::define_id_collections!(NodeMap, NodeSet, NodeMapEntry, NodeId);

/// When parsing and at the beginning of doing expansions, we initially give all AST nodes
/// this dummy AST [`NodeId`]. Then, during a later phase of expansion, we renumber them
/// to have small, positive IDs.
pub const DUMMY_NODE_ID: NodeId = NodeId::MAX;

impl NodeId {
    pub fn placeholder_from_expn_id(expn_id: LocalExpnId) -> Self {
        NodeId::from_u32(expn_id.as_u32())
    }

    pub fn placeholder_to_expn_id(self) -> LocalExpnId {
        LocalExpnId::from_u32(self.as_u32())
    }
}

impl fmt::Display for NodeId {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(&self.as_u32(), f)
    }
}