package protosocket

import (
	"context"
	"encoding/json"
	"errors"

	"github.com/jackc/pgx/v5"

	"github.com/nomadcode/nomadcode-core/internal/storage"
	"github.com/nomadcode/nomadcode-core/internal/workflow"
)

// TaskService is the subset of the workflow service required to map REST task
// semantics onto proto-socket actions.
type TaskService interface {
	CreateTask(context.Context, workflow.CreateTaskInput) (storage.Task, error)
	ListTasks(context.Context, int32) ([]storage.Task, error)
	GetTask(context.Context, string) (storage.Task, error)
	EnqueueTask(context.Context, string) (storage.Task, error)
}

// TaskChannels registers task.* request handlers on a dispatcher.
type TaskChannels struct {
	tasks TaskService
}

func NewTaskChannels(tasks TaskService) *TaskChannels {
	return &TaskChannels{tasks: tasks}
}

func (c *TaskChannels) Register(dispatcher *Dispatcher) {
	dispatcher.Register("task.create", c.handleCreate)
	dispatcher.Register("task.list", c.handleList)
	dispatcher.Register("task.get", c.handleGet)
	dispatcher.Register("task.enqueue", c.handleEnqueue)
}

type listRequest struct {
	Limit int32 `json:"limit"`
}

type idRequest struct {
	ID string `json:"id"`
}

func (c *TaskChannels) handleCreate(ctx context.Context, req Envelope) Envelope {
	input, err := payloadAs[workflow.CreateTaskInput](req.Payload)
	if err != nil {
		return invalidPayloadResponse(req, err)
	}

	task, err := c.tasks.CreateTask(ctx, input)
	if err != nil {
		return mapTaskError(req, err)
	}

	taskMap, err := taskToMap(task)
	if err != nil {
		return ErrorResponse(req, "internal.error", "internal server error", true)
	}

	return SuccessResponse(req, map[string]any{
		"id":                task.ID,
		"status":            task.Status,
		"external_provider": stringOrEmpty(task.ExternalProvider),
		"external_id":       stringOrEmpty(task.ExternalID),
		"task":              taskMap,
	})
}

func (c *TaskChannels) handleList(ctx context.Context, req Envelope) Envelope {
	input, err := payloadAs[listRequest](req.Payload)
	if err != nil {
		return invalidPayloadResponse(req, err)
	}

	tasks, err := c.tasks.ListTasks(ctx, input.Limit)
	if err != nil {
		return mapTaskError(req, err)
	}

	encoded := make([]any, 0, len(tasks))
	for _, task := range tasks {
		taskMap, err := taskToMap(task)
		if err != nil {
			return ErrorResponse(req, "internal.error", "internal server error", true)
		}
		encoded = append(encoded, taskMap)
	}

	return SuccessResponse(req, map[string]any{"tasks": encoded})
}

func (c *TaskChannels) handleGet(ctx context.Context, req Envelope) Envelope {
	input, err := payloadAs[idRequest](req.Payload)
	if err != nil {
		return invalidPayloadResponse(req, err)
	}

	task, err := c.tasks.GetTask(ctx, input.ID)
	if err != nil {
		return mapTaskError(req, err)
	}

	taskMap, err := taskToMap(task)
	if err != nil {
		return ErrorResponse(req, "internal.error", "internal server error", true)
	}

	return SuccessResponse(req, map[string]any{"task": taskMap})
}

func (c *TaskChannels) handleEnqueue(ctx context.Context, req Envelope) Envelope {
	input, err := payloadAs[idRequest](req.Payload)
	if err != nil {
		return invalidPayloadResponse(req, err)
	}

	task, err := c.tasks.EnqueueTask(ctx, input.ID)
	if err != nil {
		return mapTaskError(req, err)
	}

	taskMap, err := taskToMap(task)
	if err != nil {
		return ErrorResponse(req, "internal.error", "internal server error", true)
	}

	return SuccessResponse(req, map[string]any{
		"id":     task.ID,
		"status": task.Status,
		"task":   taskMap,
	})
}

func mapTaskError(req Envelope, err error) Envelope {
	switch {
	case errors.Is(err, workflow.ErrInvalidTaskInput):
		return ErrorResponse(req, "task.invalid_input", err.Error(), false)
	case errors.Is(err, workflow.ErrTaskCannotBeEnqueued):
		return ErrorResponse(req, "task.conflict", err.Error(), false)
	case errors.Is(err, pgx.ErrNoRows):
		return ErrorResponse(req, "task.not_found", "task not found", false)
	default:
		return ErrorResponse(req, "internal.error", "internal server error", true)
	}
}

func invalidPayloadResponse(req Envelope, err error) Envelope {
	return ErrorResponse(req, "task.invalid_payload", "invalid payload: "+err.Error(), false)
}

// payloadAs decodes an envelope payload into a typed request by round-tripping
// through JSON instead of ad hoc map indexing.
func payloadAs[T any](payload map[string]any) (T, error) {
	var out T
	b, err := json.Marshal(payload)
	if err != nil {
		return out, err
	}
	return out, json.Unmarshal(b, &out)
}

func taskToMap(task storage.Task) (map[string]any, error) {
	b, err := json.Marshal(task)
	if err != nil {
		return nil, err
	}
	var out map[string]any
	if err := json.Unmarshal(b, &out); err != nil {
		return nil, err
	}
	return out, nil
}

func stringOrEmpty(value *string) string {
	if value == nil {
		return ""
	}
	return *value
}