import {
  EMPTY_MODULE_SECRET_SOURCE,
  isSupportedConfigurationUrl,
  MODULE_CONFIGURATION_VALUE_MAX_LENGTH,
  type ModuleConfiguration,
  type ModuleConfigurationBlockedReason,
  type ModuleConfigurationValue,
  type ModuleSecretSource,
} from "@ekklesia/contracts";
import type { ReadonlyModuleManifest } from "./discovery.js";

/**
 * One declaration exactly as discovery hands it over: deeply frozen, so an `enum`'s `values` arrive
 * as a `readonly string[]`. Derived from the manifest type rather than restated, so a change to the
 * declaration contract becomes a compile error here instead of a silently divergent second copy.
 */
type DiscoveredConfigurationDeclaration = ReadonlyModuleManifest["configuration"][number];

/**
 * One persisted configuration value, exactly as it is stored: an owning module, a key, and an
 * **unparsed text literal**.
 *
 * The value is text rather than a typed column or a JSON document on purpose. Every declared type
 * has one canonical text form, values are small and bounded, and — most importantly — keeping the
 * stored form untyped makes "a persisted value is never silently trusted" structural rather than
 * aspirational: nothing can read this as a number until it has been validated against the module's
 * own current declaration.
 */
export interface ModuleConfigurationRecord {
  readonly moduleId: string;
  readonly key: string;
  readonly value: string;
}

/** The complete stored configuration for every module anyone has ever configured. */
export interface ModuleConfigurationSettings {
  readonly records: readonly ModuleConfigurationRecord[];
}

/** Everything resolution needs that Core cannot derive from a manifest: what an operator stored,
 * and what the deployment supplies for secrets. */
export interface ModuleConfigurationInput {
  readonly settings: ModuleConfigurationSettings;
  /** Defaults to supplying nothing, so a caller that provides no secrets says so by omission and a
   * module requiring one is reported `secret_missing` rather than silently starting without it. */
  readonly secrets?: ModuleSecretSource;
}

/** Why one module's configuration could not be resolved, naming the offending key. Never the value:
 * a key is public (it is declared in an installed manifest), a value may be a credential. */
export interface ModuleConfigurationIssue {
  readonly reason: ModuleConfigurationBlockedReason;
  readonly key: string;
}

export interface ResolvedModuleConfiguration {
  /** The frozen snapshot the module receives, present only when every declared requirement was
   * satisfied. */
  readonly configuration?: ModuleConfiguration;
  /** The first unsatisfied requirement, in declaration order, or `undefined` when resolution
   * succeeded. Reporting one rather than all of them matches how a blocked dependency is reported:
   * an operator fixes the named problem and re-runs, and a list of cascading complaints from one
   * missing value would be noise. */
  readonly issue?: ModuleConfigurationIssue;
  /** Stored keys this module's *current* manifest no longer declares. Retained by the store and
   * ignored here — never an error, never passed to the module. Surfaced so an operator can see that
   * a downgrade or a renamed key left something behind. */
  readonly unknownKeys: readonly string[];
}

/**
 * The module-facing snapshot, built over a `Map`.
 *
 * A `Map` rather than a plain object is deliberate and load-bearing: every lookup key here
 * originates in a module's manifest, and indexing a plain object with such a key is the exact shape
 * of a prototype-pollution bug. With a `Map` there is no prototype to reach, so `constructor` or
 * `__proto__` would be ordinary absent keys even if the contract's own reserved-name check were
 * ever removed.
 */
function createModuleConfiguration(
  values: ReadonlyMap<string, { readonly type: string; readonly value: ModuleConfigurationValue }>,
): ModuleConfiguration {
  const sortedKeys = Object.freeze([...values.keys()].sort());
  const typed = (key: string, type: string): ModuleConfigurationValue | undefined => {
    const entry = values.get(key);
    // Fails closed identically for an undeclared key and a declared key of another type, in the
    // same style as `PermissionRegistry.get`: a caller can never distinguish "you did not declare
    // this" from "you declared it as something else", and neither one silently returns a value.
    return entry?.type === type ? entry.value : undefined;
  };
  return Object.freeze({
    get: (key: string): ModuleConfigurationValue | undefined => values.get(key)?.value,
    getBoolean: (key: string): boolean | undefined => {
      const value = typed(key, "boolean");
      return typeof value === "boolean" ? value : undefined;
    },
    getEnum: (key: string): string | undefined => {
      const value = typed(key, "enum");
      return typeof value === "string" ? value : undefined;
    },
    getInteger: (key: string): number | undefined => {
      const value = typed(key, "integer");
      return typeof value === "number" ? value : undefined;
    },
    getSecret: (key: string): string | undefined => {
      const value = typed(key, "secret");
      return typeof value === "string" ? value : undefined;
    },
    getString: (key: string): string | undefined => {
      const value = typed(key, "string");
      return typeof value === "string" ? value : undefined;
    },
    getUrl: (key: string): string | undefined => {
      const value = typed(key, "url");
      return typeof value === "string" ? value : undefined;
    },
    has: (key: string): boolean => values.has(key),
    keys: (): readonly string[] => sortedKeys,
  });
}

/**
 * Parses one stored text literal against its declaration, or reports that it does not satisfy it.
 *
 * Never coerces, truncates, rounds, or falls back to the default: a stored value that does not
 * validate is an operator-visible error, not something to quietly repair. `"7 "`, `"07"`, `"yes"`,
 * and `"1"` are all rejected for the types where they are not the canonical form, so exactly one
 * spelling of any value is ever accepted and two deployments can never resolve the same stored row
 * differently.
 */
function parseStoredValue(
  declaration: DiscoveredConfigurationDeclaration,
  raw: string,
): ModuleConfigurationValue | undefined {
  if (raw.length > MODULE_CONFIGURATION_VALUE_MAX_LENGTH) {
    return undefined;
  }
  switch (declaration.type) {
    case "string": {
      if (declaration.minLength !== undefined && raw.length < declaration.minLength) {
        return undefined;
      }
      if (declaration.maxLength !== undefined && raw.length > declaration.maxLength) {
        return undefined;
      }
      return raw;
    }
    case "integer": {
      if (!/^-?(?:0|[1-9]\d*)$/u.test(raw)) {
        return undefined;
      }
      const parsed = Number(raw);
      if (!Number.isSafeInteger(parsed)) {
        return undefined;
      }
      if (declaration.minimum !== undefined && parsed < declaration.minimum) {
        return undefined;
      }
      if (declaration.maximum !== undefined && parsed > declaration.maximum) {
        return undefined;
      }
      return parsed;
    }
    case "boolean": {
      return raw === "true" ? true : raw === "false" ? false : undefined;
    }
    case "enum": {
      return declaration.values.includes(raw) ? raw : undefined;
    }
    case "url": {
      return isSupportedConfigurationUrl(raw) ? raw : undefined;
    }
    case "secret": {
      // Unreachable: a secret is never read from storage, and the store refuses to write one. The
      // branch exists so adding a type to the union is a compile error here rather than a silent
      // acceptance of persisted secret material.
      return undefined;
    }
  }
}

/**
 * Resolves one module's complete configuration from its own manifest declarations, the operator's
 * stored values, and the deployment's secrets.
 *
 * Pure and synchronous: no database, no filesystem, no `process.env`, no clock, and no module code.
 * It is handed everything it needs and returns either a frozen snapshot or the first unsatisfied
 * requirement, so every rule below is testable without PostgreSQL.
 *
 * ## Precedence, exactly
 *
 * 1. A stored value that validates against the current declaration wins.
 * 2. A stored value that does **not** validate is `configuration_invalid` — never replaced by the
 *    default, because silently falling back would run the module on a value nobody chose while the
 *    operator believes theirs took effect.
 * 3. Otherwise the declared `default` applies, if there is one.
 * 4. Otherwise a `required` key is `configuration_missing` (or `secret_missing`), and an optional
 *    key is simply absent.
 *
 * Secrets never participate in steps 1–3: they are never stored and never defaulted, so a secret is
 * whatever the deployment supplies, or missing.
 *
 * ## Keys the manifest no longer declares
 *
 * Ignored, and retained by the store. A stored key the current manifest does not declare is exactly
 * the situation a module downgrade or a renamed key produces, and deleting the row would destroy an
 * operator's value on a temporary rollback — the same reasoning ADR 0027 applied to a Dashboard
 * placement for an uninstalled module.
 */
export function resolveModuleConfigurationFor(
  manifest: ReadonlyModuleManifest,
  input: ModuleConfigurationInput,
): ResolvedModuleConfiguration {
  const secrets = input.secrets ?? EMPTY_MODULE_SECRET_SOURCE;
  const declarations = manifest.configuration;
  const declaredKeys = new Set(declarations.map((declaration) => declaration.key));
  const stored = new Map<string, string>();
  for (const record of input.settings.records) {
    if (record.moduleId === manifest.id) {
      stored.set(record.key, record.value);
    }
  }
  const unknownKeys = Object.freeze(
    [...stored.keys()].filter((key) => !declaredKeys.has(key)).sort(),
  );

  const values = new Map<string, { type: string; value: ModuleConfigurationValue }>();
  for (const declaration of declarations) {
    if (declaration.type === "secret") {
      // Scoped by construction: the source is asked for this module's id and a key that module's
      // own manifest declares. There is no call shape that reaches another module's secret, and no
      // way to ask the host for an arbitrary environment variable.
      const supplied = secrets.get(manifest.id, declaration.key);
      if (typeof supplied === "string" && supplied.length > 0) {
        values.set(declaration.key, { type: "secret", value: supplied });
        continue;
      }
      if (declaration.required) {
        return Object.freeze({
          issue: Object.freeze({ key: declaration.key, reason: "secret_missing" as const }),
          unknownKeys,
        });
      }
      continue;
    }

    const raw = stored.get(declaration.key);
    if (raw !== undefined) {
      const parsed = parseStoredValue(declaration, raw);
      if (parsed === undefined) {
        return Object.freeze({
          issue: Object.freeze({ key: declaration.key, reason: "configuration_invalid" as const }),
          unknownKeys,
        });
      }
      values.set(declaration.key, { type: declaration.type, value: parsed });
      continue;
    }

    if (declaration.default !== undefined) {
      values.set(declaration.key, { type: declaration.type, value: declaration.default });
      continue;
    }

    if (declaration.required) {
      return Object.freeze({
        issue: Object.freeze({ key: declaration.key, reason: "configuration_missing" as const }),
        unknownKeys,
      });
    }
  }

  return Object.freeze({ configuration: createModuleConfiguration(values), unknownKeys });
}

/**
 * The environment variable one module's declared secret is read from, in an Ekklesia deployment.
 *
 * `EKKLESIA_MODULE_SECRET__<MODULE_ID>__<KEY>`, with the module id's kebab-case and the key's
 * camelCase each folded to `UPPER_SNAKE`. A double underscore separates the three parts so a single
 * underscore inside a converted name can never make two different (module, key) pairs collide.
 *
 * **A module never sees this name.** It calls `config.getSecret("storageCredential")`; the mapping
 * is entirely the host's, which is exactly what lets a standalone host read the same declared secret
 * from a YAML file or a secret manager without the module's feature code changing (ADR 0029).
 */
export function moduleSecretEnvironmentVariableName(moduleId: string, key: string): string {
  const upperSnake = (value: string): string =>
    value
      .replace(/-/gu, "_")
      .replace(/([a-z0-9])([A-Z])/gu, "$1_$2")
      .toUpperCase();
  return `EKKLESIA_MODULE_SECRET__${upperSnake(moduleId)}__${upperSnake(key)}`;
}

/**
 * A secret source backed by a deployment's environment.
 *
 * Takes the environment **as an argument** rather than reading `process.env` itself, preserving the
 * repository rule that reusable Core code never touches the process environment — only executables
 * do (`core/src/cli/database-transport-environment.ts` states the same rule for database
 * transport). It is also what makes this trivially testable without mutating global state.
 *
 * There is deliberately no method that takes an arbitrary variable name. The only reachable values
 * are those a module declared as `secret` in its own manifest, looked up under a name this function
 * derives — a module cannot read `DATABASE_URL`, another module's secret, or anything else about
 * the host.
 */
export function createEnvironmentModuleSecretSource(
  environment: Readonly<Record<string, string | undefined>>,
): ModuleSecretSource {
  return Object.freeze({
    get: (moduleId: string, key: string): string | undefined =>
      environment[moduleSecretEnvironmentVariableName(moduleId, key)],
  });
}