package operations

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

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

// DefaultMaxDecisionRequests bounds how many times one task may stop for a
// human question. The bound is per task, not per round: rounds are
// conversation machinery, and one blocker with one question needs none.
const DefaultMaxDecisionRequests = 6

// ErrDecisionBudgetSpent reports that a task has asked its last question. The
// task stays blocked, but for an operator rather than for another answer, so
// an agent cannot turn a task into an interview.
var ErrDecisionBudgetSpent = errors.New("decision request budget spent: operator required")

// RequestHumanDecision records a bounded question and blocks the task on it.
//
// Admission is the agent's judgement, stated in the phase brief: ask only when
// the answer materially changes the implementation, the repository cannot
// answer it, and no useful safe work can continue without guessing. Orchestra
// owns what happens next, which is this function.
func RequestHumanDecision(s *store.Store, project registry.Project, taskID string, req domain.DecisionRequest) (domain.Event, error) {
	if err := req.Validate(); err != nil {
		return domain.Event{}, err
	}
	t, ok := s.Task(taskID)
	if !ok {
		return domain.Event{}, domain.ErrNotFound
	}
	if t.State != domain.StateLeased && t.State != domain.StateNeedsAttention {
		// Only a session that currently owns the task may stop it for a
		// question. Without this, an agent credential is a way to block any
		// task in the queue, including one no agent is working on.
		return domain.Event{}, fmt.Errorf("%w: task %s is not owned by a session (state %s)", domain.ErrConflict, taskID, t.State)
	}
	if t.State == domain.StateBlocked && t.BlockReason == domain.BlockReasonHumanDecision {
		// Already waiting. Re-asking would spam the human and move the
		// position the answered check depends on.
		return domain.Event{}, fmt.Errorf("%w: task %s is already waiting on a decision", domain.ErrConflict, taskID)
	}
	spent := countDecisionRequests(s, taskID)
	if spent >= project.MaxDecisionRequests() {
		e, err := blockTask(s, t, domain.BlockReasonOperatorRequired,
			fmt.Sprintf("This task has asked %d questions, its budget. An operator should look at it rather than answer another.\n\nLast question: %s", spent, req.Question), nil)
		if err != nil {
			return domain.Event{}, err
		}
		return e, fmt.Errorf("%w (task %s, %d requests)", ErrDecisionBudgetSpent, taskID, spent)
	}
	return blockTask(s, t, domain.BlockReasonHumanDecision, req.Render(), &req)
}

func blockTask(s *store.Store, t domain.Task, reason domain.BlockReason, blocker string, req *domain.DecisionRequest) (domain.Event, error) {
	payload := map[string]any{
		"blocker": blocker, "block_reason": string(reason),
		"lifecycle_phase": "awaiting_human",
	}
	if t.Lease != nil {
		// Store.Append fences every lifecycle event on a leased task against
		// the current owner and epoch. A question from a session that no
		// longer owns the task is a conflict, not a block.
		payload["harness_id"] = t.Lease.HarnessID
		payload["lease_epoch"] = t.Lease.Epoch
	}
	if req != nil {
		payload["decision_request"] = req
	}
	b, err := json.Marshal(payload)
	if err != nil {
		return domain.Event{}, err
	}
	e := domain.Event{ID: domain.NewID(), Type: "TaskBlocked", TaskID: t.ID, Version: t.Version + 1, Payload: b, Surface: string(authz.System)}
	return e, s.Append(e)
}

func countDecisionRequests(s *store.Store, taskID string) int {
	n := 0
	for _, e := range s.Events(0) {
		if e.TaskID != taskID || e.Type != "TaskBlocked" {
			continue
		}
		var p struct {
			BlockReason string `json:"block_reason"`
		}
		if json.Unmarshal(e.Payload, &p) == nil && p.BlockReason == string(domain.BlockReasonHumanDecision) {
			n++
		}
	}
	return n
}

// ResumeAnsweredBlockers returns every task whose human blocker has been
// answered to the queue. Run it wherever pending assignment runs: the router
// cannot see a blocked task, so something has to unblock it, and that
// something must be Orchestra rather than the agent that asked.
func ResumeAnsweredBlockers(s *store.Store) ([]domain.Event, error) {
	var out []domain.Event
	for _, t := range s.Tasks() {
		if t.State != domain.StateBlocked {
			continue
		}
		switch t.BlockReason {
		case domain.BlockReasonHumanDecision, domain.BlockReasonTrajectoryGate:
		default:
			// operator_required is deliberately not resumed by a reply. An
			// operator decides when a task that spent its budget continues.
			continue
		}
		if !blockerAnswered(s, t.ID, t.BlockReason) {
			continue
		}
		before := t.Version
		updated, err := clearBlocker(s, t, t.BlockReason, "resumed")
		if err != nil {
			return out, err
		}
		if updated.Version != before {
			out = append(out, domain.Event{ID: t.ID, Type: "TaskCorrected", TaskID: t.ID, Version: updated.Version})
		}
	}
	return out, nil
}

// RecordDeferredFinding keeps a real but out-of-scope discovery without
// derailing the task. It is appended to the log and projected onto nothing,
// so it never enters agent context. Turning these into follow-up tasks is a
// separate, deliberate step.
func RecordDeferredFinding(s *store.Store, taskID string, f domain.DeferredFinding) (domain.Event, error) {
	if err := f.Validate(); err != nil {
		return domain.Event{}, err
	}
	t, ok := s.Task(taskID)
	if !ok {
		return domain.Event{}, domain.ErrNotFound
	}
	b, err := json.Marshal(map[string]any{"summary": f.Summary, "why": f.Why})
	if err != nil {
		return domain.Event{}, err
	}
	e := domain.Event{ID: domain.NewID(), Type: domain.EventDeferredFindingRecorded, TaskID: taskID, Version: t.Version + 1, Payload: b, Surface: string(authz.System)}
	return e, s.Append(e)
}

// DeferredFindings lists what a task chose not to do, for follow-up creation
// at completion time.
func DeferredFindings(s *store.Store, taskID string) []domain.DeferredFinding {
	var out []domain.DeferredFinding
	for _, e := range s.Events(0) {
		if e.TaskID != taskID || e.Type != domain.EventDeferredFindingRecorded {
			continue
		}
		var f domain.DeferredFinding
		if json.Unmarshal(e.Payload, &f) == nil {
			out = append(out, f)
		}
	}
	return out
}