package loop

import (
	"context"
	"fmt"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/agent"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/capacity"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/model"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/trace"
)

// Run drives the agent loop: assemble a fresh model-visible context every round
// (re-inject relevant memory from the current conversation, optionally compacting
// the older turns when the context exceeds the configured budget), then run up to
// MaxRounds steps. Each step runs the model (streaming through OnStream when
// configured) and any requested tool calls are executed under a per-invoke
// timeout and fed back as RoleTool messages so the model can continue.
// A checkpoint is persisted at every step, every step is traced as a
// state_transition span (with an llm_call child and tool_call spans for each
// invocation), and after each step the memory Extractor runs with errors logged
// rather than fatal.
//
// When a turn settles with a Result, the OnTurnEnd hook is called once for that
// turn (never per step) and its mood label is recorded on Result.Mood, so the
// layers around the loop can advance persona state and tag the persisted reply.
//
// It returns the final answer, or a partial Result with StopReasonMaxRounds when
// the budget is exhausted without a final answer. Step errors are wrapped with %w
// so callers can classify them with errors.Is.
func (l *Loop) Run(ctx context.Context, sessionID string, messages []model.Message) (*Result, error) {
	if ctx == nil {
		ctx = context.Background()
	}
	if l.agent == nil {
		return nil, fmt.Errorf("loop: run: %w", ErrNilAgent)
	}

	// Seed the per-Run capacity accumulator at quiet so the state can progress
	// (quiet→awake→full) across a multi-step tool loop; a nil/disabled decider
	// leaves it unused. It is scoped to this Run, so concurrent runs never share.
	// The session id rides the same context so a capacity_awaken emission can be
	// targeted to the session that produced it (design/14 §5).
	ctx = withCapState(ctx, &capStateAccum{state: capacity.StateQuiet})
	ctx = withLoopSession(ctx, sessionID)

	// Resume an interrupted run (design §1 durable execution): when the session
	// has a resumable checkpoint, rebuild its context and continue at the next
	// step rather than restarting from a fresh conversation. A different
	// sessionID — or a checkpoint left by a completed run — falls through to a
	// fresh start (LoadLatest misses, or the stop reason is not resumable).
	msgs, startStep, _ := l.loadCheckpoint(ctx, sessionID, messages)
	msgs = l.resolveImages(ctx, msgs)
	toolState := &toolLoopState{prevFP: make(map[string]bool)}
	res := &Result{}
	if l.flow != nil {
		l.flow.StartRound(sessionID, lastUserText(msgs))
		defer func() { l.flow.EndRound(sessionID, res.Text) }()
	}
	for step := startStep; step <= l.maxRounds; step++ {
		if err := ctx.Err(); err != nil {
			return nil, fmt.Errorf("loop: run: step %d: %w", step, err)
		}

		// Compact older turns when the conversation exceeds the context budget,
		// then assemble the model-visible context for this round (fresh memory
		// injection + transform hook), so every step sees an up-to-date context.
		msgs = l.compactIfNeeded(ctx, msgs)
		view := l.assembleContext(ctx, msgs, step)

		rc, roundSpan := l.span(ctx, "loop.step", trace.SpanKindStateTransition)
		outcome, err := l.step(rc, sessionID, view)
		if err != nil {
			l.spanProp(roundSpan, "error", err.Error())
			l.finishSpan(roundSpan, trace.SpanStatusError)
			return nil, fmt.Errorf("loop: run: step %d: %w", step, err)
		}
		l.spanProp(roundSpan, "step", step)
		l.spanProp(roundSpan, "stop_reason", outcome.stopReason)
		l.finishSpan(roundSpan, trace.SpanStatusOK)

		res.Steps = step
		if outcome.final {
			res.Text = outcome.text
			res.StopReason = outcome.stopReason
			l.saveCheckpoint(ctx, sessionID, step, msgs, outcome.stopReason)
			l.extractMemory(ctx, msgs, step)
			l.settleTurn(ctx, sessionID, msgs, res)
			return res, nil
		}

		batch, err := l.runToolCalls(rc, msgs, outcome.toolCalls, toolState)
		if err != nil {
			return nil, fmt.Errorf("loop: run: step %d: tools: %w", step, err)
		}
		msgs = batch.messages
		res.ToolCallsExecuted += batch.executed
		l.saveCheckpoint(ctx, sessionID, step, msgs, agent.StopReasonToolCalls)
		l.extractMemory(ctx, msgs, step)

		// The critical-tool-loop safety net (or a terminating hook) stops the
		// round without waiting for a real final answer.
		if batch.terminate {
			res.Text = criticalToolLoopTerminalReason
			res.StopReason = StopReasonToolLoopTerminated
			l.saveCheckpoint(ctx, sessionID, step, msgs, StopReasonToolLoopTerminated)
			l.extractMemory(ctx, msgs, step)
			l.settleTurn(ctx, sessionID, msgs, res)
			return res, nil
		}
	}

	// Budget exhausted without a final answer.
	res.Steps = l.maxRounds
	res.StopReason = StopReasonMaxRounds
	l.saveCheckpoint(ctx, sessionID, l.maxRounds, msgs, StopReasonMaxRounds)
	l.extractMemory(ctx, msgs, l.maxRounds)
	l.settleTurn(ctx, sessionID, msgs, res)
	return res, nil
}