/**
 * goal-driven-loop extension for Pi.
 *
 * Wires together trigger detection, state injection, and timed
 * auto-defaults to eliminate unnecessary user interaction.
 */

import type { ExtensionAPI, ExtensionContext } from "@earendil-works/pi-coding-agent";
import { join } from "node:path";
import { existsSync, unlinkSync } from "node:fs";
import { detectTrigger, isCoarseGrained } from "./trigger-detector.js";
import {
  readGoalState,
  buildInjectionText,
  buildContinuationPrompt,
  type GoalState,
} from "./state-injector.js";
import {
  promptStaleState,
  notifyCoarseGrainedDelegation,
  notifyMidLoopUpgrade,
  notifyStagnation,
  shouldNotifyStagnation,
  type UIContext,
} from "./ui-prompts.js";

const CONTEXT_TENSION_THRESHOLD = 0.8;
const STAGNATION_KEYWORDS = [
  "found",
  "fixed",
  "implemented",
  "added",
  "refactored",
  "verified",
];
const ABANDON_KEYWORDS = ["abandon", "cancel", "不要了", "放弃", "停"];

function buildUIContext(ctx: ExtensionContext): UIContext {
  return {
    hasUI: ctx.hasUI,
    select: ctx.ui.select.bind(ctx.ui),
    notify: ctx.ui.notify.bind(ctx.ui),
    confirm: ctx.ui.confirm.bind(ctx.ui),
  };
}

function handleAbandon(ctx: ExtensionContext): void {
  const goalPath = join(ctx.cwd, ".agents", "goal", "GOAL.md");
  try {
    if (existsSync(goalPath)) {
      unlinkSync(goalPath);
    }
  } catch {
    // best effort
  }
  if (ctx.hasUI) {
    ctx.ui.notify("目标已放弃", "info");
  }
}

/**
 * Check if the progress log shows stagnation (dual signal).
 * Stagnation = criteria passing count unchanged for 3 iterations
 * AND no progress keywords in the last 3 iterations.
 */
function detectStagnation(state: GoalState): boolean {
  // Signal 1: We can't compare passing counts across iterations
  // from the file alone without history. Instead, check if the
  // last 3 iteration headers exist but have no progress keywords.
  // For a more robust check, the skill should track passing count
  // history in GOAL.md. For now, we rely on the skill's own
  // stagnation detection and the extension's stagnation counter.
  return false; // Placeholder — skill-side detection is authoritative
}

export default function (pi: ExtensionAPI) {
  let consecutiveStagnations = 0;

  // ---- Trigger detection on user input ----
  pi.on("input", async (event, ctx) => {
    if (event.source === "extension") {
      return { action: "continue" };
    }

    // Check for explicit abandon first
    const lowerText = event.text.toLowerCase();
    const isAbandon = ABANDON_KEYWORDS.some((kw) =>
      lowerText.includes(kw.toLowerCase())
    );
    if (isAbandon) {
      const state = readGoalState(ctx.cwd);
      if (state) {
        handleAbandon(ctx);
        return { action: "continue" };
      }
    }

    // Try to detect a goal-setting trigger
    const match = detectTrigger(event.text);
    if (!match) {
      return { action: "continue" };
    }

    // Trigger detected — check stale state
    const existingState = readGoalState(ctx.cwd);
    if (existingState && existingState.status === "in-progress") {
      const ui = buildUIContext(ctx);
      const choice = await promptStaleState(ui);
      if (choice === "abandon") {
        handleAbandon(ctx);
        return { action: "continue" };
      }
      if (choice === "replace") {
        // Let the skill handle replacement on the next turn
        return { action: "continue" };
      }
      // "continue" or undefined → let the skill resume
    }

    // Granularity check
    if (isCoarseGrained(match.goalText)) {
      const ui = buildUIContext(ctx);
      notifyCoarseGrainedDelegation(ui, match.goalText);
      // Check if comet is available (has openspec directory)
      const hasOpenspec = existsSync(join(ctx.cwd, "openspec"));
      if (hasOpenspec) {
        pi.sendUserMessage(`/skill:comet-open ${match.goalText}`, {
          deliverAs: "followUp",
        });
      } else {
        // Fallback: inject multi-stage mode instruction
        pi.sendMessage(
          {
            customType: "goal-driven-loop-coarse-fallback",
            content: `Coarse-grained goal detected but comet unavailable. Running in multi-stage mode. Split the goal into phases and verify each one:\n\n${match.goalText}`,
            display: true,
          },
          { triggerTurn: true, deliverAs: "followUp" }
        );
      }
      return { action: "continue" };
    }

    // Fine-grained — let the skill handle it
    return { action: "continue" };
  });

  // ---- State injection on every agent start ----
  pi.on("before_agent_start", async (event, ctx) => {
    const state = readGoalState(ctx.cwd);
    if (!state) {
      return;
    }

    // Context tension check
    const usage = ctx.getContextUsage();
    if (
      usage &&
      usage.contextWindow > 0 &&
      usage.tokens / usage.contextWindow > CONTEXT_TENSION_THRESHOLD
    ) {
      const continuationMsg = buildContinuationPrompt(state);
      return {
        systemPrompt:
          event.systemPrompt +
          "\n\n" +
          continuationMsg +
          "\n\nContext is tight. Finalize .agents/goal/GOAL.md updates before completing this turn.",
      };
    }

    // Stagnation auto-recovery injection
    if (state.status === "blocked") {
      consecutiveStagnations++;
      if (shouldNotifyStagnation(consecutiveStagnations)) {
        const ui = buildUIContext(ctx);
        notifyStagnation(
          ui,
          state.goal,
          state.passedCriteria,
          state.totalCriteria,
          state.iteration
        );
      } else {
        // Auto-inject strategy-change prompt
        return {
          systemPrompt:
            event.systemPrompt +
            "\n\n" +
            buildInjectionText(state) +
            "\n\n[goal-driven-loop STAGNATION RECOVERY] Previous approach not making progress. Try: a different tool/library, refactor before retry, or split the failing criterion into sub-steps.",
        };
      }
    }

    // Normal goal state injection
    if (state.status !== "blocked") {
      consecutiveStagnations = 0;
    }

    const injection = buildInjectionText(state);
    return {
      systemPrompt: event.systemPrompt + "\n\n" + injection,
    };
  });
}