import type { FastifyBaseLogger } from 'fastify';
import type { Sql } from '../../db.js';
import type { Config } from '../../config.js';
import type {
  Agent,
  ErrorReason,
  Message,
  MessageMetadata,
  Project,
  Session,
  ToolCall,
  UserStreamFrame,
} from '../../types/api.js';
import { ALL_TOOLS } from '../tools.js';
import { resolveProjectRoot } from '../path_guard.js';
import { maybeAutoNameChat } from '../auto_name.js';
import { getAgentById } from '../agents.js';
import * as compaction from '../compaction.js';
import type { Broker } from '../broker.js';
import { resolveToolBudget } from './budget.js';
import {
  detectDoomLoop,
} from './sentinels.js';
import {
  buildMessagesPayload,
  loadContext,
} from './payload.js';
import {
  finalizeCompletion,
  handleAbortOrError,
} from './error-handler.js';
import {
  executeStreamPhase,
} from './stream-phase.js';
import { executeToolPhase, type ToolPhaseResult } from './tool-phase.js';
import type { StreamPhaseState } from './types.js';
import {
  runCapHitSummary,
  runDoomLoopSummary,
  runStepCapSummary,
} from './sentinel-summaries.js';

// v1.14.0: hard ceiling on the number of stream-and-tool iterations per
// user-message turn. Per-agent cap via agent.steps is the primary knob;
// MAX_STEPS is the safety ceiling. 200 is 4x the effective budget ceiling
// (50 tool calls) — in practice budget fires first unless the model makes
// many 0-tool-call iterations (which exit the loop via the non-tool finish
// path anyway).
export const MAX_STEPS = 200;

// v1.12.4: re-exported so external callers (tests, future consumers) keep
// importing from services/inference.js as the public surface.
export { detectDoomLoop, DOOM_LOOP_THRESHOLD } from './sentinels.js';
export { buildMessagesPayload } from './payload.js';

export interface InferenceFrame {
  type:
    | 'message_started'
    | 'delta'
    | 'tool_call'
    | 'tool_result'
    | 'message_complete'
    | 'usage'
    | 'messages_deleted'
    | 'session_renamed'
    | 'chat_renamed'
    | 'error';
  message_id?: string;
  message_ids?: string[];
  chat_id?: string;
  tool_message_id?: string;
  tool_call_id?: string;
  // v1.8.2: 'system' added so cap-hit sentinel messages can announce themselves
  // through the normal message_started → delta → message_complete sequence.
  role?: 'assistant' | 'tool' | 'user' | 'system';
  content?: string;
  tool_call?: ToolCall;
  output?: unknown;
  truncated?: boolean;
  error?: string;
  // v1.8.2: structured error reason. Set on `type: 'error'` so the UI can
  // surface a specific message; `error` stays the human-readable text.
  reason?: ErrorReason;
  // v1.8.2: piggybacks on `message_complete` so static or terminally-resolved
  // messages can carry their persisted metadata to the live stream without a
  // refetch (sentinels carry { kind: 'cap_hit', ... }; failed messages carry
  // { kind: 'error', ... }).
  metadata?: MessageMetadata | null;
  tokens_used?: number | null;
  ctx_used?: number | null;
  ctx_max?: number | null;
  completion_tokens?: number | null;
  started_at?: string | null;
  finished_at?: string | null;
  model?: string;
  session_id?: string;
  name?: string;
}

export type FramePublisher = (sessionId: string, frame: InferenceFrame) => void;

export interface InferenceContext {
  sql: Sql;
  config: Config;
  log: FastifyBaseLogger;
  publish: FramePublisher;
  publishUser: (frame: UserStreamFrame) => void;
  // v1.11: passed through so compaction.process can publish 'compacted'
  // frames on the same session WS channel useSessionStream subscribes to.
  // Compaction is the only path that needs the raw broker handle (regular
  // inference goes through `publish`); keeping a separate field avoids
  // tempting other code paths into bypassing the session-id binding.
  broker: Broker;
}

// v1.12.4: payload assembly extracted to ./inference/payload.ts (tests
// import buildMessagesPayload from this module, so a re-export below
// preserves the public surface). Stream + tool phases extracted to
// ./inference/stream-phase.ts and ./inference/tool-phase.ts.

export interface StreamResult {
  finishReason: string | null;
  content: string;
  toolCalls: ToolCall[];
  promptTokens: number | null;
  completionTokens: number | null;
  // v1.13.1-C: reasoning text accumulated across reasoning-delta parts.
  // Empty string when the model doesn't emit reasoning (most cases).
  reasoning: string;
}


export interface TurnArgs {
  sessionId: string;
  chatId: string;
  assistantMessageId: string;
  // v1.8.2: cumulative tool calls executed this run. Compared against the
  // resolved budget at the top of each turn. Replaces the older `depth`
  // counter (which counted iterations, not invocations).
  toolsUsed: number;
  // v1.11.6: ordered tool calls executed in this user-message turn (across
  // recursive runAssistantTurn invocations). Reset to [] at user-message
  // boundaries by runInference, same as toolsUsed. Doom-loop check at the
  // top of runAssistantTurn slices the last DOOM_LOOP_THRESHOLD entries.
  recentToolCalls: ToolCall[];
  signal: AbortSignal | undefined;
}


export async function runAssistantTurn(
  ctx: InferenceContext,
  args: TurnArgs,
): Promise<void> {
  const { sessionId, chatId, signal } = args;

  // v1.14.0: resolve agent once at the top. The agent stays fixed for the
  // duration of this user-message turn — PATCH agent_id mid-conversation
  // takes effect on the next runInference, not mid-loop.
  const initialLoaded = await loadContext(ctx.sql, sessionId, chatId);
  if (!initialLoaded) {
    ctx.log.warn({ sessionId }, 'inference: session or project missing');
    return;
  }
  const { session, project } = initialLoaded;
  const agent = session.agent_id
    ? await getAgentById(project.path, session.agent_id)
    : null;
  const budget = resolveToolBudget(agent);

  // v1.14.0: effectiveCap = min(agent.steps ?? Infinity, MAX_STEPS).
  // steps: 0 means "no tool calls allowed" — the first stream phase runs
  // but if it emits tool calls they are not executed (finalize as text-only).
  const effectiveCap = Math.min(agent?.steps ?? Infinity, MAX_STEPS);

  // steps: 0 special case — model responds text-only. The while loop would
  // never enter (effectiveCap === 0), so we handle it explicitly before the
  // loop. The model always gets at least one chance to respond with text.
  if (effectiveCap === 0) {
    const loaded = await loadContext(ctx.sql, sessionId, chatId);
    if (loaded) {
      await runTextOnlyTurn(ctx, args, loaded.session, loaded.project, loaded.history, agent);
    }
    return;
  }

  let stepNumber = 0;
  let toolsUsed = args.toolsUsed;
  let recentToolCalls = args.recentToolCalls;
  let assistantMessageId = args.assistantMessageId;

  while (stepNumber < effectiveCap) {
    // ---- doom-loop check (moved from top-of-function) ----
    const loop = detectDoomLoop(recentToolCalls);
    if (loop) {
      // Need fresh history for the summary.
      const loaded = await loadContext(ctx.sql, sessionId, chatId);
      if (loaded) {
        const iterArgs: TurnArgs = { sessionId, chatId, assistantMessageId, toolsUsed, recentToolCalls, signal };
        await runDoomLoopSummary(ctx, iterArgs, loaded.session, loaded.project, loaded.history, agent, loop);
      }
      break;
    }

    // ---- budget check (moved from top-of-function) ----
    if (toolsUsed >= budget) {
      const loaded = await loadContext(ctx.sql, sessionId, chatId);
      if (loaded) {
        const iterArgs: TurnArgs = { sessionId, chatId, assistantMessageId, toolsUsed, recentToolCalls, signal };
        await runCapHitSummary(ctx, iterArgs, loaded.session, loaded.project, loaded.history, agent, budget);
      }
      break;
    }

    // ---- compaction check ----
    // v1.11: if the prior turn flagged this chat for compaction, run it
    // before loadContext so we read post-compaction history. Swallow
    // failures and proceed with un-compacted history.
    const chatFlag = await ctx.sql<{ needs_compaction: boolean }[]>`
      SELECT needs_compaction FROM chats WHERE id = ${chatId}
    `;
    if (chatFlag[0]?.needs_compaction) {
      try {
        await compaction.process({
          sql: ctx.sql,
          config: ctx.config,
          log: ctx.log,
          broker: ctx.broker,
          chatId,
        });
      } catch (err) {
        ctx.log.warn({ err, chatId }, 'auto-compaction failed; clearing flag and proceeding');
        await ctx.sql`UPDATE chats SET needs_compaction = false WHERE id = ${chatId}`;
      }
    }

    // ---- load context (must re-load each iteration — new messages since last step) ----
    const loaded = await loadContext(ctx.sql, sessionId, chatId);
    if (!loaded) {
      ctx.log.warn({ sessionId }, 'inference: session or project missing mid-loop');
      break;
    }
    const { session: iterSession, project: iterProject, history } = loaded;
    const projectRoot = await resolveProjectRoot(iterProject.path);

    // v1.14.0: log step boundary for instrumentation. step_start parts are in
    // the schema CHECK but not emitted here — writing to the assistant message
    // before the stream phase creates a sequence-0 collision with
    // partsFromAssistantMessage. A WS frame or structured log is sufficient
    // since the frontend doesn't render step boundaries in v1.14.
    ctx.log.info({ sessionId, chatId, step: stepNumber, assistantMessageId }, 'step_start');

    // ---- build messages + stream phase ----
    const messages = await buildMessagesPayload(iterSession, iterProject, history, agent, ctx.log);
    const webToolsEnabled =
      iterSession.web_search_enabled ?? iterProject.default_web_search_enabled ?? false;

    const iterArgs: TurnArgs = { sessionId, chatId, assistantMessageId, toolsUsed, recentToolCalls, signal };
    const state: StreamPhaseState = { accumulated: '', startedAt: null };
    let result: StreamResult;
    try {
      result = await executeStreamPhase(ctx, iterArgs, iterSession, messages, state, agent, webToolsEnabled);
    } catch (err) {
      await handleAbortOrError(ctx, iterArgs, state.accumulated, err);
      break;
    }

    // ---- non-tool finish → finalize and exit ----
    if (result.toolCalls.length === 0) {
      await finalizeCompletion(ctx, iterArgs, result, state.startedAt, iterSession);
      break;
    }

    // ---- steps: 0 edge case ----
    // effectiveCap check above guarantees we're inside the loop, but this
    // guard handles the theoretical case where the model emits tool calls
    // on step 0 when effectiveCap would have been 0 (impossible since the
    // while condition prevents entry, but kept for safety). If effectiveCap
    // is 1 and we're on step 0, tool calls ARE executed — steps counts
    // iterations, not post-first-stream.

    // ---- tool phase ----
    let toolPhaseResult: ToolPhaseResult;
    try {
      toolPhaseResult = await executeToolPhase(ctx, iterArgs, result, state.startedAt, iterSession, projectRoot);
    } catch (err) {
      // Tool phase errors are unexpected (individual tool failures are
      // caught inside executeToolPhase). Log and break.
      ctx.log.error({ err, sessionId, chatId, step: stepNumber }, 'tool phase threw unexpectedly');
      break;
    }

    // ---- update loop locals ----
    toolsUsed += toolPhaseResult.toolCallCount;
    recentToolCalls = [...recentToolCalls, ...toolPhaseResult.toolCalls];
    stepNumber++;

    if (toolPhaseResult.action !== 'continue') {
      // 'paused' (user input) or 'synthesis_done' — stop the loop.
      break;
    }
    // 'continue' — advance to next assistant message.
    assistantMessageId = toolPhaseResult.nextAssistantId!;
  }

  // ---- post-loop: step-cap sentinel ----
  // When the loop exits because stepNumber reached effectiveCap, the last
  // iteration's tool phase returned 'continue' with a nextAssistantId that
  // is still in 'streaming' status (unfilled). Use it for the wrap-up.
  if (stepNumber >= effectiveCap && effectiveCap < Infinity) {
    const loaded = await loadContext(ctx.sql, sessionId, chatId);
    if (loaded) {
      const capArgs: TurnArgs = { sessionId, chatId, assistantMessageId, toolsUsed, recentToolCalls, signal };
      await runStepCapSummary(ctx, capArgs, loaded.session, loaded.project, loaded.history, agent, stepNumber, effectiveCap);
    }
  }
}

// v1.14.0: special handling for steps: 0 — the model responds text-only.
// The while loop never enters (effectiveCap === 0). We stream once with
// no tools, finalize, and return. If the model emits tool calls despite
// not being offered tools, they're ignored (finalize as text-only).
async function runTextOnlyTurn(
  ctx: InferenceContext,
  args: TurnArgs,
  session: Session,
  project: Project,
  history: Message[],
  agent: Agent | null,
): Promise<void> {
  const messages = await buildMessagesPayload(session, project, history, agent, ctx.log);
  // Web tools are irrelevant when steps: 0 (no tool execution), but we
  // still need to resolve the flag for executeStreamPhase's signature.
  const webToolsEnabled =
    session.web_search_enabled ?? project.default_web_search_enabled ?? false;

  const state: StreamPhaseState = { accumulated: '', startedAt: null };
  let result: StreamResult;
  try {
    result = await executeStreamPhase(ctx, args, session, messages, state, agent, webToolsEnabled);
  } catch (err) {
    await handleAbortOrError(ctx, args, state.accumulated, err);
    return;
  }

  if (result.toolCalls.length > 0) {
    ctx.log.warn(
      { chatId: args.chatId, toolCallCount: result.toolCalls.length },
      'steps: 0 agent emitted tool calls; ignoring and finalizing as text-only',
    );
    // Override: strip tool calls so finalizeCompletion treats it as text-only.
    result = { ...result, toolCalls: [] };
  }

  await finalizeCompletion(ctx, args, result, state.startedAt, session);
}

export async function runInference(
  ctx: InferenceContext,
  sessionId: string,
  chatId: string,
  assistantMessageId: string,
  signal?: AbortSignal
): Promise<void> {
  // v1.8.2: every fresh inference (initial send, regenerate, force_send,
  // continue) starts with a clean budget. Tool-call accumulation across
  // Continue invocations is what the hard ceiling guards against, not the
  // per-call budget.
  // v1.11.6: recentToolCalls also resets — doom-loop detection is scoped
  // to a single user-message turn, so a Continue starts with no history.
  return runAssistantTurn(ctx, {
    sessionId,
    chatId,
    assistantMessageId,
    toolsUsed: 0,
    recentToolCalls: [],
    signal,
  });
}

// v1.8.2: cap-hit summary flow. Called instead of erroring when the loop
// hits its budget. Reuses the in-flight assistant message slot to stream a
// short wrap-up reply with the synthetic note prepended and tools disabled,
// then always inserts a cap_hit sentinel afterward (regardless of summary
// outcome) so the UI can show a Continue affordance.
interface InferenceRegistration {
  controller: AbortController;
  completed: Promise<void>;
}

export function createInferenceRunner(
  ctx: Omit<InferenceContext, 'publishUser'>,
  publishUserFn: (user: string, frame: UserStreamFrame) => void
) {
  const registry = new Map<string, InferenceRegistration>();

  return {
    enqueue(sessionId: string, chatId: string, assistantMessageId: string, user: string) {
      const callCtx: InferenceContext = {
        ...ctx,
        publishUser: (frame) => publishUserFn(user, frame),
        // v1.11: broker comes in via ctx (set at registration time). Repeated
        // here so the destructure carries it onto the per-call ctx without
        // having to add it to every enqueue/cancel signature individually.
        broker: ctx.broker,
      };
      // v1.8 mobile-tabs: announce working before the async loop starts so
      // every device subscribed to the user channel sees the amber dot.
      callCtx.publishUser({ type: 'chat_status', chat_id: chatId, status: 'streaming', at: new Date().toISOString() });
      const controller = new AbortController();
      let resolveCompleted!: () => void;
      const completed = new Promise<void>((res) => { resolveCompleted = res; });
      const registration: InferenceRegistration = { controller, completed };
      registry.set(chatId, registration);
      void (async () => {
        try {
          await runInference(callCtx, sessionId, chatId, assistantMessageId, controller.signal);
          setImmediate(() => {
            void maybeAutoNameChat(callCtx, chatId, sessionId).catch((err: Error) => {
              callCtx.log.warn({ err, chatId }, 'auto-name failed');
            });
          });
        } catch (err) {
          callCtx.log.error({ err }, 'unhandled inference error');
        } finally {
          resolveCompleted();
          // Only clear our own registration; a force-send may have replaced it.
          if (registry.get(chatId) === registration) {
            registry.delete(chatId);
          }
        }
      })();
    },

    async cancel(_sessionId: string, chatId: string): Promise<boolean> {
      const reg = registry.get(chatId);
      if (!reg) return false;
      reg.controller.abort();
      // Swallow — we just need to wait for the catch/finally to persist state.
      await reg.completed.catch(() => {});
      return true;
    },

    hasActive(chatId: string): boolean {
      return registry.has(chatId);
    },
  };
}

export const _toolNames = ALL_TOOLS.map((t) => t.name);