"""Accumulate explanatory investigation paths and generate Mermaid deterministically."""
import re
from app.domain.domain_errors import require
from app.domain.schemas.operational_task import (
    InvestigationDiagram, InvestigationDiagramNodeRef, InvestigationGraphUpdate,
)


def _label(value: str) -> str:
    # Encode Mermaid delimiters and HTML before placing untrusted text in quotes.
    replacements = {"#": "#35;", "&": "#38;", '"': "#quot;", "<": "#lt;",
                    ">": "#gt;", "`": "#96;", "%": "#37;", "|": "#124;", "\\": "#92;"}
    return "".join(replacements.get(c, " " if c in "\r\n" else c) for c in value)


def adopt_legacy_investigation_graph(diagram: InvestigationDiagram) -> InvestigationDiagram:
    """Make a saved legacy graph cumulative without parsing or changing its source."""
    if diagram.edges is not None:
        return diagram
    return diagram.model_copy(deep=True, update={"edges": [], "source_mermaid": diagram.mermaid})


def update_investigation_graph(
    previous: InvestigationDiagram | None, update: InvestigationGraphUpdate,
) -> InvestigationDiagram:
    """Upsert nodes and append explicit edges; never delete a path or erase a failed attempt.

    A retry uses a new node id. Relationships describe activity for readers and
    impose no ordering or completion requirements on the Agent.
    """
    if previous is not None:
        previous = adopt_legacy_investigation_graph(previous)
    source = previous.source_mermaid if previous else None
    def in_source(node_id: str) -> bool:
        return bool(source and re.search(
            rf"(?<![A-Za-z0-9_-]){re.escape(node_id)}(?=\s*(?:[\[({{@;]|:::|--|==|-\.|$))",
            source, re.MULTILINE,
        ))

    nodes = {node.node_id: node.model_copy(deep=True) for node in previous.node_refs} if previous else {}
    require(len({node.node_id for node in update.nodes}) == len(update.nodes),
            "GRAPH_NODE_DUPLICATE", "Graph update contains duplicate node ids", status=422)
    for node in update.nodes:
        require(node.node_id.lower() not in {"end", "graph", "flowchart", "subgraph"},
                "GRAPH_NODE_ID_INVALID", "Use a descriptive graph node id", status=422)
        existing = nodes.get(node.node_id)
        if existing is None:
            require(not in_source(node.node_id), "GRAPH_LEGACY_NODE_CONFLICT",
                    "This id belongs to the original Mermaid; use a new node id", status=409)
            nodes[node.node_id] = InvestigationDiagramNodeRef.model_validate(node.model_dump(exclude_unset=True))
            continue
        require(not in_source(node.node_id) or existing.label == node.label,
                "GRAPH_LEGACY_NODE_CONFLICT", "Keep the original node label; use a new node for a new step", status=409)
        require(existing.status != "failed" or (
            ("status" not in node.model_fields_set or node.status == "failed")
            and existing.label == node.label
        ), "GRAPH_FAILED_ATTEMPT_IMMUTABLE", "Keep the failed attempt; use a new node for a retry", status=409)
        changes = node.model_dump(exclude_unset=True)
        if existing.status == "failed" and existing.detail and not changes.get("detail"):
            changes.pop("detail", None)
        for field in ("evidence_refs", "action_refs", "map_targets"):
            combined = list(getattr(existing, field))
            for value in getattr(node, field):
                if value not in combined:
                    combined.append(value)
            changes[field] = combined
        nodes[node.node_id] = InvestigationDiagramNodeRef.model_validate({
            **existing.model_dump(), **changes,
        })
    require(bool(nodes), "GRAPH_NODE_REQUIRED", "Add a node before publishing a graph", status=422)
    edges = list(previous.edges or []) if previous else []
    for edge in update.edges:
        require(edge.source in nodes and edge.target in nodes, "GRAPH_EDGE_NODE_NOT_FOUND",
                "Every graph edge must reference saved or newly added nodes", status=422)
        if edge not in edges:
            edges.append(edge.model_copy(deep=True))
    require(len(nodes) <= 100 and len(edges) <= 200, "GRAPH_CAPACITY_EXCEEDED",
            "Investigation graph exceeds 100 nodes or 200 edges; existing paths were retained", status=422)
    lines = [source or "flowchart TD"]
    for node in nodes.values():
        if in_source(node.node_id):
            continue  # Preserve original branches, shapes and labels byte for byte.
        label = node.label + ("（失败）" if node.status == "failed" else "")
        lines.append(f'  {node.node_id}["{_label(label)}"]')
    for edge in edges:
        connector = f' -->|"{_label(edge.label)}"| ' if edge.label else " --> "
        lines.append(f"  {edge.source}{connector}{edge.target}")
    mermaid = "\n".join(lines)
    require(len(mermaid) <= 20000, "GRAPH_CAPACITY_EXCEEDED",
            "Investigation Mermaid exceeds 20000 characters; existing paths were retained", status=422)
    return InvestigationDiagram(
        title=update.title or (previous.title if previous else "调查脉络"),
        mermaid=mermaid, node_refs=list(nodes.values()), edges=edges, source_mermaid=source,
    )