import { createHash } from "node:crypto";
import type { Binding, Conformance, DependencyBinding, PersistentAttachment, WorkspaceRevision } from "./types.js";
import { validateWorkspaceRevision } from "./validation.js";

/** Content hashing is independent of JSON object insertion order, not array order. */
const compareText = (a: string, b: string) => a < b ? -1 : a > b ? 1 : 0;
export const canonicalJson = (value: unknown): string => {
  if (value === null || typeof value === "string" || typeof value === "boolean") return JSON.stringify(value);
  if (typeof value === "number" && Number.isFinite(value)) return JSON.stringify(value);
  if (Array.isArray(value)) return `[${value.map(canonicalJson).join(",")}]`;
  if (typeof value === "object" && value !== null) {
    if (Object.getPrototypeOf(value) !== Object.prototype && Object.getPrototypeOf(value) !== null) throw new Error("Expected a plain JSON object");
    return `{${Object.entries(value).filter(([, entry]) => entry !== undefined).sort(([a], [b]) => compareText(a, b))
      .map(([key, entry]) => `${JSON.stringify(key)}:${canonicalJson(entry)}`).join(",")}}`;
  }
  throw new Error(`Cannot hash non-JSON value: ${typeof value}`);
};
export const contentDigest = (value: unknown) => `sha256:${createHash("sha256").update(canonicalJson(value)).digest("hex")}`;
const semantic = (value: unknown): unknown => {
  if (Array.isArray(value)) return value.map(semantic);
  if (value && typeof value === "object") return Object.fromEntries(Object.entries(value)
    .filter(([key, entry]) => entry !== undefined && key !== "displayName" && key !== "documentation")
    .map(([key, entry]) => [key, semantic(entry)]));
  return value;
};
const sorted = <T>(entries: readonly T[], key: (entry: T) => string) => [...entries].sort((a, b) => compareText(key(a), key(b)));
export const conformanceIdentity = (entry: Conformance): string => entry.id ?? `legacy:${entry.atomId}:${entry.interfaceRevisionId}`;

export type StorageContract = { id: string; ownerId: string; kind: "state" | "edge"; digest: string; definition: unknown };
export const storageContracts = (workspace: WorkspaceRevision): StorageContract[] => {
  const result: StorageContract[] = [];
  const add = (attachment: PersistentAttachment, ownerId: string) => {
    const definition = semantic(attachment);
    result.push({ id: attachment.id, ownerId, kind: attachment.kind, definition, digest: contentDigest({ ownerId, definition }) });
  };
  for (const attachment of workspace.sharedAttachments) add(attachment, "legacy:workspace");
  for (const conformance of workspace.conformances) for (const attachment of conformance.privateAttachments) add(attachment, conformanceIdentity(conformance));
  return sorted(result, (entry) => entry.id);
};

type GraphNode = { value: unknown; dependencies: Set<string>; reviewProviders: Set<string> };
export type RuntimeContract = { groupId: string; packageId: string; packageRevisionId: string; digest: string; reviewProviders: string[]; dependencies: Array<{ id: string; digest: string }> };

/** Build only outbound execution dependencies. Incoming callers never retain or invalidate a provider. */
export const runtimeContracts = (workspace: WorkspaceRevision): RuntimeContract[] => {
  const nodes = new Map<string, GraphNode>();
  const node = (key: string, value: unknown) => {
    const result = { value: semantic(value), dependencies: new Set<string>(), reviewProviders: new Set<string>() };
    nodes.set(key, result);
    return result;
  };
  const conformanceKey = (atom: string, iface: string) => `conformance:${atom}:${iface}`;
  for (const storage of storageContracts(workspace)) node(`attachment:${storage.id}`, storage);
  for (const iface of workspace.interfaceImports) node(`interface:${iface.revisionId}`, {
    ...iface, members: sorted(iface.members, (entry) => entry.id).map((entry) => ({ ...entry, operations: sorted(entry.operations, (operation) => operation.id) })),
  });
  for (const pkg of workspace.packageImports) node(`package:${pkg.revisionId}`, {
    ...pkg, semanticMajor: pkg.semanticMajor ?? 1,
    exports: sorted(pkg.exports, (entry) => entry.id).map((entry) => ({ ...entry, dependencyPorts: sorted(entry.dependencyPorts, (port) => port.id) })),
  });
  const dependency = (parent: GraphNode, binding: DependencyBinding, atomId: string, reviews?: Set<string>) => {
    if (binding.kind === "state") parent.dependencies.add(`attachment:${binding.slotId}`);
    if (binding.kind === "edge") parent.dependencies.add(`attachment:${binding.edgeTypeId}`);
    if (binding.kind === "constructor") {
      parent.dependencies.add(`constructor:${binding.atomId}`);
      const ctor = workspace.constructors.find((entry) => entry.atomId === binding.atomId);
      const pkg = workspace.packageImports.find((entry) => entry.revisionId === ctor?.packageRevisionId);
      if (pkg) reviews?.add(pkg.packageId);
    }
    if (binding.kind !== "constructor" && binding.via) parent.dependencies.add(`attachment:${binding.via.edgeTypeId}`);
    if (binding.kind === "interface") {
      parent.dependencies.add(`interface:${binding.interfaceRevisionId}`);
      // An edge traversal may select any matching target. Conservatively include every possible witness.
      for (const conformance of workspace.conformances) {
        if (conformance.interfaceRevisionId === binding.interfaceRevisionId && (binding.via || conformance.atomId === atomId)) {
          parent.dependencies.add(conformanceKey(conformance.atomId, conformance.interfaceRevisionId));
          reviews?.add(conformanceIdentity(conformance));
          for (const operation of conformance.operationBindings) {
            if (operation.binding.kind !== "package") continue;
            const revisionId = operation.binding.packageRevisionId;
            const pkg = workspace.packageImports.find((entry) => entry.revisionId === revisionId);
            if (pkg) reviews?.add(pkg.packageId);
          }
        }
      }
    }
  };
  const binding = (parent: GraphNode, value: Binding, atomId: string, context: unknown) => {
    if (value.kind !== "package") { dependency(parent, value, atomId); return; }
    const packageNode = nodes.get(`package:${value.packageRevisionId}`)!;
    parent.dependencies.add(`package:${value.packageRevisionId}`);
    const normalized = { ...value, dependencies: sorted(value.dependencies, (entry) => entry.portId) };
    const key = `binding:${contentDigest({ atomId, context, value: semantic(normalized) })}`;
    const bound = node(key, { atomId, context, binding: normalized });
    packageNode.dependencies.add(key);
    for (const port of value.dependencies) dependency(bound, port.binding, atomId, packageNode.reviewProviders);
  };
  for (const conformance of workspace.conformances) {
    const parent = node(conformanceKey(conformance.atomId, conformance.interfaceRevisionId), {
      id: conformanceIdentity(conformance), semanticMajor: conformance.semanticMajor ?? 1,
      atomId: conformance.atomId, interfaceRevisionId: conformance.interfaceRevisionId,
      operations: sorted(conformance.operationBindings, (entry) => entry.operationId),
      materializations: sorted(conformance.relationshipMaterializations, (entry) => entry.memberId),
    });
    parent.dependencies.add(`interface:${conformance.interfaceRevisionId}`);
    for (const attachment of conformance.privateAttachments) parent.dependencies.add(`attachment:${attachment.id}`);
    for (const operation of conformance.operationBindings) binding(parent, operation.binding, conformance.atomId, {
      conformanceId: conformanceIdentity(conformance), semanticMajor: conformance.semanticMajor ?? 1, operationId: operation.operationId,
    });
    for (const materialization of conformance.relationshipMaterializations) {
      parent.dependencies.add(`constructor:${materialization.constructorAtomId}`);
      parent.dependencies.add(`attachment:${materialization.edgeTypeId}`);
    }
  }
  for (const constructor of workspace.constructors) {
    const parent = node(`constructor:${constructor.atomId}`, constructor);
    binding(parent, { kind: "package", ...constructor }, constructor.atomId, { constructor: constructor.atomId });
  }
  const counts = new Map<string, number>();
  for (const pkg of workspace.packageImports) counts.set(pkg.packageId, (counts.get(pkg.packageId) ?? 0) + 1);
  return sorted(workspace.packageImports.map((pkg): RuntimeContract => {
    const visited = new Set<string>();
    const walk = (key: string) => {
      if (visited.has(key)) return;
      const entry = nodes.get(key);
      if (!entry) throw new Error(`Unresolved execution dependency ${key}`);
      visited.add(key);
      for (const target of entry.dependencies) walk(target);
    };
    walk(`package:${pkg.revisionId}`);
    const dependencies = [...visited].sort().map((id) => ({ id, digest: contentDigest(nodes.get(id)!.value) }));
    return { groupId: counts.get(pkg.packageId) === 1 ? pkg.packageId : `${pkg.packageId}#${pkg.revisionId}`,
      packageId: pkg.packageId, packageRevisionId: pkg.revisionId, digest: contentDigest(dependencies),
      reviewProviders: [...nodes.get(`package:${pkg.revisionId}`)!.reviewProviders].sort(), dependencies };
  }), (entry) => entry.groupId);
};

export type EvolutionReview = { requirementDigest: string; decision: "changed" | "accepted-unchanged"; rationale: string; agentId: string };
export type ReviewRequirement = { consumerId: string; providerId: string; oldMajor: number; newMajor: number; requirementDigest: string };
export type RuntimeAction = { groupId: string; action: "keep" | "start" | "replace" | "retire"; previous?: RuntimeContract; candidate?: RuntimeContract; reasons: string[] };
export type EvolutionReport = {
  schemaVersion: 1; baselineDigest: string | null; candidateDigest: string; checkerVersion: string;
  runtimeActions: RuntimeAction[];
  storageChanges: Array<{ id: string; kind: "add" | "remove" | "change"; previous?: StorageContract; candidate?: StorageContract }>;
  reviews: Array<ReviewRequirement & { accepted: boolean }>;
  packageChecks: Array<{ groupId: string; contractDigest: string }>;
  blockers: string[];
};

export const planEvolution = (baseline: WorkspaceRevision | null, candidate: WorkspaceRevision,
  options: { reviews?: EvolutionReview[]; allowLegacy?: boolean } = {}): EvolutionReport => {
  const issues = validateWorkspaceRevision(candidate);
  if (issues.length) throw new Error(`Invalid candidate workspace:\n${issues.map((entry) => `${entry.path}: ${entry.message}`).join("\n")}`);
  if (baseline && baseline.workspaceId !== candidate.workspaceId) throw new Error("Cannot evolve a different workspace");
  const candidateDigest = contentDigest(candidate);
  const checkerVersion = "quixos-evolution-v1";
  const blockers: string[] = [];
  if (!options.allowLegacy) {
    if (candidate.sharedAttachments.length) blockers.push("Assign legacy workspace-shared attachments to explicit conformance owners");
    for (const entry of candidate.conformances) if (!entry.id) blockers.push(`Conformance ${entry.atomId} as ${entry.interfaceRevisionId} requires an authored ID`);
  }
  const previousRuntimes = new Map((baseline ? runtimeContracts(baseline) : []).map((entry) => [entry.groupId, entry]));
  const nextRuntimes = new Map(runtimeContracts(candidate).map((entry) => [entry.groupId, entry]));
  const runtimeActions: RuntimeAction[] = [...new Set([...previousRuntimes.keys(), ...nextRuntimes.keys()])].sort().map((groupId) => {
    const previous = previousRuntimes.get(groupId), next = nextRuntimes.get(groupId);
    const before = new Map(previous?.dependencies.map((entry) => [entry.id, entry.digest]));
    const after = new Map(next?.dependencies.map((entry) => [entry.id, entry.digest]));
    const reasons = [...new Set([...before.keys(), ...after.keys()])].sort().filter((id) => before.get(id) !== after.get(id));
    return { groupId, action: !previous ? "start" : !next ? "retire" : previous.digest === next.digest ? "keep" : "replace",
      ...(previous ? { previous } : {}), ...(next ? { candidate: next } : {}), reasons };
  });
  const beforeStorage = new Map((baseline ? storageContracts(baseline) : []).map((entry) => [entry.id, entry]));
  const afterStorage = new Map(storageContracts(candidate).map((entry) => [entry.id, entry]));
  const storageChanges: EvolutionReport["storageChanges"] = [];
  for (const id of [...new Set([...beforeStorage.keys(), ...afterStorage.keys()])].sort()) {
    const previous = beforeStorage.get(id), next = afterStorage.get(id);
    if (previous?.digest !== next?.digest) storageChanges.push({ id, kind: !previous ? "add" : !next ? "remove" : "change",
      ...(previous ? { previous } : {}), ...(next ? { candidate: next } : {}) });
  }
  const providers = (workspace: WorkspaceRevision) => [
    ...workspace.packageImports.map((entry) => ({ id: entry.packageId as string, revision: entry.revisionId as string, major: entry.semanticMajor ?? 1,
      node: `package:${entry.revisionId}`, digest: contentDigest(entry) })),
    ...workspace.conformances.map((entry) => ({ id: conformanceIdentity(entry), revision: contentDigest(entry), major: entry.semanticMajor ?? 1,
      node: `conformance:${entry.atomId}:${entry.interfaceRevisionId}`, digest: contentDigest(entry) })),
  ];
  const oldProviders = baseline ? providers(baseline) : [];
  const reviews: EvolutionReport["reviews"] = [];
  for (const provider of providers(candidate)) {
    const old = oldProviders.filter((entry) => entry.id === provider.id);
    if (old.length > 1) { blockers.push(`Ambiguous semantic-major lineage for ${provider.id}`); continue; }
    if (!old[0] || old[0].major === provider.major) continue;
    if (provider.major < old[0].major) blockers.push(`Semantic major decreases for ${provider.id}`);
    for (const consumer of nextRuntimes.values()) {
      if (consumer.packageId === provider.id || !consumer.reviewProviders.includes(provider.id)) continue;
      const requirement = { consumerId: consumer.groupId, providerId: provider.id, oldMajor: old[0].major, newMajor: provider.major };
      const requirementDigest = contentDigest({ ...requirement, oldProvider: old[0].digest, newProvider: provider.digest, consumer: consumer.digest, checkerVersion });
      const accepted = (options.reviews ?? []).some((entry) => entry.requirementDigest === requirementDigest &&
        ["changed", "accepted-unchanged"].includes(entry.decision) && entry.rationale.trim() && entry.agentId.trim());
      reviews.push({ ...requirement, requirementDigest, accepted });
      if (!accepted) blockers.push(`Semantic-major review required: ${consumer.groupId} consumes ${provider.id}`);
    }
  }
  return { schemaVersion: 1, baselineDigest: baseline ? contentDigest(baseline) : null, candidateDigest, checkerVersion,
    runtimeActions, storageChanges, reviews, packageChecks: runtimeActions.filter((entry) => entry.candidate && entry.action !== "keep")
      .map((entry) => ({ groupId: entry.groupId, contractDigest: entry.candidate!.digest })), blockers };
};