import { constants, realpathSync, statSync, accessSync } from "node:fs";
import { isAbsolute, relative } from "node:path";
import { buildInstallationContract, type InstallationRole, type InstallationSuffix } from "./contracts.js";
import {
  DWH_TRANSPORTS,
  VECTOR_TRANSPORTS,
  validateCanonicalWorkspace,
  type DwhTransport,
  type VectorTransport,
  type WorkspaceDescriptor,
} from "./schema.js";

export interface RuntimeBindings {
  dwh: ResolvedBinding;
  vector: ResolvedBinding;
  vectorWriter: ResolvedBinding;
  embedding: ResolvedBinding;
}

export interface ResolvedBinding {
  transport: DwhTransport | VectorTransport;
  values: Record<string, string>;
  missing: string[];
}

const REQUIRED_SUFFIXES: Record<"DWH" | "VECTOR", Record<string, readonly InstallationSuffix[]>> = {
  DWH: {
    postgres_direct: ["HOST", "PORT", "USER", "PASSWORD_FILE"],
    rest_api: ["BASE_URL", "API_KEY_FILE"],
    ssh_tunnel: [
      "USER", "PASSWORD_FILE", "SSH_HOST", "SSH_PORT", "SSH_USER",
      "SSH_PRIVATE_KEY_FILE", "SSH_KNOWN_HOSTS_FILE", "SSH_TARGET_HOST", "SSH_TARGET_PORT",
    ],
  },
  VECTOR: {
    pgvector_direct: ["HOST", "PORT", "USER", "PASSWORD_FILE"],
    rest_api: ["BASE_URL", "API_KEY_FILE"],
    ssh_tunnel: [
      "USER", "PASSWORD_FILE", "SSH_HOST", "SSH_PORT", "SSH_USER",
      "SSH_PRIVATE_KEY_FILE", "SSH_KNOWN_HOSTS_FILE", "SSH_TARGET_HOST", "SSH_TARGET_PORT",
    ],
  },
};

const EMBEDDING_REQUIRED_SUFFIXES: readonly InstallationSuffix[] = ["BASE_URL"];

function isTransport(value: string | undefined): value is DwhTransport | VectorTransport {
  return value !== undefined
    && ([...DWH_TRANSPORTS, ...VECTOR_TRANSPORTS] as readonly string[]).includes(value);
}

function isInside(path: string, root: string): boolean {
  const pathRelative = relative(root, path);
  return pathRelative !== "" && !pathRelative.startsWith("..") && !isAbsolute(pathRelative);
}

function isSafeSecretFile(path: string, secretRoots: readonly string[]): boolean {
  if (!isAbsolute(path)) return false;

  try {
    const resolvedPath = realpathSync(path);
    const resolvedRoots = secretRoots.map((root) => realpathSync(root));
    if (!resolvedRoots.some((root) => isInside(resolvedPath, root))) return false;
    if (!statSync(resolvedPath).isFile()) return false;
    accessSync(resolvedPath, constants.R_OK);
    return true;
  } catch {
    return false;
  }
}

function requiredSuffixes(
  workspace: WorkspaceDescriptor,
  role: InstallationRole,
  transport: DwhTransport | VectorTransport,
): readonly InstallationSuffix[] {
  if (role === "EMBEDDING") return EMBEDDING_REQUIRED_SUFFIXES;
  if (role === "VECTOR_WRITER") return ["API_KEY_FILE"];
  const required = REQUIRED_SUFFIXES[role][transport] ?? [];
  const diagnostic = role === "DWH"
    ? workspace.diagnostics?.dwh_rest
    : workspace.diagnostics?.vector_rest?.metadata;
  return transport === "rest_api" && diagnostic?.auth === "none"
    ? required.filter((suffix) => suffix !== "API_KEY_FILE")
    : required;
}

/**
 * Resolve only installation-local values. Secret files remain file paths: their contents are
 * deliberately left for the harness secret-file loader, so bindings cannot leak credentials.
 */
export function resolveBinding(
  workspace: WorkspaceDescriptor,
  role: InstallationRole,
  env: NodeJS.ProcessEnv,
  secretRoots: readonly string[],
): ResolvedBinding {
  const canonical = validateCanonicalWorkspace(workspace);
  const contract = buildInstallationContract(canonical);
  const variables = contract.variables.filter((variable) => variable.role === role);
  const transportVariable = variables.find((variable) => variable.suffix === "TRANSPORT");
  const supported = role === "DWH"
    ? canonical.dwh.supported_transports
    : role === "VECTOR"
      ? canonical.semantic_index.vector_store.supported_transports
      : ["rest_api"] as const;
  const selectedValue = transportVariable ? env[transportVariable.name] : undefined;
  const selectedTransport = isTransport(selectedValue) ? selectedValue : supported[0];
  const missing: string[] = [];

  if (transportVariable && (!isTransport(selectedValue) || !supported.includes(selectedTransport as never))) {
    missing.push(transportVariable.name);
  }

  const required = new Set(requiredSuffixes(canonical, role, selectedTransport));
  const values: Record<string, string> = {};
  for (const variable of variables) {
    if (variable.suffix === "TRANSPORT") continue;
    if (variable.transports && !variable.transports.includes(selectedTransport as never)) continue;

    const value = env[variable.name];
    const present = value !== undefined && value.trim() !== "";
    const safe = !variable.secret || (present && isSafeSecretFile(value, secretRoots));
    if ((required.has(variable.suffix) && !present) || (present && !safe)) {
      missing.push(variable.name);
    }
    if (present && safe) values[variable.name] = value;
  }

  return { transport: selectedTransport, values, missing };
}

/** Resolve all runtime roles together so optional writer credentials cannot be smuggled into reader bindings. */
export function resolveRuntimeBindings(
  workspace: WorkspaceDescriptor,
  env: NodeJS.ProcessEnv,
  secretRoots: readonly string[],
): RuntimeBindings {
  return {
    dwh: resolveBinding(workspace, "DWH", env, secretRoots),
    vector: resolveBinding(workspace, "VECTOR", env, secretRoots),
    vectorWriter: resolveBinding(workspace, "VECTOR_WRITER", env, secretRoots),
    embedding: resolveBinding(workspace, "EMBEDDING", env, secretRoots),
  };
}