"""
rules/deployment_rules.py
--------------------------
Decides *which* services are active and how they relate to each other,
based on a user's InfraConfig. This module contains no rendering logic
(no Jinja2, no YAML, no Mermaid syntax) — it only answers questions like
"what does the request path look like?" and "what should the security
report flag?". Generators consume these decisions and render them into
their respective formats.
"""

from __future__ import annotations

from dataclasses import dataclass, field
from typing import Literal

from utils.config import InfraConfig

NodeKind = Literal["entry", "network", "compute", "cache", "database", "vector", "monitoring", "cicd"]


@dataclass(frozen=True)
class ServiceNode:
    """A single box in the architecture graph."""

    id: str
    label: str
    kind: NodeKind


@dataclass(frozen=True)
class ServiceEdge:
    """A connection between two ServiceNodes."""

    source: str
    target: str
    style: Literal["solid", "dashed"] = "solid"
    label: str = ""


@dataclass(frozen=True)
class ArchitectureGraph:
    nodes: list[ServiceNode] = field(default_factory=list)
    edges: list[ServiceEdge] = field(default_factory=list)


def build_architecture_graph(config: InfraConfig) -> ArchitectureGraph:
    """
    Build the full architecture graph (nodes + edges) for a given config.

    Main request path (always present, top to bottom):
        Client -> Load Balancer -> Deployment Target -> App Framework

    Then, only if the user selected them (i.e. not "None"), each data
    service connects DIRECTLY from App Framework — as independent,
    parallel dependencies, not a chain:
        App Framework -> Cache
        App Framework -> Database
        App Framework -> Vector Database
    (A prior version chained these off each other — App -> Cache ->
    Database -> Vector Database — which is topologically wrong: it
    implies, for example, that the vector database sits between the app
    and the relational database. Since this graph feeds both the Mermaid
    diagram and the ArchitectureAdvisor's prompt, that wrong shape was
    visible in the diagram and could mislead the AI's reasoning about the
    actual request path.)

    Side branches (dashed, since they're not on the live request path):
        App Framework -> Monitoring
        CI/CD -> Deployment Target   (deploy pipeline, not user traffic)
    """
    nodes: list[ServiceNode] = [
        ServiceNode("client", "Client", "entry"),
        ServiceNode("lb", "Load Balancer", "network"),
        ServiceNode("deploy_target", config.deployment_target, "compute"),
        ServiceNode("app", config.app_framework, "compute"),
    ]
    edges: list[ServiceEdge] = [
        ServiceEdge("client", "lb"),
        ServiceEdge("lb", "deploy_target"),
        ServiceEdge("deploy_target", "app"),
    ]

    # Data-layer dependencies — each is an independent, parallel child of
    # "app", only wired in if the user actually chose one. Order in this
    # tuple only affects node/edge list ordering (cosmetic), not topology.
    for field_value, node_id, kind in (
        (config.cache, "cache", "cache"),
        (config.database, "database", "database"),
        (config.vector_db, "vector_db", "vector"),
    ):
        if field_value and field_value != "None":
            nodes.append(ServiceNode(node_id, field_value, kind))
            edges.append(ServiceEdge("app", node_id))

    # Side branches
    if config.monitoring and config.monitoring != "None":
        nodes.append(ServiceNode("monitoring", config.monitoring, "monitoring"))
        edges.append(ServiceEdge("app", "monitoring", style="dashed", label="metrics"))

    if config.cicd and config.cicd != "None":
        nodes.append(ServiceNode("cicd", config.cicd, "cicd"))
        edges.append(ServiceEdge("cicd", "deploy_target", style="dashed", label="deploy"))

    return ArchitectureGraph(nodes=nodes, edges=edges)


def active_data_services(config: InfraConfig) -> list[str]:
    """
    Convenience helper for generators that just need the list of active
    data-layer services (used by docker_generator / kubernetes_generator
    in later steps to decide which containers/manifests to emit).
    """
    services = []
    if config.cache and config.cache != "None":
        services.append(config.cache)
    if config.database and config.database != "None":
        services.append(config.database)
    if config.vector_db and config.vector_db != "None":
        services.append(config.vector_db)
    return services


def high_availability_requested(config: InfraConfig) -> bool:
    """Single source of truth for HA branching across generators."""
    return config.high_availability