import { describe, it, expect } from "vitest";
import { FlowGraph } from "../../src/graph/construction.js";
import {
  topologicalOrder,
  hasCycles,
  findCycles,
  ancestors,
  descendants,
  reachableFrom,
} from "../../src/graph/queries.js";
import { CycleError, NodeNotFoundError } from "../../src/error/index.js";
import type { DirectedGraph } from "graphology";

function buildDiamondDag(): FlowGraph {
  const fg = new FlowGraph();
  fg.addNode("top", { name: "top" });
  fg.addNode("left", { name: "left" });
  fg.addNode("right", { name: "right" });
  fg.addNode("bottom", { name: "bottom" });
  fg.addEdge("top", "left");
  fg.addEdge("top", "right");
  fg.addEdge("left", "bottom");
  fg.addEdge("right", "bottom");
  return fg;
}

function buildChainDag(): FlowGraph {
  const fg = new FlowGraph();
  fg.addNode("a", { name: "a" });
  fg.addNode("b", { name: "b" });
  fg.addNode("c", { name: "c" });
  fg.addNode("d", { name: "d" });
  fg.addEdge("a", "b");
  fg.addEdge("b", "c");
  fg.addEdge("c", "d");
  return fg;
}

describe("FlowGraph topologicalOrder", () => {
  it("returns topological order for a chain", () => {
    const fg = buildChainDag();
    const order = fg.topologicalOrder();
    expect(order).toEqual(["a", "b", "c", "d"]);
  });

  it("returns topological order for a diamond DAG", () => {
    const fg = buildDiamondDag();
    const order = fg.topologicalOrder();
    expect(order[0]).toBe("top");
    expect(order[3]).toBe("bottom");
    expect(order).toContain("left");
    expect(order).toContain("right");
  });

  it("returns empty array for empty graph", () => {
    const fg = new FlowGraph();
    expect(fg.topologicalOrder()).toEqual([]);
  });

  it("returns single node for graph with one node", () => {
    const fg = new FlowGraph();
    fg.addNode("only", { name: "only" });
    expect(fg.topologicalOrder()).toEqual(["only"]);
  });

  it("throws CycleError when graph has cycles (via raw graph access)", () => {
    const fg = new FlowGraph();
    fg.addNode("a", { name: "a" });
    fg.addNode("b", { name: "b" });
    fg._edgeKey;
    fg.graph.addNode("c");
    fg.graph.addEdgeWithKey("a->b", "a", "b");
    fg.graph.addEdgeWithKey("b->c", "b", "c");
    fg.graph.addEdgeWithKey("c->a", "c", "a");
    expect(() => fg.topologicalOrder()).toThrow(CycleError);
  });
});

describe("FlowGraph hasCycles", () => {
  it("returns false for a DAG", () => {
    const fg = buildDiamondDag();
    expect(fg.hasCycles()).toBe(false);
  });

  it("returns false for empty graph", () => {
    const fg = new FlowGraph();
    expect(fg.hasCycles()).toBe(false);
  });

  it("returns false for a chain", () => {
    const fg = buildChainDag();
    expect(fg.hasCycles()).toBe(false);
  });

  it("returns true when graph has cycles (via raw graph)", () => {
    const fg = new FlowGraph();
    fg.graph.addNode("a");
    fg.graph.addNode("b");
    fg.graph.addEdgeWithKey("a->b", "a", "b");
    fg.graph.addEdgeWithKey("b->a", "b", "a");
    expect(fg.hasCycles()).toBe(true);
  });
});

describe("FlowGraph findCycles", () => {
  it("returns empty array for a DAG", () => {
    const fg = buildDiamondDag();
    expect(fg.findCycles()).toEqual([]);
  });

  it("returns empty array for empty graph", () => {
    const fg = new FlowGraph();
    expect(fg.findCycles()).toEqual([]);
  });

  it("finds a simple cycle (via raw graph)", () => {
    const fg = new FlowGraph();
    fg.graph.addNode("a");
    fg.graph.addNode("b");
    fg.graph.addEdgeWithKey("a->b", "a", "b");
    fg.graph.addEdgeWithKey("b->a", "b", "a");
    const cycles = fg.findCycles();
    expect(cycles.length).toBeGreaterThan(0);
    expect(cycles[0]!.length).toBeGreaterThan(0);
  });

  it("finds a three-node cycle (via raw graph)", () => {
    const fg = new FlowGraph();
    fg.graph.addNode("a");
    fg.graph.addNode("b");
    fg.graph.addNode("c");
    fg.graph.addEdgeWithKey("a->b", "a", "b");
    fg.graph.addEdgeWithKey("b->c", "b", "c");
    fg.graph.addEdgeWithKey("c->a", "c", "a");
    const cycles = fg.findCycles();
    expect(cycles.length).toBeGreaterThan(0);
  });
});

describe("FlowGraph ancestors", () => {
  it("returns all ancestors for a node in a chain", () => {
    const fg = buildChainDag();
    expect(fg.ancestors("d")).toEqual(["c", "b", "a"]);
  });

  it("returns all ancestors for a node in a diamond DAG", () => {
    const fg = buildDiamondDag();
    const anc = fg.ancestors("bottom");
    expect(anc).toContain("left");
    expect(anc).toContain("right");
    expect(anc).toContain("top");
    expect(anc.length).toBe(3);
  });

  it("returns empty array for a root node", () => {
    const fg = buildChainDag();
    expect(fg.ancestors("a")).toEqual([]);
  });

  it("returns empty array for a node in a graph with no edges", () => {
    const fg = new FlowGraph();
    fg.addNode("a", { name: "a" });
    fg.addNode("b", { name: "b" });
    expect(fg.ancestors("a")).toEqual([]);
  });

  it("throws NodeNotFoundError for missing node", () => {
    const fg = new FlowGraph();
    expect(() => fg.ancestors("missing")).toThrow(NodeNotFoundError);
  });
});

describe("FlowGraph descendants", () => {
  it("returns all descendants for a node in a chain", () => {
    const fg = buildChainDag();
    expect(fg.descendants("a")).toEqual(["b", "c", "d"]);
  });

  it("returns all descendants for a node in a diamond DAG", () => {
    const fg = buildDiamondDag();
    const desc = fg.descendants("top");
    expect(desc).toContain("left");
    expect(desc).toContain("right");
    expect(desc).toContain("bottom");
    expect(desc.length).toBe(3);
  });

  it("returns only direct and transitive children from left in diamond", () => {
    const fg = buildDiamondDag();
    const desc = fg.descendants("left");
    expect(desc).toEqual(["bottom"]);
  });

  it("returns empty array for a leaf node", () => {
    const fg = buildChainDag();
    expect(fg.descendants("d")).toEqual([]);
  });

  it("throws NodeNotFoundError for missing node", () => {
    const fg = new FlowGraph();
    expect(() => fg.descendants("missing")).toThrow(NodeNotFoundError);
  });
});

describe("FlowGraph reachableFrom", () => {
  it("returns all reachable nodes from a single start node", () => {
    const fg = buildChainDag();
    const reachable = fg.reachableFrom(["a"]);
    expect(reachable).toEqual(new Set(["a", "b", "c", "d"]));
  });

  it("returns only the start node if it's a leaf", () => {
    const fg = buildChainDag();
    const reachable = fg.reachableFrom(["d"]);
    expect(reachable).toEqual(new Set(["d"]));
  });

  it("returns union of reachable nodes from multiple start nodes", () => {
    const fg = buildDiamondDag();
    const reachable = fg.reachableFrom(["left", "right"]);
    expect(reachable).toEqual(new Set(["left", "right", "bottom"]));
  });

  it("returns empty set for empty input", () => {
    const fg = buildChainDag();
    expect(fg.reachableFrom([])).toEqual(new Set());
  });

  it("skips nodes that don't exist in graph", () => {
    const fg = buildChainDag();
    const reachable = fg.reachableFrom(["a", "missing"]);
    expect(reachable).toEqual(new Set(["a", "b", "c", "d"]));
  });
});

describe("FlowGraph filterByStatus", () => {
  it("returns node keys with matching status", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", { requestId: "r1", operationId: "op1", status: "running" });
    fg.addNode("r2", { requestId: "r2", operationId: "op2", status: "completed" });
    fg.addNode("r3", { requestId: "r3", operationId: "op3", status: "running" });
    expect(fg.filterByStatus("running").sort()).toEqual(["r1", "r3"]);
    expect(fg.filterByStatus("completed")).toEqual(["r2"]);
  });

  it("returns empty array when no nodes match", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", { requestId: "r1", operationId: "op1", status: "pending" });
    expect(fg.filterByStatus("failed")).toEqual([]);
  });

  it("returns empty array for empty graph", () => {
    const fg = new FlowGraph();
    expect(fg.filterByStatus("pending")).toEqual([]);
  });
});

describe("FlowGraph getRoots", () => {
  it("returns top-level call nodes", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", { requestId: "r1", operationId: "op1", status: "running" });
    fg.addNode("r2", { requestId: "r2", operationId: "op2", status: "pending", parentRequestId: "r1" });
    fg.addNode("r3", { requestId: "r3", operationId: "op3", status: "completed" });
    const roots = fg.getRoots().sort();
    expect(roots).toEqual(["r1", "r3"]);
  });

  it("returns all nodes if none have parentRequestId", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", { requestId: "r1", operationId: "op1", status: "pending" });
    fg.addNode("r2", { requestId: "r2", operationId: "op2", status: "pending" });
    const roots = fg.getRoots().sort();
    expect(roots).toEqual(["r1", "r2"]);
  });

  it("returns empty array for empty graph", () => {
    const fg = new FlowGraph();
    expect(fg.getRoots()).toEqual([]);
  });
});

describe("FlowGraph children", () => {
  it("returns direct children via triggered edges", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", { requestId: "r1", operationId: "op1", status: "running" });
    fg.addNode("r2", { requestId: "r2", operationId: "op2", status: "pending" });
    fg.addNode("r3", { requestId: "r3", operationId: "op3", status: "pending" });
    fg.graph.addEdgeWithKey("r1->r2", "r1", "r2", { edgeType: "triggered" });
    fg.graph.addEdgeWithKey("r1->r3", "r1", "r3", { edgeType: "triggered" });
    const children = fg.children("r1").sort();
    expect(children).toEqual(["r2", "r3"]);
  });

  it("excludes non-triggered edges", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", { requestId: "r1", operationId: "op1", status: "running" });
    fg.addNode("r2", { requestId: "r2", operationId: "op2", status: "pending" });
    fg.graph.addEdgeWithKey("r1->r2", "r1", "r2", { edgeType: "depends_on" });
    expect(fg.children("r1")).toEqual([]);
  });

  it("returns empty array for a leaf node", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", { requestId: "r1", operationId: "op1", status: "pending" });
    expect(fg.children("r1")).toEqual([]);
  });

  it("throws NodeNotFoundError for missing node", () => {
    const fg = new FlowGraph();
    expect(() => fg.children("missing")).toThrow(NodeNotFoundError);
  });
});

describe("FlowGraph duration", () => {
  it("returns duration in milliseconds", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", {
      requestId: "r1",
      operationId: "op1",
      status: "completed",
      startedAt: "2026-01-01T00:00:00.000Z",
      completedAt: "2026-01-01T00:00:05.000Z",
    });
    expect(fg.duration("r1")).toBe(5000);
  });

  it("returns 0 for simultaneous start and end", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", {
      requestId: "r1",
      operationId: "op1",
      status: "completed",
      startedAt: "2026-01-01T00:00:00.000Z",
      completedAt: "2026-01-01T00:00:00.000Z",
    });
    expect(fg.duration("r1")).toBe(0);
  });

  it("throws if startedAt is missing", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", {
      requestId: "r1",
      operationId: "op1",
      status: "running",
      completedAt: "2026-01-01T00:00:05.000Z",
    });
    expect(() => fg.duration("r1")).toThrow();
  });

  it("throws if completedAt is missing", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", {
      requestId: "r1",
      operationId: "op1",
      status: "running",
      startedAt: "2026-01-01T00:00:00.000Z",
    });
    expect(() => fg.duration("r1")).toThrow();
  });

  it("throws NodeNotFoundError for missing node", () => {
    const fg = new FlowGraph();
    expect(() => fg.duration("missing")).toThrow(NodeNotFoundError);
  });
});

describe("FlowGraph lineage", () => {
  it("returns ancestor chain from root to node", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", { requestId: "r1", operationId: "op1", status: "completed" });
    fg.addNode("r2", { requestId: "r2", operationId: "op2", status: "completed", parentRequestId: "r1" });
    fg.addNode("r3", { requestId: "r3", operationId: "op3", status: "running", parentRequestId: "r2" });
    expect(fg.lineage("r3")).toEqual(["r1", "r2", "r3"]);
  });

  it("returns single element for root node", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", { requestId: "r1", operationId: "op1", status: "completed" });
    expect(fg.lineage("r1")).toEqual(["r1"]);
  });

  it("stops if parentRequestId node does not exist in graph", () => {
    const fg = new FlowGraph();
    fg.addNode("r1", { requestId: "r1", operationId: "op1", status: "running", parentRequestId: "r0" });
    expect(fg.lineage("r1")).toEqual(["r1"]);
  });

  it("throws NodeNotFoundError for missing node", () => {
    const fg = new FlowGraph();
    expect(() => fg.lineage("missing")).toThrow(NodeNotFoundError);
  });
});

describe("standalone topologicalOrder", () => {
  it("returns topological order for a graph", () => {
    const fg = buildChainDag();
    expect(topologicalOrder(fg.graph)).toEqual(["a", "b", "c", "d"]);
  });
});

describe("standalone hasCycles", () => {
  it("returns false for DAG", () => {
    const fg = buildChainDag();
    expect(hasCycles(fg.graph)).toBe(false);
  });
});

describe("standalone findCycles", () => {
  it("returns empty for DAG", () => {
    const fg = buildChainDag();
    expect(findCycles(fg.graph)).toEqual([]);
  });
});

describe("standalone ancestors", () => {
  it("returns ancestors for a node", () => {
    const fg = buildChainDag();
    expect(ancestors(fg.graph, "d")).toEqual(["c", "b", "a"]);
  });
});

describe("standalone descendants", () => {
  it("returns descendants for a node", () => {
    const fg = buildChainDag();
    expect(descendants(fg.graph, "a")).toEqual(["b", "c", "d"]);
  });
});

describe("standalone reachableFrom", () => {
  it("returns all reachable nodes", () => {
    const fg = buildDiamondDag();
    const result = reachableFrom(fg.graph, ["top"]);
    expect(result).toEqual(new Set(["top", "left", "right", "bottom"]));
  });

  it("returns union from multiple starts", () => {
    const fg = buildDiamondDag();
    const result = reachableFrom(fg.graph, ["left", "right"]);
    expect(result).toEqual(new Set(["left", "right", "bottom"]));
  });
});