import fs from "node:fs/promises";
import path from "node:path";
import {contentDigest} from "../capability-model/evolution.js";
import {validateMigrationCatalog, type MigrationCatalog, type MigrationDeclaration} from "../capability-model/migrations.js";
import {formatQuixosLock, type GitSource} from "../resource-lock/index.js";
import {parseQx, walkSyntax} from "./source.js";
import type {StructuralRequest} from "./structural-plan.js";

type Source = {repository: string; commit: string};
type Registry = {generatedBy: "qx-scaffold-v1"; name: string; id: string; revision: string; exports: {name: string; id: string; file: string; migration?: boolean}[]};
export type ScaffoldRecipe = {
  source: Source; directory?: string; name?: string; id?: string; revision?: string;
  declaration?: string;
  tools?: {quixos: Source; protocol: Source; helpers: Source; sdk: Source};
  nixifyPluginUrl?: string;
  migration?: Omit<MigrationDeclaration, "implementation"> & {contracts: Record<string, unknown>};
};
const marker = "// Generated by qx-scaffold-v1\n";
const json = (value: unknown) => `${JSON.stringify(value, null, 2)}\n`;
const source = (value: Source): GitSource => {
  const url = new URL(value.repository);
  if (url.protocol !== "https:" || url.username || url.password || url.search || url.hash || !/^(?:[0-9a-f]{40}|[0-9a-f]{64})$/.test(value.commit)) throw new Error("Scaffolds require credential-free HTTPS sources and full exact commits");
  return {resolver: "git", ...value};
};
const nixSource = (value: Source) => `git+${source(value).repository}?ref=refs/tags/quixos-reachability/${value.commit}&rev=${value.commit}`;
const nixString = (value: string) => JSON.stringify(value).replaceAll("${", "\\${");
const safeName = (name: string | undefined): string => {
  if (!name || !/^[A-Za-z_][A-Za-z0-9_]*$/.test(name)) throw new Error("Scaffold requires a simple authored name");
  return name;
};
const ownedJson = async <T>(root: string, file: string): Promise<T> => {
  const target = path.join(root, file);
  if (!(await fs.realpath(target)).startsWith(`${await fs.realpath(root)}/`)) throw new Error("Scaffold input escapes repository");
  const value = JSON.parse(await fs.readFile(target, "utf8"));
  if (value.generatedBy !== "qx-scaffold-v1") throw new Error(`Not scaffold-owned: ${file}`);
  return value;
};

/** Recipes describe structural edits; planStructure owns validation/journaling.
 * Implementation files are created once and never rewritten by refresh. */
export const scaffoldRecipe = async (root: string, command: "package" | "function" | "migration" | "refresh", spec: ScaffoldRecipe): Promise<StructuralRequest> => {
  source(spec.source);
  if (spec.directory && !/^[A-Za-z0-9_-][A-Za-z0-9_.-]*(?:\/[A-Za-z0-9_-][A-Za-z0-9_.-]*)*$/.test(spec.directory)) throw new Error("Scaffold directory must be contained");
  const prefix = spec.directory ? `${spec.directory}/` : "";
  const files: StructuralRequest["files"] = [];
  const create = (file: string, content: string) => files.push({file: prefix + file, create: content});
  const generated = (file: string, content: string) => files.push({file: prefix + file, generated: content});
  let registry: Registry;
  let catalog: MigrationCatalog & {generatedBy: "qx-scaffold-v1"};
  if (command === "package") {
    const name = safeName(spec.name);
    if (!spec.id || !spec.revision || !spec.tools) throw new Error("Package scaffold requires id, revision, and exact quixos/protocol/helpers/sdk tool sources");
    Object.values(spec.tools).forEach(source);
    registry = {generatedBy: "qx-scaffold-v1", name, id: spec.id, revision: spec.revision, exports: []};
    catalog = {generatedBy: "qx-scaffold-v1", schemaVersion: 1, contracts: {}, migrations: []};
    create("package.qx", `package ${name} id ${JSON.stringify(spec.id)} revision ${JSON.stringify(spec.revision)} {\n}\n`);
    create("quixos.lock", formatQuixosLock({formatVersion: 1, quixos: source(spec.tools.quixos), resources: []}));
    create("package.json", json({name: `@quixos/${name.toLowerCase()}`, version: "0.1.0", private: true, type: "module", packageManager: "yarn@4.18.0",
      scripts: {build: "tsc -p tsconfig.json", typecheck: "tsc --noEmit"}, dependencies: {"@quixos/camino-package-runtime": `${spec.tools.sdk.repository}#commit=${spec.tools.sdk.commit}`},
      devDependencies: {"@types/node": "^24", typescript: "^7.0.2"}}));
    create("tsconfig.json", json({compilerOptions: {target: "ES2023", module: "NodeNext", moduleResolution: "NodeNext", strict: true, outDir: "dist", skipLibCheck: true}, include: ["src/**/*.ts"]}));
    create(".gitignore", "node_modules/\ndist/\n.quixos/\nresult\n.yarn/install-state.gz\n");
    create(".yarnrc.yml", `nodeLinker: node-modules\nenableScripts: true\nnpmMinimalAgeGate: 0\napprovedGitRepositories:\n  - ${JSON.stringify(spec.tools.sdk.repository)}\nsupportedArchitectures:\n  os: [current, linux]\n  cpu: [current, x64, arm64]\n  libc: [current, glibc]\n`);
    const nixifyPluginUrl = spec.nixifyPluginUrl ?? "https://gitea-external.egads.tutti.syntaxblitz.net/quixos/yarn-plugin-nixify-patched/raw/commit/4528fdd20b30d869262443b3f044549810e75fb8/dist/yarn-plugin-nixify.js";
    const plugin = new URL(nixifyPluginUrl);
    if (plugin.protocol !== "https:" || plugin.username || plugin.password || plugin.search || plugin.hash || !/\/commit\/[a-f0-9]{40,64}\//.test(plugin.pathname)) throw new Error("Nixify plugin must have an exact credential-free HTTPS commit URL");
    generated("quixos.toolchain.json", json({generatedBy: "qx-scaffold-v1", nixifyPluginUrl}));
    create("quixos.check.json", json({backend: "typescript", bindingOutput: "src/generated-bindings.ts"}));
    create("flake.nix", `{
  inputs.protocol.url = ${nixString(nixSource(spec.tools.protocol))};
  inputs.nixpkgs.follows = "protocol/nixpkgs";
  inputs.flake-utils.follows = "protocol/flake-utils";
  inputs.helpers = { url = ${nixString(nixSource(spec.tools.helpers))}; flake = false; };
  outputs = inputs@{ self, protocol, nixpkgs, flake-utils, helpers, ... }:
    (import (toString helpers + "/quixos-package-helpers.nix")).mkCaminoTsYarnNixifyFlake {
      inherit inputs nixpkgs flake-utils; packageRoot = ./.;
      bindings = { system, ... }: {
        generator = (builtins.getAttr system protocol.packages).default;
        repository = ${nixString(spec.source.repository)};
        commit = self.rev or (throw "Publish an exact package revision before building an activation artifact");
        packageRevisionId = ${nixString(spec.revision)};
        output = "src/generated-bindings.ts";
        resources = map (entry: entry // { directory = builtins.fetchGit { url = entry.repository; rev = entry.commit; ref = "refs/tags/quixos-reachability/" + entry.commit; }; }) (builtins.fromJSON (builtins.readFile ./quixos.resources.json)).resources;
      };
      bundle = { entry = "dist/server.js"; };
      migrationEntrypoint = "dist/migrate.js";
      installServer = { libexecName = ${JSON.stringify(name.toLowerCase())}; descriptorPath = "descriptor.quixos-package.txtpb"; };
    };
}\n`);
    generated("quixos.resources.json", json({generatedBy: "qx-scaffold-v1", resources: []}));
  } else {
    registry = await ownedJson<Registry>(root, prefix + "quixos.scaffold.json");
    catalog = await ownedJson<typeof catalog>(root, prefix + "quixos.migrations.json");
    if (command !== "refresh") {
      const name = safeName(spec.name);
      if (!spec.id || registry.exports.some((entry) => entry.id === spec.id || entry.name === name)) throw new Error("New export requires a unique name and ID");
      const declaration = spec.declaration ?? `function ${name} id ${JSON.stringify(spec.id)} : unit -> unit;`;
      const parsed = parseQx(`package Scaffold id "scaffold" revision "scaffold@1" { ${declaration} }`);
      const exports = [...walkSyntax(parsed.root)].filter((node) => ["packageFunctionExport", "packageOperationExport", "packageConstructorExport"].includes(node.kind));
      if (parsed.diagnostics.length || exports.length !== 1) throw new Error("Expected one valid package export declaration");
      const wrapped = `package Scaffold id "scaffold" revision "scaffold@1" { ${declaration} }`;
      const node = exports[0];
      const derived = [...walkSyntax(node)].some((entry) => entry.kind === "eventClause");
      if (command === "migration" && (node.kind !== "packageFunctionExport" || spec.declaration)) throw new Error("Migration exports use the scaffold's unit function declaration and dedicated migration entrypoint");
      if (wrapped.slice(node.children.find((child) => child.kind === "identifier")!.start, node.children.find((child) => child.kind === "identifier")!.end) !== name
        || JSON.parse(wrapped.slice(node.children.find((child) => child.kind === "stringLiteral")!.start, node.children.find((child) => child.kind === "stringLiteral")!.end)) !== spec.id) throw new Error("Declaration name/ID must match its registration");
      files.push({file: prefix + "package.qx", edits: [{operation: "append", parent: {kind: "packageResourceDecl", id: registry.id}, source: declaration}]});
      const file = `src/${command === "migration" ? "migrations" : "impl"}/${name}.ts`;
      const implementation = command === "migration" ? `import type {MigrationContext} from "@quixos/camino-package-runtime";\nexport const handler = async (_context: MigrationContext): Promise<void> => { throw new Error(${JSON.stringify(`Implement migration ${name}`)}); };\n`
        : `import type {Implementation} from "../generated-bindings.js";\nexport const handler: Implementation[${JSON.stringify(name)}] = ${derived ? '{kind: "derived", get: ' : ""}async (_context) => { throw new Error(${JSON.stringify(`Implement ${name}`)}); }${derived ? "}" : ""};\n`;
      create(file, implementation);
      registry.exports.push({name, id: spec.id, file, ...(command === "migration" ? {migration: true} : {})});
      if (command === "migration") {
        if (!spec.migration) throw new Error("Migration scaffold requires retained contracts and an explicit transition");
        const {contracts, ...transition} = spec.migration;
        for (const [digest, contract] of Object.entries(contracts)) {
          if (contentDigest(contract) !== digest || (catalog.contracts[digest] && contentDigest(catalog.contracts[digest]) !== digest)) throw new Error("Retained migration contract mismatch");
          catalog.contracts[digest] = contract;
        }
        catalog.migrations.push({...transition, implementation: {exportId: spec.id, file, digest: contentDigest(implementation)}});
      }
    }
    if (command === "refresh") for (const migration of catalog.migrations) {
      const file = path.join(root, prefix, migration.implementation.file);
      if (!(await fs.realpath(file)).startsWith(`${await fs.realpath(path.join(root, prefix))}/`)) throw new Error("Migration implementation escapes package");
      migration.implementation.digest = contentDigest(await fs.readFile(file, "utf8"));
    }
  }
  validateMigrationCatalog(catalog, new Set(registry.exports.map((entry) => entry.id)));
  generated("quixos.scaffold.json", json(registry));
  generated("quixos.migrations.json", json(catalog));
  generated("src/server.ts", marker + `import {servePackageRuntime} from "@quixos/camino-package-runtime";\nimport {createRuntime} from "./generated-bindings.js";\n` + registry.exports.filter((entry) => !entry.migration).map((entry, index) => `import {handler as impl${index}} from ${JSON.stringify(`./${entry.file.slice(4, -3)}.js`)};\n`).join("") +
    `servePackageRuntime(createRuntime({\n` + registry.exports.map((entry) => `  ${JSON.stringify(entry.name)}: ${entry.migration ? 'async () => { throw new Error("Migration-only export"); }' : `impl${registry.exports.filter((value) => !value.migration).indexOf(entry)}`},`).join("\n") + `\n}));\n`);
  const migrations = registry.exports.filter((entry) => entry.migration);
  generated("src/migrate.ts", marker + `import {serveMigration} from "@quixos/camino-package-runtime";\n` + migrations.map((entry, index) => `import {handler as impl${index}} from ${JSON.stringify(`./${entry.file.slice(4, -3)}.js`)};\n`).join("") + `await serveMigration({${migrations.map((entry, index) => `${JSON.stringify(entry.id)}: impl${index}`).join(", ")}});\n`);
  generated("descriptor.quixos-package.txtpb", `# Generated by qx-scaffold-v1\npackage_id: ${JSON.stringify(registry.id)}\npackage_revision_id: ${JSON.stringify(registry.revision)}\nruntime_protocol_version: "quixos-capabilities-v1"\n` + registry.exports.map((entry) => `exports: { export_id: ${JSON.stringify(entry.id)} runtime_symbol: ${JSON.stringify(entry.name)} }\n`).join(""));
  return {kind: "package", source: spec.source, resourceRoot: spec.directory, files};
};