package agents

import (
	"context"
	"errors"
	"log/slog"
	"strings"

	"g.fc.run/misc/byre/internal/api"
	"g.fc.run/misc/byre/internal/store"
)

const handoffPrompt = `Write a handoff for a fresh agent that will continue this task with none of your context. ` +
	`Cover: the goal; decisions made and why; the current state (what is done, what is in progress, what is verified); ` +
	`dead ends tried; open questions; and the files that matter. Be complete: the next agent sees nothing else. ` +
	`Your final message is the handoff, and nothing else.`

const handoffPreamble = "You are continuing this task from a previous agent session, which ended so the work could go on with a fresh context. Its handoff follows.\n\n"

const leadHandoffPreamble = "You are continuing as the human's lead agent from a previous session, which ended so you could go on with a fresh context. Its handoff follows. Signals that arrived meanwhile come next.\n\n"

const leadHandoffPrompt = `Write a handoff for a fresh lead agent that will take over from you with none of your context. ` +
	`Cover: the human's standing instructions and preferences; what each task you are tracking is doing and what you are waiting on from it; ` +
	`questions you have surfaced or answered and why; what you last pointed the human's attention at; and anything you promised to do or check. ` +
	`Be complete: the next agent sees nothing else. Your final message is the handoff, and nothing else.`

func (m *Manager) Compact(ctx context.Context, sessionID string) (api.AgentSession, error) {
	sess, err := m.store.GetSession(ctx, sessionID)
	if err != nil {
		return api.AgentSession{}, err
	}
	if sess.Owner != "" {
		return m.Send(ctx, sessionID, "byre", leadHandoffPrompt, "")
	}
	return m.Send(ctx, sessionID, "byre", handoffPrompt, "")
}

func isHandoffPrompt(actor, text string) bool {
	return actor == "byre" && (text == handoffPrompt || text == leadHandoffPrompt)
}

func isContinuation(actor, text string) bool {
	return actor == "byre" && (strings.HasPrefix(text, handoffPreamble) || strings.HasPrefix(text, leadHandoffPreamble))
}

func (m *Manager) continueFromHandoff(sessionID, handoff string) {
	ctx := context.Background()
	err := m.handoff(ctx, sessionID, handoff)
	if err != nil {
		slog.Error("continue from handoff", "session", sessionID, "err", err)
	}
}

func (m *Manager) handoff(ctx context.Context, sessionID, handoff string) error {
	sess, err := m.store.GetSession(ctx, sessionID)
	if err != nil {
		return err
	}
	creator, err := m.store.GetUser(ctx, sess.CreatedBy)
	if err != nil {
		return err
	}

	if sess.Owner != "" {
		err = m.retire(ctx, sess, "byre")
		if err != nil {
			return err
		}
		_, err = m.createLead(ctx, creator, leadHandoffPreamble+handoff, sess.Model, "byre", nil)
		return err
	}

	discard, err := m.store.GetDiscard(ctx, sess.TaskId)
	if err != nil {
		return err
	}
	if discard.State != store.DiscardNone {
		m.startDiscard(sess.TaskId)
		return nil
	}
	err = transition(ctx, m.store, sess.Id, api.AgentSessionStateIdle, api.AgentSessionStateCompleted, "byre")
	if err != nil {
		return err
	}
	m.stopLive(sess.Id)

	task, err := m.store.GetTask(ctx, sess.TaskId)
	if err != nil {
		return err
	}
	_, err = m.create(ctx, task, creator, handoffPreamble+handoff, sess.Model, "byre", nil)
	if errors.Is(err, ErrConflict) {
		m.startDiscard(task.Id)
		return nil
	}
	return err
}