/**
 * Step-runner — invoked by the worker scheduler when a delayed
 * `email-sequence.step` job wakes up.
 *
 * Responsibilities:
 *   1. Load run + delivery rows.
 *   2. Skip / cancel based on run status (unsubscribe / cancellation
 *      mid-sequence).
 *   3. Evaluate per-step conditions against the cached payload.
 *   4. Render template via injected `templateRenderer` → { html, text }.
 *   5. Call injected `mailSender` to send the email with the
 *      List-Unsubscribe header. Persist providerMessageId.
 *   6. Advance the run (next step or completion) via {@link advanceSequenceRun}.
 *
 * Storage + queue surfaces are injected so the runner is fully unit-testable.
 */

import type { SequenceRunRow, SequenceEngineStore, SequenceEngineQueue, SequenceEngineLogger, StepDeliveryStatus } from "./engine.js";
import { advanceSequenceRun } from "./engine.js";
import type { SequenceStep, SequenceTriggerContext } from "./types.js";
import { evaluateAllConditions } from "./conditions.js";

export interface RenderedMail {
  readonly html: string;
  readonly text: string;
  readonly subject: string;
}

export interface MailSendResult {
  readonly ok: boolean;
  readonly messageId?: string;
  readonly errorTag?: string;
  readonly bounced?: boolean;
}

export interface StepRunnerStore extends SequenceEngineStore {
  loadRun(runId: string): Promise<SequenceRunRow | null>;
  loadSteps(runId: string): Promise<readonly SequenceStep[]>;
  loadTriggerContext(runId: string): Promise<SequenceTriggerContext | null>;
  /** Atomically transition the delivery row to a terminal status. */
  markDelivery(args: {
    runId: string;
    stepIndex: number;
    status: StepDeliveryStatus;
    sentAt?: Date;
    bouncedAt?: Date;
    errorMessage?: string;
    providerMessageId?: string;
  }): Promise<void>;
}

export interface StepRunnerDeps {
  readonly store: StepRunnerStore;
  readonly queue: SequenceEngineQueue;
  readonly logger?: SequenceEngineLogger;
  readonly now?: () => Date;
  readonly renderTemplate: (
    step: SequenceStep,
    trigger: SequenceTriggerContext,
    runId: string
  ) => Promise<RenderedMail> | RenderedMail;
  readonly sendMail: (input: {
    to: string;
    subject: string;
    html: string;
    text: string;
    unsubscribeUrl: string;
    listUnsubscribeMailto?: string;
  }) => Promise<MailSendResult>;
  readonly buildUnsubscribeUrl: (trigger: SequenceTriggerContext, runId: string) => string;
  readonly buildUnsubscribeMailto?: (trigger: SequenceTriggerContext, runId: string) => string | undefined;
}

export interface StepRunResult {
  readonly action: "sent" | "skipped" | "failed" | "cancelled";
  readonly completed: boolean;
}

export async function runStep(
  args: { runId: string; stepIndex: number },
  deps: StepRunnerDeps
): Promise<StepRunResult> {
  const run = await deps.store.loadRun(args.runId);
  if (!run) {
    deps.logger?.warn?.({ op: "sequence.step.run_missing", runId: args.runId }, "sequence run not found");
    return { action: "cancelled", completed: true };
  }
  if (run.status === "cancelled" || run.status === "unsubscribed" || run.status === "completed" || run.status === "failed") {
    deps.logger?.info?.(
      { op: "sequence.step.run_inactive", runId: args.runId, status: run.status },
      "sequence run inactive — skip"
    );
    return { action: "cancelled", completed: true };
  }

  const steps = await deps.store.loadSteps(args.runId);
  const step = steps.find((s) => s.stepIndex === args.stepIndex);
  if (!step) {
    deps.logger?.warn?.(
      { op: "sequence.step.unknown_step", runId: args.runId, stepIndex: args.stepIndex },
      "step index out of range"
    );
    return { action: "cancelled", completed: true };
  }

  const trigger = await deps.store.loadTriggerContext(args.runId);
  if (!trigger) {
    deps.logger?.warn?.(
      { op: "sequence.step.no_trigger", runId: args.runId },
      "trigger context missing — skip"
    );
    await deps.store.markDelivery({
      runId: args.runId,
      stepIndex: args.stepIndex,
      status: "skipped",
      errorMessage: "trigger_context_missing",
    });
    const adv = await advanceSequenceRun(
      { run, steps, previousStepIndex: args.stepIndex },
      { store: deps.store, queue: deps.queue, logger: deps.logger, now: deps.now }
    );
    return { action: "skipped", completed: adv.completed };
  }

  if (!evaluateAllConditions(trigger.payload, step.conditions)) {
    deps.logger?.info?.(
      { op: "sequence.step.conditions_false", runId: args.runId, stepIndex: args.stepIndex },
      "step conditions not met — skip"
    );
    await deps.store.markDelivery({
      runId: args.runId,
      stepIndex: args.stepIndex,
      status: "skipped",
    });
    const adv = await advanceSequenceRun(
      { run, steps, previousStepIndex: args.stepIndex },
      { store: deps.store, queue: deps.queue, logger: deps.logger, now: deps.now }
    );
    return { action: "skipped", completed: adv.completed };
  }

  const rendered = await deps.renderTemplate(step, trigger, args.runId);
  const unsubscribeUrl = deps.buildUnsubscribeUrl(trigger, args.runId);
  const listUnsubscribeMailto = deps.buildUnsubscribeMailto?.(trigger, args.runId);
  const result = await deps.sendMail({
    to: trigger.email,
    subject: rendered.subject,
    html: rendered.html,
    text: rendered.text,
    unsubscribeUrl,
    listUnsubscribeMailto,
  });
  const sentAt = (deps.now ?? (() => new Date()))();
  if (result.ok) {
    await deps.store.markDelivery({
      runId: args.runId,
      stepIndex: args.stepIndex,
      status: "sent",
      sentAt,
      providerMessageId: result.messageId,
    });
    deps.logger?.info?.(
      { op: "sequence.step.sent", runId: args.runId, stepIndex: args.stepIndex, providerMessageId: result.messageId },
      "sequence step sent"
    );
    const adv = await advanceSequenceRun(
      { run, steps, previousStepIndex: args.stepIndex },
      { store: deps.store, queue: deps.queue, logger: deps.logger, now: deps.now }
    );
    return { action: "sent", completed: adv.completed };
  }
  if (result.bounced) {
    await deps.store.markDelivery({
      runId: args.runId,
      stepIndex: args.stepIndex,
      status: "bounced",
      bouncedAt: sentAt,
      errorMessage: result.errorTag,
    });
    await deps.store.updateRunStatus(args.runId, "failed", sentAt);
    deps.logger?.warn?.(
      { op: "sequence.step.bounced", runId: args.runId, stepIndex: args.stepIndex, errorTag: result.errorTag },
      "sequence step bounced — run failed"
    );
    return { action: "failed", completed: true };
  }
  await deps.store.markDelivery({
    runId: args.runId,
    stepIndex: args.stepIndex,
    status: "failed",
    errorMessage: result.errorTag,
  });
  deps.logger?.error(
    { op: "sequence.step.failed", runId: args.runId, stepIndex: args.stepIndex, errorTag: result.errorTag },
    "sequence step send failed"
  );
  return { action: "failed", completed: false };
}