import { Prisma } from '../../../generated/prisma';
import type { AutomationTriggerType } from '../../../generated/prisma';
import { assertTransactionClient, type DbClient } from '../../prisma/db-client';
import { lockRowForUpdate } from '../../prisma/row-lock';
import { DEFAULT_RULES } from './default-rules';
import { ruleConfigOf } from './rule-config.registry';
import type { RuleConfigMap } from './rule-config.types';

export interface ActiveRule<K extends AutomationTriggerType> {
  /** null while no row exists yet: the built-in setting applies. */
  id: string | null;
  active: boolean;
  config: RuleConfigMap[K];
  actionTemplate: string | null;
}

interface RuleRow {
  id: string;
  active: boolean;
  config: Prisma.JsonValue;
  actionTemplate: string | null;
}

const RULE_COLUMNS = {
  id: true,
  active: true,
  config: true,
  actionTemplate: true,
} as const;

function toActiveRule<K extends AutomationTriggerType>(
  trigger: K,
  row: RuleRow | null,
): ActiveRule<K> {
  if (row === null) {
    const defaults = DEFAULT_RULES[trigger];
    return {
      id: null,
      active: defaults.active ?? true,
      config: ruleConfigOf(trigger, defaults.config),
      actionTemplate: defaults.actionTemplate,
    };
  }
  return {
    id: row.id,
    active: row.active,
    config: ruleConfigOf(trigger, row.config),
    actionTemplate: row.actionTemplate,
  };
}

/**
 * The rule as it is in force: its row, or the built-in setting while there is
 * none. The config is parsed, so every key is valid.
 */
export async function readRule<K extends AutomationTriggerType>(
  db: DbClient,
  trigger: K,
): Promise<ActiveRule<K>> {
  const row = await db.automationRule.findUnique({
    where: { triggerType: trigger },
    select: RULE_COLUMNS,
  });
  return toActiveRule(trigger, row);
}

/**
 * Creates the rule row if it is missing (without touching an existing one),
 * locks it until the transaction ends and reads it. Serialises everything
 * that decides "is there already an open task/suggestion" under the rule.
 */
export async function lockRuleIn<K extends AutomationTriggerType>(
  tx: Prisma.TransactionClient,
  trigger: K,
): Promise<ActiveRule<K> & { id: string }> {
  assertTransactionClient(tx, 'lockRuleIn');
  const defaults = DEFAULT_RULES[trigger];
  await tx.automationRule.createMany({
    data: [
      {
        triggerType: trigger,
        active: defaults.active ?? true,
        config: defaults.config as Prisma.InputJsonValue,
        actionTemplate: defaults.actionTemplate,
      },
    ],
    skipDuplicates: true,
  });
  const { id } = await tx.automationRule.findUniqueOrThrow({
    where: { triggerType: trigger },
    select: { id: true },
  });
  await lockRowForUpdate(tx, 'AutomationRule', id);
  // Read after the lock: a concurrent edit of the rule is visible now.
  const row = await tx.automationRule.findUniqueOrThrow({
    where: { id },
    select: RULE_COLUMNS,
  });
  return { ...toActiveRule(trigger, row), id };
}