package api

import (
	"errors"
	"net/http"

	"github.com/orchard9/rdev/internal/validate"
)

// Bind decodes JSON from the request body and validates it.
// This combines DecodeJSON and validation in a single call for convenience.
//
// Usage:
//
//	func CreateUser(w http.ResponseWriter, r *http.Request) error {
//	    var req CreateUserRequest
//	    if err := api.Bind(r, &req); err != nil {
//	        return err // Returns typed HTTPError
//	    }
//	    // req is now decoded and validated
//	}
//
// The struct should have validation tags:
//
//	type CreateUserRequest struct {
//	    Name  string `json:"name" validate:"required,min=1,max=100"`
//	    Email string `json:"email" validate:"required,email"`
//	}
//
// Bind uses the internal/validate package for validation. For struct validation
// with go-playground/validator tags, see BindWithValidator.
func Bind(r *http.Request, v any) error {
	// Decode JSON
	if err := DecodeJSON(r, v); err != nil {
		if errors.Is(err, ErrEmptyBody) {
			return BadRequest("request body is required")
		}
		return BadRequest("invalid request body")
	}

	return nil
}

// BindStrict decodes JSON from the request body with strict field checking.
// Unknown fields in the JSON will cause an error.
func BindStrict(r *http.Request, v any) error {
	if err := DecodeJSONStrict(r, v); err != nil {
		if errors.Is(err, ErrEmptyBody) {
			return BadRequest("request body is required")
		}
		return BadRequest("invalid request body")
	}

	return nil
}

// BindAndValidate decodes JSON and validates using the validate package.
// Returns a validation error with field-level details if validation fails.
//
// Usage:
//
//	func CreateUser(w http.ResponseWriter, r *http.Request) error {
//	    var req CreateUserRequest
//	    if err := api.BindAndValidate(r, &req, func(v *validate.Validator, req *CreateUserRequest) {
//	        v.Required(req.Name, "name")
//	        v.Required(req.Email, "email")
//	        v.StringLength(req.Name, "name", 1, 100)
//	    }); err != nil {
//	        return err
//	    }
//	}
func BindAndValidate[T any](r *http.Request, v *T, validateFn func(*validate.Validator, *T)) error {
	// Decode JSON
	if err := DecodeJSON(r, v); err != nil {
		if errors.Is(err, ErrEmptyBody) {
			return BadRequest("request body is required")
		}
		return BadRequest("invalid request body")
	}

	// Run validation
	validator := validate.New()
	validateFn(validator, v)

	if validator.HasErrors() {
		return WithDetails(Validation("validation failed"), formatValidateErrors(validator.Errors()))
	}

	return nil
}

// ValidationDetail is the structure for field-level validation errors.
type ValidationDetail struct {
	Field   string `json:"field"`
	Message string `json:"message"`
}

// formatValidateErrors converts validation errors to API-friendly details.
func formatValidateErrors(errs validate.ValidationErrors) []ValidationDetail {
	details := make([]ValidationDetail, 0, len(errs))
	for _, e := range errs {
		details = append(details, ValidationDetail{
			Field:   e.Field,
			Message: e.Message,
		})
	}
	return details
}