import { readFile, realpath } from "node:fs/promises";
import path from "node:path";
import { loadQxSources, resolveQxSources } from "./source-loader.js";
import {
  capabilityId,
  compileWorkspaceRevision,
  validateMigrationCatalog,
  contentDigest,
  type AtomDefinition,
  type CompiledWorkspaceRevision,
  type InterfaceRevision,
  type PackageRevision,
  type SourceRevision,
  type WorkspaceRevision,
} from "../capability-model/index.js";
import {
  loadQuixosLock,
  type GitSource,
  type LockedResource,
  type QuixosRepositoryLock,
} from "../resource-lock/index.js";
import {
  compileCapabilityResourceSource,
  compileCapabilitySource,
  type CapabilityImportEnvironment,
  type CapabilityResource,
  type CapabilityResourceImport,
} from "./parser.js";

export type CapabilityRepositorySnapshot = {
  directory: string;
};

export type CapabilityRepositoryResolver = (
  source: GitSource,
  kind: LockedResource["kind"],
) => Promise<CapabilityRepositorySnapshot>;

export type ResolvedCapabilityResource = {
  key: string;
  kind: LockedResource["kind"];
  source: GitSource;
  directory: string;
  lock: QuixosRepositoryLock;
  resource: CapabilityResource;
  dependencies: ReadonlyMap<string, ResolvedCapabilityResource>;
};

export type CompiledWorkspaceRepository = {
  workspace: WorkspaceRevision;
  plan: CompiledWorkspaceRevision;
  lock: QuixosRepositoryLock;
  resources: ResolvedCapabilityResource[];
  directResources: ReadonlyMap<string, ResolvedCapabilityResource>;
};

export type CompiledCapabilityResourceRepository = {
  resource: CapabilityResource;
  lock: QuixosRepositoryLock;
  resources: ResolvedCapabilityResource[];
  directResources: ReadonlyMap<string, ResolvedCapabilityResource>;
};

const sourceKey = (kind: LockedResource["kind"], source: GitSource) =>
  `${kind}\0${source.repository}\0${source.commit.toLowerCase()}`;

const bindingKey = (kind: LockedResource["kind"], binding: string) =>
  `${kind}\0${binding}`;

const importsKey = (entry: CapabilityResourceImport | LockedResource) =>
  bindingKey(entry.kind, entry.binding);

const assertImportsMatchLock = (
  label: string,
  imports: readonly CapabilityResourceImport[],
  resources: readonly LockedResource[],
) => {
  const authored = [...imports].map(importsKey).sort();
  const locked = [...resources].map(importsKey).sort();
  if (
    authored.length !== locked.length ||
    authored.some((entry, index) => entry !== locked[index])
  ) {
    throw new Error(
      `${label} imports do not match quixos.lock:\n` +
      `authored: ${authored.join(", ") || "none"}\n` +
      `locked: ${locked.join(", ") || "none"}`,
    );
  }
};

const exactRevisions = <Revision extends {
  revisionId: string;
  source: SourceRevision;
}>(revisions: readonly Revision[]) => {
  const seen = new Set<string>();
  return revisions.filter((revision) => {
    const key = `${revision.revisionId}\0${revision.source.repository}\0${revision.source.commit}`;
    if (seen.has(key)) return false;
    seen.add(key);
    return true;
  });
};

const exactAtoms = (atoms: readonly AtomDefinition[]) => {
  const seen = new Set<string>();
  return atoms.filter((atom) => {
    if (seen.has(atom.id)) return false;
    seen.add(atom.id);
    return true;
  });
};

const diagnosticsMessage = (
  label: string,
  diagnostics: readonly {
    fileName: string;
    line: number;
    column: number;
    phase: string;
    code: string;
    message: string;
    path?: string;
  }[],
) => `${label} did not compile:\n${diagnostics.map((entry) => {
  const location = entry.line > 0
    ? `${entry.fileName}:${entry.line}:${entry.column + 1}`
    : `${entry.fileName}${entry.path ? `:${entry.path}` : ""}`;
  return `${location}: ${entry.phase} ${entry.code}: ${entry.message}`;
}).join("\n")}`;

const revisionFor = (node: ResolvedCapabilityResource) =>
  node.resource.revision;

const resourceClosure = (
  roots: readonly ResolvedCapabilityResource[],
): ResolvedCapabilityResource[] => {
  const result: ResolvedCapabilityResource[] = [];
  const seen = new Set<string>();
  const visit = (node: ResolvedCapabilityResource) => {
    if (seen.has(node.key)) return;
    seen.add(node.key);
    for (const dependency of node.dependencies.values()) visit(dependency);
    result.push(node);
  };
  for (const root of roots) visit(root);
  return result;
};

const environmentFor = (
  direct: readonly [LockedResource, ResolvedCapabilityResource][],
  closure: readonly ResolvedCapabilityResource[],
): CapabilityImportEnvironment => ({
  interfaces: new Map(direct.flatMap(([locked, node]) =>
    node.resource.kind === "interface"
      ? [[locked.binding, node.resource.revision] as const]
      : [])),
  packages: new Map(direct.flatMap(([locked, node]) =>
    node.resource.kind === "package"
      ? [[locked.binding, node.resource.revision] as const]
      : [])),
  interfaceClosure: exactRevisions(closure.flatMap((node) =>
    node.resource.kind === "interface" ? [node.resource.revision] : [])),
  packageClosure: exactRevisions(closure.flatMap((node) =>
    node.resource.kind === "package" ? [node.resource.revision] : [])),
  externalAtoms: exactAtoms(closure.flatMap((node) => node.resource.externalAtoms)),
});

const createResourceGraphResolver = (
  quixosCommit: string,
  resolveResource: CapabilityRepositoryResolver,
) => {
  const resolved = new Map<string, Promise<ResolvedCapabilityResource>>();
  const active: string[] = [];

  const visit = async (
    locked: LockedResource,
    suppliedSnapshot?: CapabilityRepositorySnapshot,
  ): Promise<ResolvedCapabilityResource> => {
    const key = sourceKey(locked.kind, locked.source);
    const cached = resolved.get(key);
    if (cached) {
      if (active.includes(key)) {
        throw new Error(`Resource dependency cycle: ${[...active, key].join(" -> ")}`);
      }
      return await cached;
    }
    const pending = (async () => {
      active.push(key);
      try {
        const snapshot = suppliedSnapshot ?? await resolveResource(locked.source, locked.kind);
        const lockResult = await loadQuixosLock(path.join(snapshot.directory, "quixos.lock"));
        if (!lockResult.ok) {
          throw new Error(diagnosticsMessage(`${locked.kind} ${locked.binding} lock`, lockResult.diagnostics));
        }
        if (lockResult.lock.quixos.policy) {
          throw new Error(
            `${locked.kind} ${locked.binding} lock declares workspace Quixos policy ` +
            `${lockResult.lock.quixos.policy}; resource locks may only declare their exact authored-against commit`,
          );
        }
        if (lockResult.lock.quixos.commit.toLowerCase() !== quixosCommit.toLowerCase()) {
          throw new Error(
            `${locked.kind} ${locked.binding} selects Quixos ${lockResult.lock.quixos.commit}, ` +
            `but the repository graph selects ${quixosCommit}`,
          );
        }
        const directPairs: Array<[LockedResource, ResolvedCapabilityResource]> = [];
        for (const dependency of lockResult.lock.resources) {
          directPairs.push([dependency, await visit(dependency)]);
        }
        const dependencyClosure = resourceClosure(
          directPairs.map(([, node]) => node),
        );
        const environment = environmentFor(directPairs, dependencyClosure);
        const manifestName = locked.kind === "interface" ? "interface.qx" : "package.qx";
        const manifestPath = path.join(snapshot.directory, manifestName);
        const sourceText = await readFile(manifestPath, "utf8");
        const compiled = compileCapabilityResourceSource(sourceText, {
          source: locked.source,
          fileName: manifestPath,
          environment,
        });
        if (!compiled.ok) {
          throw new Error(diagnosticsMessage(`${locked.kind} ${locked.binding}`, compiled.diagnostics));
        }
        if (compiled.resource.kind !== locked.kind) {
          throw new Error(
            `${manifestPath} declares ${compiled.resource.kind}, not ${locked.kind}`,
          );
        }
        assertImportsMatchLock(manifestPath, compiled.resource.imports, lockResult.lock.resources);
        if (compiled.resource.kind === "package") {
          let catalogText: string | undefined;
          try { catalogText = await readFile(path.join(snapshot.directory, "quixos.migrations.json"), "utf8"); }
          catch (error) { if ((error as NodeJS.ErrnoException).code !== "ENOENT") throw error; }
          if (catalogText !== undefined) {
            const catalog = validateMigrationCatalog(JSON.parse(catalogText), new Set(compiled.resource.revision.exports.map((entry) => entry.id)));
            const root = await realpath(snapshot.directory);
            for (const migration of catalog.migrations) {
              const implementation = await realpath(path.join(root, migration.implementation.file));
              if (!implementation.startsWith(`${root}${path.sep}`)) throw new Error("Migration implementation escapes its package");
              if (contentDigest(await readFile(implementation, "utf8")) !== migration.implementation.digest) throw new Error(`Migration implementation digest mismatch: ${migration.id}`);
            }
            compiled.resource.revision.migrationCatalog = catalog;
          }
        }
        return {
          key,
          kind: locked.kind,
          source: locked.source,
          directory: snapshot.directory,
          lock: lockResult.lock,
          resource: compiled.resource,
          dependencies: new Map(directPairs.map(([dependency, node]) => [
            bindingKey(dependency.kind, dependency.binding),
            node,
          ])),
        };
      } finally {
        active.pop();
      }
    })();
    resolved.set(key, pending);
    return await pending;
  };

  return {
    visit,
    nodes: async () => await Promise.all(resolved.values()),
  };
};

export const compileCapabilityResourceRepository = async (options: {
  rootDirectory: string;
  kind: LockedResource["kind"];
  source: GitSource;
  resolveResource: CapabilityRepositoryResolver;
}): Promise<CompiledCapabilityResourceRepository> => {
  const lockResult = await loadQuixosLock(path.join(options.rootDirectory, "quixos.lock"));
  if (!lockResult.ok) {
    throw new Error(diagnosticsMessage("Resource lock", lockResult.diagnostics));
  }
  const resolver = createResourceGraphResolver(
    lockResult.lock.quixos.commit,
    options.resolveResource,
  );
  const root = await resolver.visit({
    kind: options.kind,
    binding: "<root>",
    source: options.source,
  }, { directory: options.rootDirectory });
  return {
    resource: root.resource,
    lock: root.lock,
    resources: await resolver.nodes(),
    directResources: root.dependencies,
  };
};

export const compileWorkspaceRepository = async (options: {
  rootDirectory: string;
  resolveResource: CapabilityRepositoryResolver;
  workspaceId?: string;
  workspaceRevisionId?: string;
  sourceRootCommit?: string;
  /** An editor's proposed source snapshot; locks and dependency revisions remain exact. */
  readSource?: (name: string) => Promise<string>;
}): Promise<CompiledWorkspaceRepository> => {
  const rootLockResult = await loadQuixosLock(
    path.join(options.rootDirectory, "quixos.lock"),
  );
  if (!rootLockResult.ok) {
    throw new Error(diagnosticsMessage("Workspace lock", rootLockResult.diagnostics));
  }
  const rootLock = rootLockResult.lock;
  const resolver = createResourceGraphResolver(rootLock.quixos.commit, options.resolveResource);

  const directPairs: Array<[LockedResource, ResolvedCapabilityResource]> = [];
  for (const locked of rootLock.resources) {
    directPairs.push([locked, await resolver.visit(locked)]);
  }
  const nodes = await resolver.nodes();
  const environment = environmentFor(directPairs, nodes);
  const workspacePath = path.join(options.rootDirectory, "workspace.qx");
  const sources = options.readSource ? await resolveQxSources(options.readSource) : await loadQxSources(options.rootDirectory);
  const compiled = compileCapabilitySource(sources.source, workspacePath, environment);
  if (!compiled.ok) {
    throw new Error(diagnosticsMessage("Workspace", compiled.diagnostics.map((diagnostic) =>
      diagnostic.line > 0 ? { ...diagnostic, ...sources.originalPosition(diagnostic.line, diagnostic.column) } : diagnostic)));
  }
  assertImportsMatchLock(workspacePath, compiled.imports, rootLock.resources);
  const availableInterfaceIds = new Set(
    nodes.flatMap((node) => node.resource.kind === "interface"
      ? [node.resource.revision.revisionId]
      : []),
  );
  const availableAtomIds = new Set(compiled.workspace.atoms.map((atom) => atom.id));
  for (const node of nodes) {
    for (const requirement of node.resource.externalInterfaces) {
      if (!availableInterfaceIds.has(requirement.revisionId)) {
        throw new Error(
          `${node.kind} ${node.resource.revision.displayName} requires external interface ` +
          `${requirement.binding} (${requirement.revisionId}), but the workspace resource graph does not provide it`,
        );
      }
    }
    for (const atom of node.resource.externalAtoms) {
      if (!availableAtomIds.has(atom.id)) {
        throw new Error(
          `${node.kind} ${node.resource.revision.displayName} requires external atom ` +
          `${atom.displayName} (${atom.id}), but the workspace does not define it`,
        );
      }
    }
  }
  const workspace: WorkspaceRevision = {
    ...compiled.workspace,
    ...(options.workspaceId
      ? { workspaceId: capabilityId.workspace(options.workspaceId) }
      : {}),
    ...(options.workspaceRevisionId
      ? { id: capabilityId.workspaceRevision(options.workspaceRevisionId) }
      : options.sourceRootCommit ? { id: capabilityId.workspaceRevision(`workspace-revision:${options.workspaceId ?? compiled.workspace.workspaceId}:${options.sourceRootCommit}`) } : {}),
    ...(options.sourceRootCommit
      ? { sourceRootCommit: options.sourceRootCommit }
      : {}),
  };
  const checked = compileWorkspaceRevision(workspace);
  if (!checked.ok) {
    throw new Error(
      `Instantiated workspace did not compile:\n${checked.issues.map((entry) =>
        `${entry.path}: ${entry.message}`).join("\n")}`,
    );
  }
  return {
    workspace,
    plan: checked.plan,
    lock: rootLock,
    resources: nodes,
    directResources: new Map(directPairs.map(([locked, node]) => [
      bindingKey(locked.kind, locked.binding),
      node,
    ])),
  };
};