package loop

import (
	"context"
	"fmt"

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

// streamStep drives a streaming model call. It is the streaming counterpart of
// agent.RunStep: it builds the request from the agent's public surface, runs the
// loop's input guardrail, streams deltas through OnStream, runs the output
// guardrail and decodes any tool calls. Because RunStep does not expose a stream
// path, this method is owned by the loop; it mirrors the agent's semantics so the
// two behave identically apart from the delta callback.
func (l *Loop) streamStep(ctx context.Context, messages []model.Message) (*stepOutcome, error) {
	adapter := l.agent.Adapter()
	if adapter == nil {
		return nil, fmt.Errorf("loop: stream step: %w", ErrNoAdapter)
	}
	req := l.buildRequest(ctx, messages)

	if l.guards != nil {
		verdict, err := l.guards.CheckInput(ctx, &req)
		if err != nil {
			return nil, fmt.Errorf("loop: check input: %w", err)
		}
		if verdict != nil && !verdict.Allow {
			return &stepOutcome{final: true, text: verdict.Reason, stopReason: agent.StopReasonGuardrailInput}, nil
		}
	}

	resp, err := adapter.ChatStream(ctx, req, func(ev model.StreamEvent) {
		// Stamp the session/turn identity at the loop boundary: the adapter runs
		// below the loop and cannot know which conversation the stream belongs to,
		// so the loop fills it from the context it was driven with (design/16 §4.2)
		// and the frontend can route the delta to the active session.
		ev.SessionID = loopSession(ctx)
		ev.TurnID = loopTurn(ctx)
		// Suppress UI broadcast for internal autonomous passes (backthink),
		// whose intermediate reasoning must not leak into the chat stream, and for
		// thinking frames when the bound persona turned them off (showToUser:
		// false). Both gates are broadcast-only: the response the model produced is
		// unchanged, so display and persistence stay decoupled.
		if l.onStream != nil && !isMutedBroadcast(ctx) && l.broadcasts(ev) {
			l.onStream(ev)
		}
	})
	if err != nil {
		return nil, fmt.Errorf("loop: chat stream: %w", err)
	}

	if l.guards != nil {
		verdict, err := l.guards.CheckOutput(ctx, &resp)
		if err != nil {
			return nil, fmt.Errorf("loop: check output: %w", err)
		}
		if verdict != nil && !verdict.Allow {
			return &stepOutcome{final: true, text: verdict.Reason, stopReason: agent.StopReasonGuardrailOutput}, nil
		}
	}

	if calls, ok := decodeToolCalls(resp); ok {
		return &stepOutcome{final: false, toolCalls: calls, stopReason: agent.StopReasonToolCalls,
			modelStopReason: resp.StopReason, model: resp.Model}, nil
	}
	return &stepOutcome{final: true, text: resp.Content, stopReason: agent.StopReasonStop,
		modelStopReason: resp.StopReason, model: resp.Model}, nil
}

// broadcasts reports whether a streamed event may be pushed to the UI. Only
// thinking frames are ever withheld, and only when the wiring resolved the
// persona's showToUser to false; text, tool-call and tool-progress frames are
// never affected, so turning thinking off cannot change what the client sees of
// the answer itself.
func (l *Loop) broadcasts(ev model.StreamEvent) bool {
	if !isThinkingKind(ev.Kind) {
		return true
	}
	return l.thinkingShow == nil || *l.thinkingShow
}

// isThinkingKind reports whether kind is one of the reasoning segment events.
func isThinkingKind(kind model.StreamKind) bool {
	switch kind {
	case model.StreamKindThinkingStart, model.StreamKindThinkingDelta, model.StreamKindThinkingEnd:
		return true
	default:
		return false
	}
}