package execution

import (
	"encoding/json"
	"fmt"
	"time"

	"github.com/kami/hexis/internal/domain"
	"github.com/kami/hexis/internal/provider"
	"github.com/kami/hexis/internal/storage"
)

type Engine struct {
	store    storage.Interface
	registry *provider.Registry
}

func New(store storage.Interface, registry *provider.Registry) *Engine {
	return &Engine{store: store, registry: registry}
}

type ExecuteResult struct {
	Execution *domain.Execution `json:"execution"`
}

func (e *Engine) Execute(req *domain.ExecuteRequest) (*ExecuteResult, error) {
	if req.IdempotencyKey != "" {
		existing, err := e.store.GetExecutionByIdempotencyKey(req.IdempotencyKey)
		if err == nil {
			return &ExecuteResult{Execution: existing}, nil
		}
	}

	capability, err := e.store.GetCapability(req.CapabilityID)
	if err != nil {
		return nil, fmt.Errorf("capability: %w", err)
	}

	if capability.TargetEntityID != "" && capability.TargetEntityID != req.TargetEntityID {
		return nil, domain.ErrCapabilityNotBound
	}

	prov, err := e.registry.Get(capability.Provider)
	if err != nil {
		return nil, fmt.Errorf("provider: %w", err)
	}

	now := time.Now().UTC()
	exec := &domain.Execution{
		ID:                 domain.NewExecutionID(),
		CapabilityID:       req.CapabilityID,
		TargetEntityID:     req.TargetEntityID,
		EntityVersion:      req.EntityVersion,
		Arguments:          req.Arguments,
		RequestedBy:        req.RequestedBy,
		Origin:             req.Origin,
		IdempotencyKey:     req.IdempotencyKey,
		Status:             domain.ExecutionStarted,
		CorrelationID:      req.CorrelationID,
		ResolutionEvidence: req.ResolutionEvidence,
		CreatedAt:          now,
		UpdatedAt:          now,
	}
	if exec.Arguments == nil {
		exec.Arguments = map[string]any{}
	}
	if exec.RequestedBy == nil {
		exec.RequestedBy = map[string]string{}
	}
	if exec.Origin == nil {
		exec.Origin = map[string]string{}
	}

	if err := e.store.CreateExecution(exec); err != nil {
		return nil, err
	}

	e.emitEvent(domain.EventExecutionStarted, exec.ID, map[string]any{
		"capability_id":   req.CapabilityID,
		"target_entity_id": req.TargetEntityID,
		"provider":        capability.Provider,
		"correlation_id":  req.CorrelationID,
	})

	result, execErr := prov.Execute(capability, req)
	exec.UpdatedAt = time.Now().UTC()

	if execErr != nil {
		exec.Status = domain.ExecutionFailed
		exec.Error = execErr.Error()
		exec.Result = map[string]any{"error": execErr.Error()}
		e.emitEvent(domain.EventExecutionFailed, exec.ID, map[string]any{
			"capability_id": req.CapabilityID,
			"error":         execErr.Error(),
		})
	} else {
		exec.Status = domain.ExecutionSucceeded
		exec.Result = result
		e.emitEvent(domain.EventExecutionSucceeded, exec.ID, map[string]any{
			"capability_id": req.CapabilityID,
		})
	}

	if err := e.store.UpdateExecution(exec); err != nil {
		return nil, err
	}

	return &ExecuteResult{Execution: exec}, nil
}

func (e *Engine) ValidateTarget(capabilityID, entityID string) error {
	cap, err := e.store.GetCapability(capabilityID)
	if err != nil {
		return err
	}
	if cap.TargetEntityID != "" && cap.TargetEntityID != entityID {
		return domain.ErrCapabilityNotBound
	}
	return nil
}

func (e *Engine) emitEvent(evtType domain.HexisEventType, entityID string, payload map[string]any) {
	e.store.AppendEvent(&domain.Event{
		ID:        domain.NewEventID(),
		Type:      evtType,
		Timestamp: time.Now().UTC(),
		Payload:   payload,
	})
}

type ResolveRequest struct {
	Query string   `json:"query"`
	Types []string `json:"types,omitempty"`
}

type ResolveResult struct {
	Status     string              `json:"status"`
	Candidates []map[string]any    `json:"candidates,omitempty"`
	EntityID   string              `json:"entity_id,omitempty"`
}

var _ json.Marshaler = (*ResolveResult)(nil)

func (r *ResolveResult) MarshalJSON() ([]byte, error) {
	m := map[string]any{"status": r.Status}
	if r.Candidates != nil {
		m["candidates"] = r.Candidates
	}
	if r.EntityID != "" {
		m["entity_id"] = r.EntityID
	}
	return json.Marshal(m)
}