package agenttask

import (
	"context"
	"fmt"
	"reflect"
	"sort"
)

type workflowDecision struct {
	Activated        bool
	AutoResume       bool
	CommandID        CommandID
	WorkflowRevision WorkflowRevision
}

func (m *Manager) observeWorkflows(ctx context.Context) ([]ProjectID, error) {
	registered, err := m.workflow.RegisteredProjects(ctx)
	if err != nil {
		return nil, err
	}
	sort.Slice(registered, func(left, right int) bool {
		return registered[left] < registered[right]
	})
	active := make([]ProjectID, 0, len(registered))
	seen := make(map[ProjectID]struct{}, len(registered))
	for _, projectID := range registered {
		if _, duplicate := seen[projectID]; duplicate {
			continue
		}
		seen[projectID] = struct{}{}
		snapshot, snapshotErr := m.workflow.Snapshot(ctx, projectID)
		if snapshotErr != nil {
			m.blockProject(ctx, projectID, Blocker{
				Code:      BlockerWorkflowUnavailable,
				Message:   snapshotErr.Error(),
				Retryable: true,
			})
			continue
		}
		if err := validateWorkflowSnapshot(snapshot); err != nil {
			m.blockProject(ctx, projectID, Blocker{
				Code:    BlockerInvalidIdentity,
				Message: err.Error(),
			})
			continue
		}
		if snapshot.ProjectID != projectID {
			m.blockProject(ctx, projectID, Blocker{
				Code:    BlockerInvalidIdentity,
				Message: "workflow adapter returned a different project identity",
			})
			continue
		}
		decision, err := mutateDecision(m, ctx, func(state *ManagerState) (workflowDecision, error) {
			project := state.Projects[projectID]
			if project.ProjectID == "" {
				project = ProjectRecord{
					ProjectID:   projectID,
					WorkspaceID: snapshot.WorkspaceID,
					Status:      ProjectStatusObserved,
					Works:       make(map[WorkUnitID]WorkRecord),
				}
			}
			if project.WorkspaceID != snapshot.WorkspaceID {
				project.Status = ProjectStatusBlocked
				project.Blocker = &Blocker{
					Code:    BlockerInvalidIdentity,
					Message: "registered workspace identity does not match workflow snapshot",
				}
				project.UpdatedAt = m.clock.Now()
				state.Projects[projectID] = project
				return workflowDecision{}, nil
			}
			project.Workflow = pointerWorkflow(snapshot)
			project.UpdatedAt = m.clock.Now()
			if project.Intent == nil {
				project.Status = ProjectStatusObserved
				project.Blocker = nil
				state.Projects[projectID] = project
				return workflowDecision{}, nil
			}
			if project.Intent.WorkflowRevision != snapshot.Revision {
				project.Status = ProjectStatusBlocked
				project.Blocker = &Blocker{
					Code:    BlockerWorkflowRevisionDrift,
					Message: "manual start is pinned to a different workflow revision",
				}
				state.Projects[projectID] = project
				return workflowDecision{
					CommandID:        project.Intent.CommandID,
					WorkflowRevision: project.Intent.WorkflowRevision,
				}, nil
			}
			if project.Status == ProjectStatusStopped {
				state.Projects[projectID] = project
				return workflowDecision{
					CommandID:        project.Intent.CommandID,
					WorkflowRevision: project.Intent.WorkflowRevision,
				}, nil
			}
			interrupted := project.Status == ProjectStatusRunning
			explicitlyStarted := project.Status == ProjectStatusStarted
			if interrupted && !project.Intent.AutoResumeInterrupted {
				project.Status = ProjectStatusStopped
				for id, work := range project.Works {
					if !work.State.Terminal() {
						preStop := work.State
						if preStop != WorkStateStopped {
							work.ResumeStage = preStop
						}
						work.State = WorkStateStopped
						work.UpdatedAt = m.clock.Now()
						project.Works[id] = work
					}
				}
				state.Projects[projectID] = project
				return workflowDecision{
					CommandID:        project.Intent.CommandID,
					WorkflowRevision: project.Intent.WorkflowRevision,
				}, nil
			}
			for _, unit := range snapshot.Units {
				if unit.MilestoneID != project.Intent.MilestoneID {
					continue
				}
				work, exists := project.Works[unit.ID]
				if exists && !reflect.DeepEqual(work.Unit, unit) {
					work.State = WorkStateBlocked
					work.Blocker = &Blocker{
						Code:    BlockerWorkflowRevisionDrift,
						Message: fmt.Sprintf("work unit %q changed under an immutable workflow revision", unit.ID),
					}
					work.UpdatedAt = m.clock.Now()
					project.Works[unit.ID] = work
					continue
				}
				if !exists {
					work = WorkRecord{
						Unit:      cloneUnit(unit),
						State:     WorkStateObserved,
						UpdatedAt: m.clock.Now(),
					}
				}
				if unit.Completed {
					work.State = WorkStateCompleted
					work.CompletionVerified = true
				}
				if explicitlyStarted || work.State == WorkStateStopped || work.ResumeStage != "" {
					recoverStoppedWork(&work)
				} else if interrupted && project.Intent.AutoResumeInterrupted {
					recoverInterruptedWork(&work)
				}
				project.Works[unit.ID] = work
			}
			project.Status = ProjectStatusRunning
			project.Blocker = nil
			project.UpdatedAt = m.clock.Now()
			state.Projects[projectID] = project
			return workflowDecision{
				Activated:        true,
				AutoResume:       interrupted && project.Intent.AutoResumeInterrupted,
				CommandID:        project.Intent.CommandID,
				WorkflowRevision: project.Intent.WorkflowRevision,
			}, nil
		})
		if err != nil {
			return active, err
		}
		m.emit(ctx, Event{
			Type:             EventObserved,
			ProjectID:        projectID,
			WorkspaceID:      snapshot.WorkspaceID,
			CommandID:        decision.CommandID,
			WorkflowRevision: snapshot.Revision,
			Detail:           string(snapshot.Revision),
		})
		if decision.Activated {
			if decision.AutoResume {
				m.emit(ctx, Event{
					Type:             EventAutoResume,
					ProjectID:        projectID,
					WorkspaceID:      snapshot.WorkspaceID,
					CommandID:        decision.CommandID,
					WorkflowRevision: snapshot.Revision,
					Detail:           string(snapshot.Revision),
				})
			}
			active = append(active, projectID)
		}
	}
	return active, nil
}

func recoverStoppedWork(work *WorkRecord) {
	target := work.ResumeStage
	if target == "" {
		target = work.State
	}
	switch target {
	case WorkStatePreparing, WorkStateDispatching:
		work.Attempt++
		work.AttemptID = attemptID(work.Unit.ID, work.Attempt)
		work.Target = nil
		work.ContinuationTarget = nil
		work.Isolation = nil
		work.Submission = nil
		work.Review = nil
		work.ChangeSet = nil
		work.Integration = nil
		work.IntegrationAttempt = 0
		work.Locators = make(map[LocatorKind]LocatorRecord)
		work.Blocker = nil
		work.CompletionVerified = false
		work.State = WorkStateReady
	case WorkStateReady, WorkStateStopped:
		work.State = WorkStateReady
	case WorkStateSubmitted, WorkStateReviewing:
		work.State = WorkStateReviewing
	case WorkStateIntegrating, WorkStatePendingIntegration:
		work.State = WorkStatePendingIntegration
	case WorkStateObserved:
		work.State = WorkStateObserved
	case WorkStateCompleted, WorkStateTerminalDeferred, WorkStateBlocked:
		// stay terminal
	default:
		work.State = WorkStateReady
	}
	work.ResumeStage = ""
}

func recoverInterruptedWork(work *WorkRecord) {
	switch work.State {
	case WorkStatePreparing:
		work.State = WorkStateReady
	case WorkStateDispatching:
		// Durable execution reconciliation decides whether a child is live,
		// submitted, absent, or ambiguous before workflow activation.
	case WorkStateSubmitted:
		work.State = WorkStateReviewing
	case WorkStateReviewing:
		// Review is replayed with the same idempotency key.
	case WorkStateIntegrating:
		work.State = WorkStatePendingIntegration
	}
}

func pointerWorkflow(snapshot ProjectWorkflowSnapshot) *ProjectWorkflowSnapshot {
	value := cloneWorkflow(snapshot)
	return &value
}

func (m *Manager) blockProject(ctx context.Context, projectID ProjectID, blocker Blocker) {
	_ = m.mutate(ctx, func(state *ManagerState) error {
		project := state.Projects[projectID]
		if project.ProjectID == "" {
			project.ProjectID = projectID
			project.Works = make(map[WorkUnitID]WorkRecord)
		}
		project.Status = ProjectStatusBlocked
		project.Blocker = &blocker
		project.UpdatedAt = m.clock.Now()
		state.Projects[projectID] = project
		return nil
	})
	m.emit(ctx, Event{
		Type:      EventBlocked,
		ProjectID: projectID,
		Detail:    string(blocker.Code),
	})
}