"""
Entity-relation graph export for infospace visualisation.

Builds a graph from L2 entity classifications and L3 relation triplets,
then exports it as Mermaid or DOT format for rendering.
"""

from __future__ import annotations

from typing import Dict, List, Optional, Set, Tuple

from .classification import EntityClassification
from .relation_models import RelationMeta


# ── Color palettes ────────────────────────────────────────────────────────────

# By entity type
_TYPE_COLORS: Dict[str, str] = {
    "Element":     "#4A90D9",
    "Process":     "#27AE60",
    "Relation":    "#F39C12",
    "Principle":   "#8E44AD",
    "Institution": "#E74C3C",
    "Unknown":     "#95A5A6",
}

# By VSM system
_VSM_COLORS: Dict[str, str] = {
    "S1":  "#2ECC71",
    "S2":  "#3498DB",
    "S3":  "#E67E22",
    "S3*": "#E74C3C",
    "S4":  "#9B59B6",
    "S5":  "#1ABC9C",
}


# ── Graph data structure ──────────────────────────────────────────────────────

class EntityGraph:
    """In-memory graph of entities (nodes) and relations (edges)."""

    def __init__(self) -> None:
        # slug → dict of metadata
        self.nodes: Dict[str, dict] = {}
        # (subject_slug, object_slug) → list of edge dicts (multi-edges allowed)
        self.edges: Dict[Tuple[str, str], List[dict]] = {}
        # slugs participating in a feedback loop
        self.feedback_slugs: Set[str] = set()

    def add_node(
        self,
        slug: str,
        title: str,
        entity_type: str,
        vsm_system: str,
    ) -> None:
        self.nodes[slug] = {
            "title": title,
            "entity_type": entity_type,
            "vsm_system": vsm_system,
        }

    def add_edge(
        self,
        subject_slug: str,
        object_slug: str,
        predicate: str,
        relation_type: str,
        vsm_channel: str,
        is_feedback: bool = False,
    ) -> None:
        key = (subject_slug, object_slug)
        if key not in self.edges:
            self.edges[key] = []
        self.edges[key].append({
            "predicate": predicate,
            "relation_type": relation_type,
            "vsm_channel": vsm_channel,
            "is_feedback": is_feedback,
        })

    def subgraph_for_slugs(self, slugs: Set[str]) -> "EntityGraph":
        """Return a new EntityGraph containing only nodes in *slugs* and
        edges where BOTH endpoints are in *slugs*."""
        g = EntityGraph()
        g.feedback_slugs = self.feedback_slugs & slugs
        for s in slugs:
            if s in self.nodes:
                n = self.nodes[s]
                g.add_node(s, n["title"], n["entity_type"], n["vsm_system"])
        for (subj, obj), edge_list in self.edges.items():
            if subj in slugs and obj in slugs:
                for e in edge_list:
                    g.add_edge(subj, obj, e["predicate"], e["relation_type"],
                               e["vsm_channel"], e["is_feedback"])
        return g


# ── Builder ───────────────────────────────────────────────────────────────────

def build_entity_graph(
    classifications: List[EntityClassification],
    relations: List[RelationMeta],
    feedback_cycles: Optional[List[List[str]]] = None,
) -> EntityGraph:
    """Build an EntityGraph from L2 classifications and L3 relations.

    Args:
        classifications: All loaded EntityClassification objects.
        relations: All loaded RelationMeta objects.
        feedback_cycles: Optional list of cycles (each a list of slugs)
            returned by networkx.simple_cycles.

    Returns:
        An :class:`EntityGraph` ready for export.
    """
    g = EntityGraph()

    # Collect slugs in feedback loops
    feedback_slugs: Set[str] = set()
    if feedback_cycles:
        for cycle in feedback_cycles:
            feedback_slugs.update(cycle)
    g.feedback_slugs = feedback_slugs

    # Classify slugs for fast lookup
    cls_map: Dict[str, EntityClassification] = {c.entity_slug: c for c in classifications}

    # Add nodes from classifications
    for c in classifications:
        title = c.entity_slug.replace("_", " ").title()
        g.add_node(c.entity_slug, title, c.entity_type, c.vsm_system)

    # Add edge-referenced nodes that might not be classified
    for r in relations:
        for slug in (r.subject_slug, r.object_slug):
            if slug not in g.nodes:
                # unclassified node — add with Unknown type
                title = slug.replace("_", " ").title()
                g.add_node(slug, title, "Unknown", "")

    # Collect feedback edge pairs
    feedback_edge_pairs: Set[Tuple[str, str]] = set()
    if feedback_cycles:
        for cycle in feedback_cycles:
            for i in range(len(cycle)):
                feedback_edge_pairs.add((cycle[i], cycle[(i + 1) % len(cycle)]))

    # Add edges from relations
    for r in relations:
        is_feedback = (r.subject_slug, r.object_slug) in feedback_edge_pairs
        g.add_edge(
            r.subject_slug,
            r.object_slug,
            r.predicate,
            r.relation_type,
            r.vsm_channel,
            is_feedback=is_feedback,
        )

    return g


# ── Filters ───────────────────────────────────────────────────────────────────

def apply_filters(
    g: EntityGraph,
    filter_type: Optional[str] = None,
    filter_vsm: Optional[str] = None,
    filter_entity: Optional[str] = None,
    loops_only: bool = False,
    classified_only: bool = True,
    classified_slugs: Optional[Set[str]] = None,
) -> EntityGraph:
    """Apply filters to an EntityGraph, returning a subgraph.

    Filtering strategy:
    - Start with all node slugs in the graph.
    - Remove unclassified if classified_only (Unknown type = unclassified placeholder).
    - If filter_type: keep only nodes with matching entity_type.
    - If filter_vsm: keep only nodes with matching vsm_system.
    - If filter_entity: keep only that entity plus its direct neighbors (via edges).
    - If loops_only: keep only nodes participating in feedback loops.
    - Finally include both endpoints of every edge that survives the filter.
    """
    # Start with classified-only filter
    candidate_slugs: Set[str] = set(g.nodes.keys())

    if classified_only and classified_slugs is not None:
        candidate_slugs &= classified_slugs

    if filter_type:
        candidate_slugs = {
            s for s in candidate_slugs
            if g.nodes[s]["entity_type"].lower() == filter_type.lower()
        }

    if filter_vsm:
        candidate_slugs = {
            s for s in candidate_slugs
            if g.nodes[s]["vsm_system"].lower() == filter_vsm.lower()
        }

    if loops_only:
        candidate_slugs &= g.feedback_slugs

    if filter_entity:
        if filter_entity not in g.nodes:
            return EntityGraph()
        # Ego subgraph: entity + direct neighbors
        neighbors: Set[str] = {filter_entity}
        for (subj, obj) in g.edges:
            if subj == filter_entity:
                neighbors.add(obj)
            elif obj == filter_entity:
                neighbors.add(subj)
        candidate_slugs &= neighbors

    # Expand candidate_slugs to include all edge endpoints that survive
    # (so we don't create dangling edges)
    final_slugs: Set[str] = set()
    for (subj, obj) in g.edges:
        if subj in candidate_slugs and obj in candidate_slugs:
            final_slugs.add(subj)
            final_slugs.add(obj)

    # If filter_entity used, keep at minimum the entity itself even if no edges
    if filter_entity and filter_entity in g.nodes:
        final_slugs.add(filter_entity)

    # If we removed all edges but still have type/vsm filter nodes, show those
    if not final_slugs and candidate_slugs:
        final_slugs = candidate_slugs

    return g.subgraph_for_slugs(final_slugs)


# ── Mermaid export ────────────────────────────────────────────────────────────

def _mermaid_safe_id(slug: str) -> str:
    """Return a Mermaid-safe node ID (replace special chars)."""
    return slug.replace("-", "_").replace("*", "s")


def to_mermaid(
    g: EntityGraph,
    color_by: str = "type",
    markdown_fence: bool = True,
) -> str:
    """Export an EntityGraph to Mermaid flowchart format.

    Args:
        g: The graph to render.
        color_by: ``"type"`` or ``"vsm"`` — determines node colour scheme.
        markdown_fence: Wrap output in a ```mermaid fenced code block
            (required for VS Code and GitHub markdown preview).

    Returns:
        A Mermaid diagram string, optionally wrapped in a markdown fence.
    """
    lines: List[str] = ["graph LR"]

    # Nodes
    for slug, attrs in sorted(g.nodes.items()):
        mid = _mermaid_safe_id(slug)
        title = attrs["title"]
        etype = attrs["entity_type"]
        vsm = attrs["vsm_system"]

        label_parts = [title]
        if etype and etype != "Unknown":
            label_parts.append(f"{etype}")
        if vsm:
            label_parts.append(vsm)
        label = "\\n".join(label_parts)

        css_class = etype.lower().replace("*", "s") if etype else "unknown"
        lines.append(f'    {mid}["{label}"]:::{css_class}')

    lines.append("")

    # Edges — always use "-- label -->" syntax (robust with parentheses/special chars).
    # Feedback loop edges use "== label ==>" (thick arrow) to distinguish them visually.
    for (subj, obj), edge_list in sorted(g.edges.items()):
        smid = _mermaid_safe_id(subj)
        omid = _mermaid_safe_id(obj)
        for e in edge_list:
            pred = e["predicate"]
            if e["is_feedback"]:
                lines.append(f"    {smid} == {pred} ==> {omid}")
            else:
                lines.append(f"    {smid} -- {pred} --> {omid}")

    lines.append("")

    # Class definitions
    if color_by == "vsm":
        for vsm, color in _VSM_COLORS.items():
            css_id = vsm.lower().replace("*", "s")
            lines.append(f"    classDef {css_id} fill:{color},color:#fff")
        lines.append("    classDef unknown fill:#95A5A6,color:#fff")
    else:
        for etype, color in _TYPE_COLORS.items():
            css_id = etype.lower()
            lines.append(f"    classDef {css_id} fill:{color},color:#fff")

    body = "\n".join(lines) + "\n"
    if markdown_fence:
        return f"```mermaid\n{body}```\n"
    return body


# ── DOT export ────────────────────────────────────────────────────────────────

def _dot_safe_id(slug: str) -> str:
    """Return a DOT-safe node ID."""
    return '"' + slug.replace('"', '\\"') + '"'


def to_dot(
    g: EntityGraph,
    color_by: str = "type",
) -> str:
    """Export an EntityGraph to Graphviz DOT format.

    Args:
        g: The graph to render.
        color_by: ``"type"`` or ``"vsm"`` — determines node fill colour.

    Returns:
        A DOT digraph string.
    """
    lines: List[str] = [
        "digraph entity_graph {",
        "    rankdir=LR;",
        "    node [style=filled, fontname=Helvetica, fontsize=10];",
        "    edge [fontname=Helvetica, fontsize=9];",
        "",
    ]

    for slug, attrs in sorted(g.nodes.items()):
        nid = _dot_safe_id(slug)
        title = attrs["title"]
        etype = attrs["entity_type"]
        vsm = attrs["vsm_system"]

        if color_by == "vsm":
            color = _VSM_COLORS.get(vsm, "#95A5A6")
        else:
            color = _TYPE_COLORS.get(etype, "#95A5A6")

        label_parts = [title]
        if etype and etype != "Unknown":
            label_parts.append(f"({etype})")
        if vsm:
            label_parts.append(vsm)
        label = "\\n".join(label_parts)

        lines.append(f'    {nid} [label="{label}", fillcolor="{color}", fontcolor="white"];')

    lines.append("")

    for (subj, obj), edge_list in sorted(g.edges.items()):
        sid = _dot_safe_id(subj)
        oid = _dot_safe_id(obj)
        for e in edge_list:
            pred = e["predicate"].replace('"', '\\"')
            style = "dashed" if e["is_feedback"] else "solid"
            lines.append(f'    {sid} -> {oid} [label="{pred}", style={style}];')

    lines.append("}")
    return "\n".join(lines) + "\n"