"""COINs link prediction / query answering — inference logic.

This module is intentionally free of Django settings and registry state.
It receives a fully-prepared Experiment object and runs the inference pipeline.
"""
import time

import numpy as np
import torch as pt
from torch.nn.functional import one_hot

from api.exceptions import InvalidRequestError
from api.services.constants import QUERY_STRUCTURE_INTERNAL, QUERY_TREE_MAPPINGS, QUERY_STRUCTURES
from api.utils import clean_entity_name, clean_relation_name

# Research-code imports — available after settings.py adds the repos to sys.path.
from graph_completion.graphs.queries import Query, get_all_answers, get_node_cut_cache, query_edge_r_to_int
from graph_completion.graphs.preprocess import QueryData

# Step-2 mini-batch cap: the link-ranker runs a full forward pass per candidate,
# and the hit community can hold thousands of nodes on Freebase. Splitting keeps
# CPU memory bounded without changing results.
SCORING_MINI_BATCH_SIZE = 512


def coins_predict_inner(experiment, dataset_id, algorithm, query_structure_id,
                        anchors, variables, relations_map, top_k):
    """Run a single COINs query and return the CoinsPredictResponse dict.

    experiment   — fully-prepared Experiment (embedder + link_ranker + loader loaded).
    anchors      — {api_node_id: entity_id} for all anchor nodes.
    variables    — {api_node_id: entity_id} for variable nodes (may be empty).
    relations_map — {api_edge_id: relation_id} for all edges.
    top_k        — number of top predictions to return (max 10).
    """
    embedder = experiment.embedder
    link_ranker = experiment.link_ranker
    loader = experiment.loader
    device = next(embedder.parameters()).device

    qs_mapping = QUERY_TREE_MAPPINGS[query_structure_id]
    num_nodes = loader.num_nodes
    num_relations = loader.num_relations
    num_node_types = loader.num_node_types
    num_communities = loader.num_communities
    community_membership = embedder.community_membership   # PT tensor [num_nodes], long
    node_types_tensor = embedder.node_types                # PT tensor [num_nodes], long

    # Full-KG adjacency (train + val + test) — graph_indexes cover train only,
    # which would miss answers in val/test splits.
    adj_s_to_t = experiment.full_adj_s_to_t

    # ---- Build Query tree ----
    query = Query(QUERY_STRUCTURE_INTERNAL[query_structure_id])
    query.build_query_tree()
    query.get_node_cut()

    num_tree_nodes = query.query_tree.vcount()
    num_tree_edges = query.query_tree.ecount()

    # ---- Build query_instance_mapped skeleton ----
    qi_skeleton = query.query_tree.copy()
    entities_skeleton = [-1] * num_tree_nodes  # -1 = unresolved; avoids confusion with entity 0
    for api_id, entity_id in anchors.items():
        tree_idx = qs_mapping["nodes"][api_id]
        entities_skeleton[tree_idx] = int(entity_id)
    qi_skeleton.vs["e"] = entities_skeleton
    for api_id, rel_id in relations_map.items():
        edge_idx = qs_mapping["edges"][api_id]
        qi_skeleton.es[edge_idx]["r"] = f"p{rel_id}"
    # intersection edges keep "i" from build_query_tree

    # ---- Resolve variable entities ----
    _resolve_variables(qi_skeleton, query, entities_skeleton, qs_mapping,
                       variables, adj_s_to_t)

    # ---- Step 1: Community scoring ----
    t1_start = time.perf_counter()

    all_communities = pt.arange(num_communities, dtype=pt.long, device=device)
    e_c, edge_attr_c = [], []
    for i in range(num_tree_nodes):
        if i == query.query_answer:
            e_c.append(all_communities)
        else:
            com = int(community_membership[entities_skeleton[i]].item())
            e_c.append(pt.full([num_communities], com, dtype=pt.long, device=device))
    for j in range(num_tree_edges):
        r_label = qi_skeleton.es[j]["r"]
        if "p" in r_label:
            r_id = int(r_label[1:])
            edge_attr_c.append(
                one_hot(pt.full([num_communities], r_id, dtype=pt.long, device=device), num_relations + 1).float()
            )
        else:
            # intersection edge — use the "no relation" slot (index num_relations)
            edge_attr_c.append(
                one_hot(
                    pt.full([num_communities], num_relations, dtype=pt.long, device=device), num_relations + 1
                ).float()
            )

    with pt.no_grad():
        community_query = QueryData(query, e_c=e_c, edge_attr_c=edge_attr_c)
        c_q_emb, c_a_emb = embedder.embed_communities(community_query)
        community_scores = link_ranker(c_q_emb, c_a_emb, for_communities=True)

    # Sort communities by descending score for the search loop
    community_order = community_scores.argsort(descending=True)  # [K]
    step1_ms = (time.perf_counter() - t1_start) * 1000.0

    # ---- Step 2: Score every entity in the hit community ----
    # Mirrors rank_samples (experiments.py:782-786): the hit community is the
    # first one in step-1 order that contains *any* KG-valid answer; within it
    # we score all entities (minus anchors) so the link ranker actually has to
    # discriminate, instead of being handed only the known answers.
    t2_start = time.perf_counter()

    valid_answers = set(get_all_answers(qi_skeleton, query, adj_s_to_t))
    if not valid_answers:
        raise InvalidRequestError(
            "No entities in the knowledge graph satisfy this query"
        )

    anchor_entity_ids = {
        entities_skeleton[i] for i in query.query_anchors if entities_skeleton[i] != -1
    }

    rank_c = 0           # 1-based rank of the hit community (0 = no hit)
    c_err = 0            # sum of sizes of communities with better step-1 score than the hit
    community_size = 0   # size of the hit community
    candidates = []

    for rank_0indexed in range(num_communities):
        cid = int(community_order[rank_0indexed].item())
        c_entities_tensor = (community_membership == cid).nonzero(as_tuple=True)[0]
        c_size = int(c_entities_tensor.shape[0])
        c_entities = [int(e.item()) for e in c_entities_tensor]

        if any(e in valid_answers for e in c_entities):
            rank_c = rank_0indexed + 1
            community_size = c_size
            candidates = [e for e in c_entities if e not in anchor_entity_ids]
            break

        c_err += c_size

    if not candidates:
        raise InvalidRequestError(
            "No entities in the knowledge graph satisfy this query"
        )

    n_candidates = len(candidates)
    candidates_tensor = pt.tensor(candidates, dtype=pt.long, device=device)

    # Build per-tree-node entity columns. Anchor / resolved-variable positions
    # repeat the same id across the batch; the answer and phantom-i positions
    # take each candidate.
    e_batch, x_batch, c_batch, edge_attr_batch = [], [], [], []
    for i in range(num_tree_nodes):
        if entities_skeleton[i] == -1:
            entities_i = candidates_tensor
        else:
            entities_i = pt.full([n_candidates], entities_skeleton[i], dtype=pt.long, device=device)
        e_batch.append(entities_i)
        x_batch.append(one_hot(node_types_tensor[entities_i], num_node_types).float())
        c_batch.append(community_membership[entities_i])
    for j in range(num_tree_edges):
        r_label = qi_skeleton.es[j]["r"]
        if "p" in r_label:
            r_id = int(r_label[1:])
            edge_attr_batch.append(
                one_hot(pt.full([n_candidates], r_id, dtype=pt.long, device=device), num_relations + 1).float()
            )
        else:
            edge_attr_batch.append(
                one_hot(pt.full([n_candidates], num_relations, dtype=pt.long, device=device), num_relations + 1).float()
            )

    with pt.no_grad():
        batched_query = QueryData(query, e=e_batch, x=x_batch, c=c_batch, edge_attr=edge_attr_batch)
        score_chunks = []
        for chunk in batched_query.batch_split(SCORING_MINI_BATCH_SIZE):
            q_emb, a_emb = embedder(chunk)
            score_chunks.append(link_ranker(q_emb, a_emb).view(-1))
        scores = pt.cat(score_chunks)

    k = min(top_k, n_candidates)
    top_scores, top_indices = scores.topk(k)
    step2_ms = (time.perf_counter() - t2_start) * 1000.0

    # rank = c_err + intra_community_rank  (exact rank_samples formula)
    inv_nodes, _, _ = loader.dataset.get_inverted_name_maps()
    predictions = []
    for intra_community_rank, (idx, score) in enumerate(zip(top_indices.tolist(), top_scores.tolist()), 1):
        entity_id = candidates[idx]
        raw_name = str(inv_nodes.get(entity_id, entity_id))
        predictions.append({
            "intra_community_rank": intra_community_rank,
            "rank": c_err + intra_community_rank,
            "entity_id": entity_id,
            "entity_name": clean_entity_name(raw_name, dataset_id),
            "score": round(float(score), 4),
            "is_valid_answer": entity_id in valid_answers,
        })

    total_ms = step1_ms + step2_ms
    # Speedup accounts for the full search cost: K community scores + skipped communities + hit community
    speedup = num_nodes / (num_communities + c_err + community_size)
    return _build_response(dataset_id, algorithm, query_structure_id, anchors,
                           relations_map, qs_mapping, predictions, total_ms,
                           step1_ms, step2_ms, speedup, loader,
                           rank_c=rank_c, c_err=c_err)


def _resolve_variables(qi_skeleton, query, entities_skeleton, qs_mapping,
                       user_variables, adj_s_to_t):
    """Fill in unspecified variable entities via get_node_cut_cache.

    Updates qi_skeleton and entities_skeleton in-place.
    Runs up to 3 passes to handle 3p which has 2 variables.
    """
    node_api_ids = {v: k for k, v in qs_mapping["nodes"].items()}

    def _run_pass():
        cache = get_node_cut_cache(qi_skeleton, query, adj_s_to_t)
        resolved_any = False
        for tree_node_idx, candidates in cache.items():
            if tree_node_idx not in node_api_ids:
                continue
            api_id = node_api_ids[tree_node_idx]
            if entities_skeleton[tree_node_idx] != -1:
                continue  # anchor or already-resolved variable
            if api_id in user_variables:
                entity = int(user_variables[api_id])
            elif not candidates:
                raise InvalidRequestError(
                    f"No valid entity exists at variable '{api_id}' "
                    "for the given anchors and relations"
                )
            else:
                entity = int(np.random.choice(candidates))
            entities_skeleton[tree_node_idx] = entity
            qi_skeleton.vs[tree_node_idx]["e"] = entity
            resolved_any = True
        return resolved_any

    for _ in range(3):
        if not _run_pass():
            break

    # Post-processing: propagate resolved entities to nodes that get_node_cut_cache
    # can't reach (they lie between the cut and the anchors or answer in the tree).
    # Two cases:
    #  - Phantom "i" nodes (e.g. ip nodes 1,3): inherit their resolved ancestor's entity
    #  - Non-cut "p" variable nodes (e.g. 3p v1): resolve via adj_s_to_t[child_entity][rel]
    changed = True
    while changed:
        changed = False
        for i in range(query.query_tree.vcount()):
            if i == query.query_answer or entities_skeleton[i] != -1:
                continue
            in_edges = query.query_tree.es[query.query_tree.incident(i, mode="in")]
            if not in_edges:
                continue
            in_edge = in_edges[0]
            if in_edge["r"] == "i":
                # Phantom intersection node: copy the resolved parent (intersection var)
                parent = in_edge.source
                if entities_skeleton[parent] != -1:
                    entities_skeleton[i] = entities_skeleton[parent]
                    qi_skeleton.vs[i]["e"] = entities_skeleton[i]
                    changed = True
            elif "p" in in_edge["r"]:
                # Projection variable between cut and anchors: resolve from child.
                # Use qi_skeleton.es to get the concrete "p{rel_id}" label (not the
                # generic "p" from query.query_tree that would cause int("") errors).
                out_edges = qi_skeleton.es[qi_skeleton.incident(i, mode="out")]
                if out_edges:
                    child = out_edges[0].target
                    if entities_skeleton[child] != -1:
                        rel_id = query_edge_r_to_int(out_edges[0]["r"])
                        candidates = list(adj_s_to_t.get(entities_skeleton[child], {}).get(rel_id, []))
                        if not candidates:
                            api_id = node_api_ids.get(i, str(i))
                            raise InvalidRequestError(
                                f"No valid entity exists at variable '{api_id}' "
                                "for the given anchors and relations"
                            )
                        entities_skeleton[i] = int(np.random.choice(candidates))
                        qi_skeleton.vs[i]["e"] = entities_skeleton[i]
                        changed = True


def _build_response(dataset_id, algorithm, query_structure_id, anchors, relations_map,
                    qs_mapping, predictions, total_ms, step1_ms, step2_ms, speedup, loader,
                    rank_c=1, c_err=0):
    """Assemble the CoinsPredictResponse dict."""
    inv_nodes, _, inv_relations = loader.dataset.get_inverted_name_maps()

    qs_template = next(qs for qs in QUERY_STRUCTURES if qs["id"] == query_structure_id)

    # Build a name map for each node in the template
    node_name = {}
    for node in qs_template["nodes"]:
        if node["type"] == "anchor":
            raw = str(inv_nodes.get(anchors[node["id"]], anchors[node["id"]]))
            node_name[node["id"]] = clean_entity_name(raw, dataset_id)
        elif node["type"] == "variable":
            node_name[node["id"]] = "(variable)"
        else:
            node_name[node["id"]] = "?"

    # Describe each edge; comma-separate for a clean multi-pattern display
    edge_parts = []
    for edge in qs_template["edges"]:
        rel_id = relations_map[edge["id"]]
        rel = clean_relation_name(str(inv_relations.get(rel_id, rel_id)), dataset_id)
        edge_parts.append(f"{node_name[edge['source']]} --[{rel}]--> {node_name[edge['target']]}")
    query_description = ", ".join(edge_parts)

    return {
        "dataset_id": dataset_id,
        "algorithm": algorithm,
        "query_structure": query_structure_id,
        "query_description": query_description,
        "predictions": predictions,
        "timing": {
            "step1_ms": round(step1_ms, 1),
            "step1_label": "Community detection + localized embedding",
            "step2_ms": round(step2_ms, 1),
            "step2_label": "Link prediction",
            "total_ms": round(total_ms, 1),
            "rank_c": rank_c,
            "baseline_estimate_ms": round(total_ms * speedup, 1),
            "baseline_label": "Estimated baseline (without COINs)",
            "speedup": round(speedup, 2),
        },
    }