import type { Logger, ServiceHandle } from "@dispatch/kernel";
import { defineService } from "@dispatch/kernel";
import type { SessionOrchestrator } from "@dispatch/session-orchestrator";
import type {
  HeartbeatConfig,
  HeartbeatRun,
  StopHeartbeatRunResponse,
  UpdateHeartbeatRequest,
} from "@dispatch/transport-contract";
import { createHeartbeatConfigStore, type HeartbeatConfigStore } from "./config-store.js";
import { createHeartbeatRunStore, type HeartbeatRunStore } from "./run-store.js";
import { HeartbeatScheduler, realTimers, type Timers } from "./scheduler.js";

/**
 * The dedicated workspace heartbeat-spawned conversations are filed in (NOT the
 * configured workspace). The config + run history stay per-workspace (tracked
 * under the configured workspaceId); only the spawned conversation's PLACEMENT
 * moves here, so heartbeat conversations don't clog the configured workspace's
 * tabs. The orchestrator auto-creates this workspace on first fire (via
 * `ensureWorkspace`), so it appears on the workspaces home page like any other.
 */
export const HEARTBEAT_WORKSPACE_ID = "heartbeat";

/**
 * The heartbeat service surface — what transport-http consumes and what the
 * extension wires into the host.
 */
export interface HeartbeatService {
  /** The per-workspace heartbeat config (defaults when never set). */
  readonly getConfig: (workspaceId: string) => Promise<HeartbeatConfig>;
  /**
   * Apply a partial config update. Side effect: arms/disarms the scheduler
   * for this workspace (enabled → schedule; disabled → stop). Returns the new
   * config.
   */
  readonly updateConfig: (
    workspaceId: string,
    update: UpdateHeartbeatRequest,
  ) => Promise<HeartbeatConfig>;
  /** Heartbeat runs for a workspace, most-recent first. */
  readonly listRuns: (workspaceId: string) => Promise<readonly HeartbeatRun[]>;
  /**
   * The server-authoritative next-fire time for a workspace's heartbeat, as
   * an ISO 8601 string — the moment the scheduler will fire the next run
   * (the last run's completion + `intervalMinutes`, or the moment `enabled`
   * was toggled on + `intervalMinutes` for the first run). `null` when the
   * heartbeat is disabled/disarmed, or when a run is in flight and the next
   * hasn't been queued yet (no countdown to show). A cheap read of the
   * scheduler's pending fire time.
   */
  readonly nextRunAt: (workspaceId: string) => Promise<string | null>;
  /**
   * Stop an in-flight run (abort its turn). Idempotent for an already-finished
   * run. Throws when the run id is unknown (→ HTTP 404).
   */
  readonly stopRun: (workspaceId: string, runId: string) => Promise<StopHeartbeatRunResponse>;
  /** Boot: sweep stale runs + arm every enabled workspace's scheduler. */
  readonly startAll: () => Promise<void>;
  /** Shutdown: stop every scheduler. */
  readonly stopAll: () => void;
}

/** Typed service handle the heartbeat extension provides and transport consumes. */
export const heartbeatServiceHandle: ServiceHandle<HeartbeatService> =
  defineService<HeartbeatService>("heartbeat");

export interface HeartbeatServiceDeps {
  /** Namespaced storage (from `host.storage("heartbeat")`). */
  readonly storage: import("@dispatch/kernel").StorageNamespace;
  /** The session orchestrator (drives heartbeat turns). */
  readonly orchestrator: SessionOrchestrator;
  readonly logger?: Logger;
  /** Injectable timers (default: real). */
  readonly timers?: Timers;
  /** Injectable id generator (default: crypto.randomUUID). */
  readonly generateId?: () => string;
  /**
   * Resolve `[type:name]` variable placeholders in a prompt template against
   * the current environment — the SAME resolver + variable catalog the global
   * system-prompt template uses (system/file/prompt/git groups). Applied once
   * per run, when the turn is constructed (mirrors the global template's
   * construct-once-per-conversation resolution). When omitted, templates pass
   * through UNRESOLVED (raw) — the extension wires the real resolver; tests
   * inject a fake.
   */
  readonly resolvePrompt?: (
    template: string,
    ctx: {
      readonly workspaceId: string;
      readonly conversationId: string;
      readonly model: string;
    },
  ) => Promise<string>;
  /**
   * Resolve an empty heartbeat `systemPrompt` to the GLOBAL system prompt
   * template — the same one `GET /system-prompt` returns / that regular
   * conversations resolve. Applied ONLY when the heartbeat's persisted
   * `systemPrompt` is `""` (inherit), and BEFORE variable resolution
   * (`resolvePrompt` / CR-HB-1) runs on the result, so both apply in order:
   * empty ⇒ global template, then `[type:name]` placeholders resolved. A
   * non-empty `systemPrompt` is an explicit override and bypasses this.
   * When omitted, empty stays empty (no system prompt) — the extension
   * wires the real getter; tests inject a fake.
   */
  readonly getGlobalSystemPrompt?: () => Promise<string>;
  /**
   * The configured workspace's `defaultCwd` (or `null` when the workspace has
   * none). Used to pin the heartbeat turn's cwd to the CONFIGURED workspace's
   * directory — NOT the heartbeat workspace's (empty) defaultCwd — so the
   * turn's tools run in the same directory the prompt's `[prompt:cwd]`
   * variable advertises. Passed to the orchestrator as an explicit `cwd`
   * override only when non-null; when `null` no override is sent and the
   * orchestrator falls back to the server default cwd (matching the
   * pre-heartbeat-workspace behavior for a workspace without a defaultCwd).
   * When omitted, `null` (no override) — the extension wires the real getter
   * (against `conversationStore.getWorkspace`); tests inject a fake.
   */
  readonly getWorkspaceCwd?: (workspaceId: string) => Promise<string | null>;
  /**
   * Whether the configured workspace currently has any ACTIVE agents —
   * conversations driving (or queued for) a turn. When `config.inactiveOnly`
   * is `true`, the heartbeat SKIPS a fire while this returns `true` (the
   * workspace is busy). The extension wires the real check against
   * `conversationStore.listConversations({ workspaceId, status: ["active",
   * "queued"] })` (the configured workspace's persisted statuses — the
   * orchestrator sets `"active"` on turn start, `"idle"` on settle); tests
   * inject a fake. When omitted, `false` (no active agents → never skip) so
   * the inactive-only feature degrades off cleanly — the heartbeat fires
   * unconditionally, matching the pre-inactive-only behavior.
   */
  readonly hasActiveAgents?: (workspaceId: string) => Promise<boolean>;
}

interface ActiveRun {
  readonly conversationId: string;
  readonly workspaceId: string;
  stopped: boolean;
}

export function createHeartbeatService(deps: HeartbeatServiceDeps): HeartbeatService {
  const logger = deps.logger;
  const timers = deps.timers ?? realTimers;
  const generateId = deps.generateId ?? (() => crypto.randomUUID());
  const configStore: HeartbeatConfigStore = createHeartbeatConfigStore(deps.storage);
  const runStore: HeartbeatRunStore = createHeartbeatRunStore(deps.storage);
  const orchestrator = deps.orchestrator;
  // Default: pass templates through UNRESOLVED (raw). The extension wires the
  // real resolver so [type:name] placeholders are substituted like the global
  // system-prompt template; tests inject a fake.
  const resolvePrompt = deps.resolvePrompt ?? ((template: string) => Promise.resolve(template));
  // Default: an empty systemPrompt stays empty (no system prompt). The
  // extension wires the real getter so empty INHERITS the global system
  // prompt template (GET /system-prompt); tests inject a fake.
  const getGlobalSystemPrompt = deps.getGlobalSystemPrompt ?? (() => Promise.resolve(""));
  // Default: no cwd override (the orchestrator resolves the turn cwd from the
  // conversation's workspace). The extension wires the real getter so the
  // turn pins to the CONFIGURED workspace's defaultCwd; tests inject a fake.
  const getWorkspaceCwd = deps.getWorkspaceCwd ?? (() => Promise.resolve(null));
  // Default: no active agents (never skip) — the inactive-only feature degrades
  // off cleanly. The extension wires the real check (against the conversation
  // store's persisted statuses); tests inject a fake.
  const hasActiveAgents = deps.hasActiveAgents ?? (() => Promise.resolve(false));

  // runId → active-run tracking (in-memory; the durable record lives in the
  // run store). Used to (a) map a stop request to its conversation, and
  // (b) keep a "stopped" flag so the turn's completion doesn't clobber a
  // user-initiated stop.
  const activeRuns = new Map<string, ActiveRun>();

  const scheduler = new HeartbeatScheduler({
    timers,
    fire: (workspaceId) => fire(workspaceId),
  });

  async function fire(workspaceId: string): Promise<void> {
    const config = await configStore.get(workspaceId);
    // Race: disabled/disarmed between the timer firing and now.
    if (!config.enabled) return;

    // inactiveOnly: skip this fire when the configured workspace has active
    // agents (a conversation driving or queued for a turn). The fire is
    // silently skipped — no run is recorded — and the scheduler re-arms to
    // try again at the next interval. The spawned heartbeat conversation lives
    // in the DEDICATED heartbeat workspace, so it never self-blocks (a prior
    // in-flight heartbeat run is NOT an active agent of the configured
    // workspace). Disabled (inactiveOnly === false) fires unconditionally.
    if (config.inactiveOnly && (await hasActiveAgents(workspaceId))) {
      logger?.info("heartbeat: fire skipped — workspace has active agents", { workspaceId });
      return;
    }

    const conversationId = generateId();
    const runId = generateId();
    const triggeredAt = new Date(timers.now()).toISOString();
    const run: HeartbeatRun = {
      id: runId,
      conversationId,
      triggeredAt,
      status: "running",
    };
    await runStore.create(workspaceId, run);
    activeRuns.set(runId, { conversationId, workspaceId, stopped: false });

    logger?.info("heartbeat: run started", { workspaceId, runId, conversationId });

    // Resolve the heartbeat's prompts ONCE, when the turn is constructed.
    //
    // CR-HB-2: an empty `systemPrompt` INHERITS the global system prompt
    // template (the same one `GET /system-prompt` returns / that regular
    // conversations resolve) — empty is an override-means-inherit flag, not
    // "no system prompt". A non-empty `systemPrompt` is an explicit override.
    // This step runs FIRST.
    //
    // CR-HB-1: then `[type:name]` variable placeholders in whichever prompt is
    // in effect are resolved via the same resolver + variable catalog the
    // global system-prompt template uses. The orchestrator sends an explicit
    // systemPrompt override AS-IS (bypassing its own templated prompt), so
    // resolution must happen HERE, before handleMessage. For prompts using
    // stable variables (os/cwd/git) this yields a stable, cache-warm prompt
    // across runs; time-bearing variables refresh per run (mirroring the
    // global template's per-conversation resolution).
    const baseSystemPrompt =
      config.systemPrompt === "" ? await getGlobalSystemPrompt() : config.systemPrompt;
    const resolveCtx = { workspaceId, conversationId, model: config.model };
    // resolveCtx uses the CONFIGURED workspaceId — the heartbeat operates
    // ON BEHALF OF the configured workspace, so `[prompt:workspace_id]` and
    // `[prompt:cwd]` refer to it (not the heartbeat workspace the spawned
    // conversation is filed in). The turn's cwd is pinned to the SAME
    // configured workspace's defaultCwd (below) so tools run where the
    // prompt's `[prompt:cwd]` advertises.
    const [systemPrompt, taskPrompt, configuredWorkspaceCwd] = await Promise.all([
      resolvePrompt(baseSystemPrompt, resolveCtx),
      resolvePrompt(config.taskPrompt, resolveCtx),
      getWorkspaceCwd(workspaceId),
    ]);

    try {
      await orchestrator.handleMessage({
        conversationId,
        text: taskPrompt,
        // Fire-and-forget: the heartbeat loop does not consume the
        // streamed events (it only awaits turn completion to mark the
        // run done). A no-op onEvent satisfies the required callback.
        onEvent: () => {},
        // Always passed explicitly — bypasses the orchestrator's templated
        // workspace prompt. Resolved above: an empty config systemPrompt
        // inherited the global template (CR-HB-2), then [type:name]
        // placeholders were substituted (CR-HB-1). Still "" when the global
        // template itself is empty (no system prompt).
        systemPrompt,
        ...(config.model !== "" ? { modelName: config.model } : {}),
        ...(config.reasoningEffort !== null ? { reasoningEffort: config.reasoningEffort } : {}),
        // Pin the turn cwd to the CONFIGURED workspace's defaultCwd so
        // the heartbeat's tools run in the same directory its prompt
        // variables advertise — NOT the heartbeat workspace's (empty)
        // defaultCwd → process.cwd(). Omitted when the configured
        // workspace has no defaultCwd (the orchestrator then falls back
        // to the server default cwd, matching the pre-heartbeat-
        // workspace behavior for a workspace without one).
        ...(configuredWorkspaceCwd !== null ? { cwd: configuredWorkspaceCwd } : {}),
        // File the spawned conversation in the DEDICATED heartbeat
        // workspace (not the configured workspace) so heartbeat
        // conversations don't clog the configured workspace's tabs. The
        // orchestrator auto-creates this workspace on first fire
        // (ensureWorkspace), so it appears on the workspaces home page.
        workspaceId: HEARTBEAT_WORKSPACE_ID,
      });
    } finally {
      const entry = activeRuns.get(runId);
      activeRuns.delete(runId);
      // If the user stopped it, stopRun already set "stopped"; don't
      // clobber. Otherwise the turn sealed (normally or via abort) → done.
      if (entry !== undefined && !entry.stopped) {
        await runStore.setStatus(workspaceId, runId, "completed");
        logger?.info("heartbeat: run completed", { workspaceId, runId });
      }
    }
  }

  return {
    async getConfig(workspaceId) {
      return configStore.get(workspaceId);
    },

    async updateConfig(workspaceId, update) {
      const next = await configStore.update(workspaceId, update);
      // Arm/disarm from the new config. An in-progress run is left alone;
      // the new interval takes effect on the next re-arm.
      scheduler.arm(workspaceId, next);
      logger?.info("heartbeat: config updated", {
        workspaceId,
        enabled: next.enabled,
        intervalMinutes: next.intervalMinutes,
      });
      return next;
    },

    async listRuns(workspaceId) {
      return runStore.list(workspaceId);
    },

    async nextRunAt(workspaceId) {
      const ms = scheduler.nextFireAt(workspaceId);
      return ms === null ? null : new Date(ms).toISOString();
    },

    async stopRun(workspaceId, runId) {
      const run = await runStore.get(workspaceId, runId);
      if (run === null) {
        throw new Error("Heartbeat run not found");
      }
      // Idempotent: an already-finished run is a no-op.
      if (run.status !== "running") {
        return { ok: true };
      }
      const entry = activeRuns.get(runId);
      const conversationId = entry?.conversationId ?? run.conversationId;
      if (entry !== undefined) {
        entry.stopped = true;
      }
      await runStore.setStatus(workspaceId, runId, "stopped");
      orchestrator.stopTurn(conversationId);
      logger?.info("heartbeat: run stopped", { workspaceId, runId, conversationId });
      return { ok: true };
    },

    async startAll() {
      // Sweep stale "running" runs (orphaned by a prior crash/restart) →
      // "stopped". Never leave the system showing an in-flight run that
      // can never finish.
      const workspaceIds = await configStore.listWorkspaceIds();
      for (const workspaceId of workspaceIds) {
        const runs = await runStore.list(workspaceId);
        for (const run of runs) {
          if (run.status === "running") {
            await runStore.setStatus(workspaceId, run.id, "stopped");
          }
        }
        const config = await configStore.get(workspaceId);
        if (config.enabled) {
          scheduler.arm(workspaceId, config);
          logger?.info("heartbeat: scheduler armed on boot", {
            workspaceId,
            intervalMinutes: config.intervalMinutes,
          });
        }
      }
    },

    stopAll() {
      scheduler.disarmAll();
    },
  };
}