// P5 (SPLIT SKETCH): stream-phase.ts is now the BooCode I/O layer for the
// stream phase — `executeStreamPhase` owns the row UPDATE, message_started
// frame, debounced content flush, throttled usage publish, model-context
// lookup, and tool-whitelist filter. The generic AI-SDK adapter
// (streamCompletion / toModelMessages / buildAiTools / sampler helpers) moved
// to ./stream-phase-adapter.ts, which has no SQL/broker/publish deps and is
// unit-testable on its own. The adapter's public names are re-exported below so
// existing importers of './stream-phase.js' (sentinel-summaries, synthesis
// pipeline, the helper tests) keep working unchanged.

import type { Agent, Session } from '../../types/api.js';
import * as modelContext from '../model-context.js';
import { toolJsonSchemas, type ToolJsonSchema } from '../tools.js';
import { matchToolGlob } from '../agents.js';
import type { OpenAiMessage } from './payload.js';
import { createContentFlusher } from './content-flusher.js';
import type {
  StreamPhaseState,
  InferenceContext,
  StreamResult,
  TurnArgs,
} from './types.js';
import { streamCompletion, samplerOptsFromAgent } from './stream-phase-adapter.js';

export {
  streamCompletion,
  samplerOptsFromAgent,
  type StreamOptions,
  type SamplerOpts,
  type StreamAdapterContext,
} from './stream-phase-adapter.js';

export async function executeStreamPhase(
  ctx: InferenceContext,
  args: TurnArgs,
  session: Session,
  messages: OpenAiMessage[],
  state: StreamPhaseState,
  agent: Agent | null,
  // v1.11.8: when false, web_search and web_fetch are stripped from the
  // tool list sent to the LLM, so the model can't even attempt them.
  webToolsEnabled: boolean,
): Promise<StreamResult> {
  const { sessionId, chatId, assistantMessageId, signal } = args;

  const startedRow = await ctx.sql<{ started_at: string }[]>`
    UPDATE messages
    SET started_at = clock_timestamp()
    WHERE id = ${assistantMessageId}
    RETURNING started_at
  `;
  state.startedAt = startedRow[0]?.started_at ?? null;

  ctx.publish(sessionId, {
    type: 'message_started',
    message_id: assistantMessageId,
    chat_id: chatId,
    role: 'assistant',
  });

  const flusher = createContentFlusher(ctx.sql, assistantMessageId, () => state.accumulated);

  // Tool whitelist: if an agent is set, filter the global tool list to only the
  // tool names it allows. v1.15.0-mcp-multi: uses matchToolGlob for glob
  // pattern support (e.g. `context7_*`, `!web_*`). When no agent: send all tools.
  // v1.11.8: a second filter strips web_search + web_fetch unless the chat
  // has them explicitly enabled. Counts as an opt-in security boundary: the
  // model can't summon a tool that wasn't offered to it.
  const WEB_TOOL_NAMES: ReadonlySet<string> = new Set(['web_search', 'web_fetch']);
  const effectiveTools: ToolJsonSchema[] = (agent
    ? toolJsonSchemas().filter((t) => matchToolGlob(t.function.name, agent.tools))
    : toolJsonSchemas()
  ).filter((t) => webToolsEnabled || !WEB_TOOL_NAMES.has(t.function.name));

  // v1.12.2: ctx_max lookup is cached after the first hit per model, so this
  // is a Map probe in steady state. We capture nCtx once at the top of the
  // stream so the throttled usage publish doesn't refetch each tick.
  const mctxForStream = await modelContext.getModelContext(session.model);
  const nCtxForStream = mctxForStream?.n_ctx ?? null;

  // v1.12.2 → v1.13.1-A: live usage publishes were throttled to ~500ms when
  // the manual SSE parser saw `parsed.usage` per chunk. AI SDK v6 surfaces
  // usage only at stream end (result.usage promise), so the throttle is
  // effectively a single trailing publish. ChatThroughput will tick once at
  // stream completion rather than mid-stream — known regression vs v1.12.2,
  // recovered if a future dispatch interpolates from delta cadence.
  const USAGE_THROTTLE_MS = 500;
  let lastUsageAt = 0;
  let pendingUsage: { p: number | null; c: number | null } | null = null;
  let usageTimer: NodeJS.Timeout | null = null;
  const flushUsage = () => {
    if (!pendingUsage) return;
    const { p, c } = pendingUsage;
    pendingUsage = null;
    lastUsageAt = Date.now();
    ctx.publish(sessionId, {
      type: 'usage',
      message_id: assistantMessageId,
      chat_id: chatId,
      completion_tokens: c,
      ctx_used: p,
      ctx_max: nCtxForStream,
    });
  };

  try {
    return await streamCompletion(
      ctx,
      session.model,
      messages,
      {
        tools: effectiveTools,
        ...samplerOptsFromAgent(agent),
      },
      (delta) => {
        state.accumulated += delta;
        ctx.publish(sessionId, {
          type: 'delta',
          message_id: assistantMessageId,
          chat_id: chatId,
          content: delta,
        });
        ctx.log.debug({ sessionId, delta }, 'inference delta');
        flusher.scheduleFlush();
      },
      (prompt, completion) => {
        pendingUsage = { p: prompt, c: completion };
        const elapsed = Date.now() - lastUsageAt;
        if (elapsed >= USAGE_THROTTLE_MS) {
          flushUsage();
        } else if (!usageTimer) {
          usageTimer = setTimeout(() => {
            usageTimer = null;
            flushUsage();
          }, USAGE_THROTTLE_MS - elapsed);
        }
      },
      signal,
      agent,
    );
  } finally {
    if (usageTimer) {
      clearTimeout(usageTimer);
      usageTimer = null;
    }
    await flusher.drain();
  }
}