package data

import (
	"strings"

	"git.runcible.io/learning/pulley/internal/validator"
)

type Filters struct {
	Page         int
	PageSize     int
	Sort         string
	SortSafelist []string
}

func ValidateFilters(v *validator.Validator, f Filters) {
	v.Check(f.Page > 0, "page", "must be greater than zero")
	v.Check(f.Page < 10_000_000, "page", "must be a maximum of 10 million")
	v.Check(f.PageSize > 0, "page_size", "must be greater than zero")
	v.Check(f.PageSize <= 100, "page_size", "must be a maximum of 100")
	v.Check(validator.PermittedValue(f.Sort, f.SortSafelist...), "sort", "invalid sort value")
}

// sortColumn checks that the client-provided Sort field matches one of the entries in our safelist
// and if it does, extract the column name from the Sort field.
func (f Filters) sortColumn() string {
	for _, safeValue := range f.SortSafelist {
		if f.Sort == safeValue {
			return strings.TrimPrefix(f.Sort, "-")
		}
	}
	// ValidateFilters should have checked this, but we are extra careful of sql injection.
	panic("unsafe sort parameter: " + f.Sort)
}

// sortDirection returns the sort direction depending on the prefix
// character of the Sort field.
func (f Filters) sortDirection() string {
	if strings.HasPrefix(f.Sort, "-") {
		return "DESC"
	}
	return "ASC"
}

// limit returns the page_size provided as a query param
func (f Filters) limit() int {
	return f.PageSize
}

// offset returns the offset of a pagination query based on
// client's page and page_size query params used.
func (f Filters) offset() int {
	return (f.Page - 1) * f.PageSize
}

type Metadata struct {
	CurrentPage  int `json:"current_page,omitzero"`
	PageSize     int `json:"page_size,omitzero"`
	FirstPage    int `json:"first_page,omitzero"`
	LastPage     int `json:"last_page,omitzero"`
	TotalRecords int `json:"total_records,omitzero"`
}

// calculateMetadata returns a Metadata struct from query results and
// query params used in a request
func calculateMetadata(totalRecords, page, pageSize int) Metadata {
	if totalRecords == 0 {
		return Metadata{}
	}

	return Metadata{
		CurrentPage:  page,
		PageSize:     pageSize,
		FirstPage:    1,
		LastPage:     (totalRecords + pageSize - 1) / pageSize,
		TotalRecords: totalRecords,
	}
}