package operations

import (
	"encoding/json"
	"errors"
	"fmt"
	"strings"

	"orchestra/internal/authz"
	"orchestra/internal/domain"
	"orchestra/internal/store"
	"orchestra/internal/workphase"
)

// ErrTrajectoryGate reports that a phase change stopped for human
// confirmation. It is not a fault: the work so far is sealed and valid, and
// the human now decides whether the direction is right.
var ErrTrajectoryGate = errors.New("trajectory gate: waiting for the human to confirm the direction")

// maxPacketBytes bounds the gate packet. It travels in the TaskBlocked
// blocker field, which is what notification surfaces already deliver, so the
// human reads the packet where they already read blockers.
const maxPacketBytes = 4000

// trajectoryGateOpen reports whether the human has answered the most recent
// gate for this task.
//
// The rule is positional rather than a flag: a decision recorded after the
// gate was raised is the answer to it. That needs no new task field and
// cannot drift out of sync with the log, and it accepts any wording, which
// matters because an imported comment carries no gate-specific subject.
func trajectoryGateOpen(s *store.Store, taskID string) bool {
	return blockerAnswered(s, taskID, domain.BlockReasonTrajectoryGate)
}

// blockerAnswered reports whether the human has replied since the most recent
// block of this reason.
//
// The rule is positional on purpose. Deciding whether a reply semantically
// answers the question would mean parsing intent, and a wrong parse either
// strands a task the human already answered or resumes one they did not. The
// agent receives both the question and the reply and can see for itself.
func blockerAnswered(s *store.Store, taskID string, reason domain.BlockReason) bool {
	var blockSeq, decisionSeq uint64
	for _, e := range s.Events(0) {
		if e.TaskID != taskID {
			continue
		}
		switch e.Type {
		case "TaskBlocked":
			var p struct {
				BlockReason string `json:"block_reason"`
			}
			if json.Unmarshal(e.Payload, &p) == nil && p.BlockReason == string(reason) {
				blockSeq = e.Seq
			}
		case domain.EventHumanDecisionRecorded:
			decisionSeq = e.Seq
		}
	}
	return blockSeq > 0 && decisionSeq > blockSeq
}

// raiseTrajectoryGate blocks the task and hands the human the packet.
func raiseTrajectoryGate(s *store.Store, t domain.Task, from, to domain.WorkPhase, proposal []byte) error {
	packet, err := TrajectoryGatePacket(s, t, from, to, proposal)
	if err != nil {
		return err
	}
	b, err := json.Marshal(map[string]any{
		"blocker":         packet,
		"block_reason":    string(domain.BlockReasonTrajectoryGate),
		"lifecycle_phase": "awaiting_human",
	})
	if err != nil {
		return err
	}
	e := domain.Event{ID: domain.NewID(), Type: "TaskBlocked", TaskID: t.ID, Version: t.Version + 1, Payload: b, Surface: string(authz.System)}
	if err := s.Append(e); err != nil {
		return err
	}
	return fmt.Errorf("%w (task %s, %s to %s)", ErrTrajectoryGate, t.ID, from, to)
}

// TrajectoryGatePacket renders the human's decision packet from state that
// already exists. It is human-facing, unlike agentctx, and deliberately
// carries no transcript: the human is confirming a direction, not auditing a
// session.
// proposal, when set, is the artifact the finishing phase produced but has
// not sealed yet, which is exactly what the human is being asked about.
func TrajectoryGatePacket(s *store.Store, t domain.Task, from, to domain.WorkPhase, proposal []byte) (string, error) {
	intent, err := s.EffectiveIntent(t.ID)
	if err != nil {
		return "", err
	}
	var b strings.Builder
	fmt.Fprintf(&b, "Trajectory gate: %s to %s needs your confirmation.\n", from, to)
	fmt.Fprintf(&b, "\nGoal: %s\n", oneLine(firstNonEmpty(t.Title, t.Description, "not stated")))
	if len(t.Acceptance) > 0 {
		b.WriteString("\nAcceptance:\n")
		for _, a := range t.Acceptance {
			fmt.Fprintf(&b, "- %s\n", oneLine(a))
		}
	}
	if t.ResearchRef != "" {
		if raw, err := s.Artifact(t.ResearchRef); err == nil {
			if r, err := workphase.DecodeResearch(raw); err == nil {
				b.WriteString("\nWhat research established:\n")
				for _, f := range r.Findings {
					fmt.Fprintf(&b, "- %s (%s)\n", oneLine(f.Claim), oneLine(f.Evidence))
				}
				for _, u := range r.Unknowns {
					fmt.Fprintf(&b, "- still unknown: %s\n", oneLine(u))
				}
			}
		}
	}
	planned := proposal
	if len(planned) == 0 && t.PlanRef != "" {
		if raw, err := s.Artifact(t.PlanRef); err == nil {
			planned = raw
		}
	}
	if len(planned) > 0 {
		{
			if p, err := workphase.DecodePlan(planned); err == nil {
				b.WriteString("\nProposed changes:\n")
				for _, c := range p.Changes {
					fmt.Fprintf(&b, "- %s: %s\n", oneLine(c.Target), oneLine(c.Intent))
				}
				if len(p.Verification) > 0 {
					b.WriteString("\nVerification:\n")
					for _, v := range p.Verification {
						fmt.Fprintf(&b, "- %s\n", oneLine(v))
					}
				}
				if len(p.Risks) > 0 {
					b.WriteString("\nRisks:\n")
					for _, r := range p.Risks {
						fmt.Fprintf(&b, "- %s\n", oneLine(r))
					}
				}
				if len(p.DecisionsNeeded) > 0 {
					b.WriteString("\nOpen decisions for you:\n")
					for _, d := range p.DecisionsNeeded {
						fmt.Fprintf(&b, "- %s\n", oneLine(d))
					}
				}
			}
		}
	}
	if len(intent.Decisions) > 0 {
		b.WriteString("\nYour decisions so far:\n")
		for _, d := range intent.Decisions {
			fmt.Fprintf(&b, "- %s (%s): %s\n", d.Kind, d.Subject, oneLine(d.Value))
		}
	}
	b.WriteString("\nReply to confirm or correct the direction. Your reply becomes a recorded decision and outranks the plan above.\n")
	out := b.String()
	if len(out) > maxPacketBytes {
		out = out[:maxPacketBytes] + "\n(truncated)\n"
	}
	return out, nil
}

func oneLine(s string) string {
	return strings.Join(strings.Fields(strings.ReplaceAll(s, "\n", " ")), " ")
}

func firstNonEmpty(values ...string) string {
	for _, v := range values {
		if strings.TrimSpace(v) != "" {
			return v
		}
	}
	return ""
}

// clearTrajectoryGate returns a gated task to the queue once the human has
// answered. The compensating TaskCorrected names the block it reverses, which
// is the §3.1 rule: a wrong or superseded event is never edited.
func clearTrajectoryGate(s *store.Store, t domain.Task) (domain.Task, error) {
	return clearBlocker(s, t, domain.BlockReasonTrajectoryGate, "gate_cleared")
}

// clearBlocker returns an answered task to the queue. The compensating
// TaskCorrected names the block it reverses, per §3.1: a superseded event is
// never edited.
func clearBlocker(s *store.Store, t domain.Task, reason domain.BlockReason, phase string) (domain.Task, error) {
	var gate domain.Event
	for _, e := range s.Events(0) {
		if e.TaskID != t.ID || e.Type != "TaskBlocked" {
			continue
		}
		var p struct {
			BlockReason string `json:"block_reason"`
		}
		if json.Unmarshal(e.Payload, &p) == nil && p.BlockReason == string(reason) {
			gate = e
		}
	}
	if gate.ID == "" {
		return t, fmt.Errorf("%w: no %s blocker to clear on task %s", domain.ErrInvalid, reason, t.ID)
	}
	b, err := json.Marshal(map[string]any{
		"corrects": gate.ID, "state": string(domain.StateQueued),
		"lifecycle_phase": phase,
	})
	if err != nil {
		return t, err
	}
	if err := s.Append(domain.Event{ID: domain.NewID(), Type: "TaskCorrected", TaskID: t.ID, Version: t.Version + 1, Payload: b, Surface: string(authz.System)}); err != nil {
		return t, err
	}
	updated, ok := s.Task(t.ID)
	if !ok {
		return t, domain.ErrNotFound
	}
	return updated, nil
}