package operations

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

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

// ErrPlanMismatchStale reports a report written against a plan or a tree that
// is no longer current. It is refused rather than replayed: a contradiction
// observed under plan A says nothing about plan B, and one observed at an
// older commit may already be fixed.
var ErrPlanMismatchStale = errors.New("plan mismatch report is stale")

// RecordPlanMismatch records the report, then decides what happens next.
//
// The order matters. The observation is durable before any phase moves, so a
// reopen that fails partway leaves the reason for it in the log rather than a
// task that moved backwards with nothing explaining why.
//
// The requested action is advisory. Orchestra owns the transition, and a
// request that asks for a replan may still get a human decision instead.
func RecordPlanMismatch(s *store.Store, project registry.Project, taskID string, m domain.PlanMismatch, headSHA string) (domain.Event, error) {
	if err := m.Validate(); err != nil {
		return domain.Event{}, err
	}
	t, ok := s.Task(taskID)
	if !ok {
		return domain.Event{}, domain.ErrNotFound
	}
	if current(t) != domain.WorkPhaseImplement {
		return domain.Event{}, fmt.Errorf("%w: work phase is %s, not implement", domain.ErrInvalid, current(t))
	}
	if m.PlanRef != t.PlanRef {
		return domain.Event{}, fmt.Errorf("%w: it names plan %s but this task now works from %s", ErrPlanMismatchStale, short(m.PlanRef), short(t.PlanRef))
	}
	if headSHA != "" && m.AtSHA != headSHA {
		return domain.Event{}, fmt.Errorf("%w: it was written at %s but the worktree is now at %s", ErrPlanMismatchStale, short(m.AtSHA), short(headSHA))
	}
	if err := planPhaseExists(s, t, m.PhaseID); err != nil {
		return domain.Event{}, err
	}
	payload := map[string]any{
		"plan_ref": m.PlanRef, "phase_id": m.PhaseID, "at_sha": m.AtSHA,
		"observed": m.Observed, "contradicts": m.Contradicts,
		"evidence": m.Evidence, "requested_action": string(m.RequestedAction),
	}
	if t.Lease != nil {
		payload["harness_id"], payload["lease_epoch"] = t.Lease.HarnessID, t.Lease.Epoch
	}
	b, err := json.Marshal(payload)
	if err != nil {
		return domain.Event{}, err
	}
	recorded := domain.Event{ID: domain.NewID(), Type: domain.EventPlanMismatchRecorded, TaskID: taskID, Version: t.Version + 1, Payload: b, Surface: string(authz.System)}
	if err := s.Append(recorded); err != nil {
		return domain.Event{}, err
	}
	// A contradiction about intent is not something reading the repository
	// settles, so it stops for the human rather than reopening. This keeps
	// human authority above the planner and stops every ambiguity from
	// becoming a replan.
	if m.RequestedAction == domain.PlanMismatchHumanDecision {
		if err := blockForPlanMismatch(s, taskID, m); err != nil {
			return domain.Event{}, err
		}
		return recorded, nil
	}
	to := domain.WorkPhasePlan
	if m.RequestedAction == domain.PlanMismatchResearch {
		to = domain.WorkPhaseResearch
	}
	// A project whose path omits the phase cannot reopen into it. Planning
	// again on a project that never plans would strand the task in a phase it
	// has no brief for.
	if !projectHasPhase(project, to) {
		if err := blockForPlanMismatch(s, taskID, m); err != nil {
			return domain.Event{}, err
		}
		return recorded, nil
	}
	if err := reopenPhase(s, taskID, to, m); err != nil {
		return domain.Event{}, err
	}
	return recorded, nil
}

func planPhaseExists(s *store.Store, t domain.Task, phaseID string) error {
	raw, err := s.Artifact(t.PlanRef)
	if err != nil {
		return fmt.Errorf("read accepted plan: %w", err)
	}
	doc, err := workphase.DecodeStoredPlan(raw)
	if err != nil {
		return fmt.Errorf("read accepted plan: %w", err)
	}
	// A legacy plan names no phases, and a mismatch against one is still real
	// information. Only a plan that does declare phases can contradict the
	// caller about which one it means.
	if len(doc.Phases) == 0 {
		return nil
	}
	if _, ok := doc.Phase(phaseID); !ok {
		return fmt.Errorf("%w: the accepted plan has no %s", domain.ErrInvalid, phaseID)
	}
	return nil
}

func projectHasPhase(p registry.Project, phase domain.WorkPhase) bool {
	for _, declared := range p.Phases() {
		if declared == phase {
			return true
		}
	}
	return false
}

// reopenPhase performs the one backward move Orchestra may make. The plan is
// not superseded here: it stays accepted, with its progress intact, until a
// replacement is actually sealed. An abandoned replan therefore costs nothing.
func reopenPhase(s *store.Store, taskID string, to domain.WorkPhase, m domain.PlanMismatch) error {
	t, ok := s.Task(taskID)
	if !ok {
		return domain.ErrNotFound
	}
	b, err := json.Marshal(map[string]any{
		"phase": string(to), "from": string(current(t)),
		"reopen": string(domain.EventPlanMismatchRecorded), "reopen_phase_id": m.PhaseID,
	})
	if err != nil {
		return err
	}
	return s.Append(domain.Event{ID: domain.NewID(), Type: domain.EventWorkPhaseChanged, TaskID: taskID, Version: t.Version + 1, Payload: b, Surface: string(authz.System)})
}

// blockForPlanMismatch hands the contradiction to the human. The packet states
// what was observed and what it contradicts, so the reply is informed rather
// than a guess at what the agent meant.
func blockForPlanMismatch(s *store.Store, taskID string, m domain.PlanMismatch) error {
	t, ok := s.Task(taskID)
	if !ok {
		return domain.ErrNotFound
	}
	packet := fmt.Sprintf(
		"The accepted plan is contradicted by the code.\n\nPhase: %s\nObserved: %s\nThe plan says: %s\n",
		m.PhaseID, oneLine(m.Observed), oneLine(m.Contradicts))
	for _, e := range m.Evidence {
		packet += "- evidence: " + oneLine(e) + "\n"
	}
	packet += "\nReply to say how to proceed. Your reply becomes a recorded decision and outranks the plan. If it resolves the contradiction, the task resumes on the same plan; say so explicitly if you want the plan rewritten instead.\n"
	payload := map[string]any{
		"blocker":         packet,
		"block_reason":    string(domain.BlockReasonPlanMismatch),
		"lifecycle_phase": "awaiting_human",
	}
	fenceToLease(payload, t)
	b, err := json.Marshal(payload)
	if err != nil {
		return err
	}
	return s.Append(domain.Event{ID: domain.NewID(), Type: "TaskBlocked", TaskID: taskID, Version: t.Version + 1, Payload: b, Surface: string(authz.System)})
}

// PlanMismatchAnswered reports whether the human has replied since the task
// stopped on a plan mismatch. The rule is positional, the same one the
// trajectory gate uses: deciding whether a reply semantically resolves a
// contradiction would mean parsing intent, and a wrong parse either strands a
// task the human answered or resumes one they did not.
func PlanMismatchAnswered(s *store.Store, taskID string) bool {
	return blockerAnswered(s, taskID, domain.BlockReasonPlanMismatch)
}

// short renders a ref for a human-readable refusal without dumping 64 hex
// characters into a sentence.
func short(ref string) string {
	if len(ref) > 12 {
		return ref[:12]
	}
	if ref == "" {
		return "none"
	}
	return ref
}