// Copyright (C) 2024-2025  The Software Heritage developers
// See the AUTHORS file at the top-level directory of this distribution
// License: GNU General Public License version 3, or any later version
// See top-level LICENSE file for more information

//! Serialization and deserialization of (small) graphs using [`serde`]

use std::path::PathBuf;

use serde::de::*;
use serde::ser::*;
use serde::*;
use webgraph::graphs::vec_graph::LabeledVecGraph;

use crate::graph::*;
use crate::properties;
use crate::{SwhGraphProperties, SWHID};

#[derive(Serialize, Deserialize)]
struct SerializedGraph<Contents, LabelNames, Persons, Strings, Timestamps> {
    swhids: Vec<SWHID>,
    contents: Contents,
    label_names: LabelNames,
    persons: Persons,
    strings: Strings,
    timestamps: Timestamps,
    /// `node_id -> (node_id, vec![label])`
    arcs: Vec<Vec<(usize, Vec<u64>)>>,
}

/// Serializes a (small) graph using [`serde`] instead of the normal serialization
pub fn serialize_with_labels_and_maps<
    S: Serializer,
    G: SwhLabeledForwardGraph + SwhGraphWithProperties,
>(
    serializer: S,
    graph: &G,
) -> Result<S::Ok, S::Error>
where
    <G as SwhGraphWithProperties>::Maps: properties::Maps,
    <G as SwhGraphWithProperties>::Contents: serde::Serialize,
    <G as SwhGraphWithProperties>::LabelNames: serde::Serialize,
    <G as SwhGraphWithProperties>::Persons: serde::Serialize,
    <G as SwhGraphWithProperties>::Strings: serde::Serialize,
    <G as SwhGraphWithProperties>::Timestamps: serde::Serialize,
{
    SerializedGraph {
        swhids: (0..graph.num_nodes())
            .map(|node| graph.properties().swhid(node))
            .collect(),
        contents: &graph.properties().contents,
        label_names: &graph.properties().label_names,
        persons: &graph.properties().persons,
        strings: &graph.properties().strings,
        timestamps: &graph.properties().timestamps,
        arcs: (0..graph.num_nodes())
            .map(|node| {
                graph
                    .untyped_labeled_successors(node)
                    .into_iter()
                    .map(|(succ, labels)| (succ, labels.into_iter().map(|label| label.0).collect()))
                    .collect()
            })
            .collect(),
    }
    .serialize(serializer)
}

#[allow(clippy::type_complexity)]
/// Deserializes a (small) graph using [`serde`] instead of the normal deserialization, and
/// returns a fully in-memory graph, as if built by
/// [`GraphBuilder`](crate::graph_builder::GraphBuilder)
///
/// The `path` is not read, but is used to set the return value of [`SwhBidirectionalGraph::path`].
pub fn deserialize_with_labels_and_maps<
    'de,
    D: Deserializer<'de>,
    TIMESTAMPS: properties::MaybeTimestamps + Deserialize<'de>,
    PERSONS: properties::MaybePersons + Deserialize<'de>,
    CONTENTS: properties::MaybeContents + Deserialize<'de>,
    STRINGS: properties::MaybeStrings + Deserialize<'de>,
    LABELNAMES: properties::MaybeLabelNames + Deserialize<'de>,
>(
    deserializer: D,
    path: PathBuf,
) -> Result<
    SwhBidirectionalGraph<
        SwhGraphProperties<properties::VecMaps, TIMESTAMPS, PERSONS, CONTENTS, STRINGS, LABELNAMES>,
        LabeledVecGraph<Vec<u64>>,
        LabeledVecGraph<Vec<u64>>,
    >,
    /* XXX: I'd like to return this instead:
    SwhBidirectionalGraph<
        SwhGraphProperties<
            impl properties::Maps + Send + Sync + 'static,
            TIMESTAMPS,
            PERSONS,
            CONTENTS,
            STRINGS,
            LABELNAMES,
        >,
        impl UnderlyingGraph + Send + Sync + 'static,
        impl UnderlyingGraph + Send + Sync + 'static,
    >,
    but it makes this function pretty hard to use, as return-position impls capture D's lifetime
    despite + 'static. See https://github.com/rust-lang/rust/issues/132364
    */
    D::Error,
> {
    let graph: SerializedGraph<_, _, _, _, _> = SerializedGraph::deserialize(deserializer)?;
    let forward_arcs: Vec<((NodeId, NodeId), Vec<u64>)> = graph
        .arcs
        .iter()
        .enumerate()
        .flat_map(|(src, arcs)| {
            arcs.iter()
                .map(move |(dst, labels)| ((src, *dst), labels.clone()))
        })
        .collect();
    let backward_arcs: Vec<((NodeId, NodeId), Vec<u64>)> = graph
        .arcs
        .iter()
        .enumerate()
        .flat_map(|(src, arcs)| {
            arcs.iter()
                .map(move |(dst, labels)| ((*dst, src), labels.clone()))
        })
        .collect();
    Ok(SwhBidirectionalGraph::from_underlying_graphs(
        path,
        LabeledVecGraph::from_arcs(forward_arcs),
        LabeledVecGraph::from_arcs(backward_arcs),
    )
    .init_properties()
    .load_properties(move |properties| {
        Ok(properties
            .with_maps(properties::VecMaps::new(graph.swhids))
            .expect("Could not join maps")
            .with_contents(graph.contents)
            .expect("Could not join VecContents")
            .with_label_names(graph.label_names)
            .expect("Could not join maps")
            .with_persons(graph.persons)
            .expect("Could not join persons")
            .with_strings(graph.strings)
            .expect("Could not join strings")
            .with_timestamps(graph.timestamps)
            .expect("Could not join timestamps"))
    })
    .expect("Could not load properties"))
}
