Quick experimentation on how to setup generic restful responses using Go

restful-responses.go

package main

import (
	"encoding/json"
	"fmt"
)

type Formatter interface {
	Format() any
}

type BookModel struct {
	AuthorName string
	BookName string
	ISBN string
	PageCount int
}

func (b BookModel) Format() any {
	type Formatted struct {
		AuthorName string `json:"author_name"`
		BookName string `json:"book_name"`
		ISBN string `json:"isbn"`
		PageCount int `json:"page_count"`
	}

	return Formatted {
		AuthorName: b.AuthorName,
		BookName: b.BookName,
		ISBN: b.ISBN,
		PageCount: b.PageCount,
	}
}

type ResponseList struct {
	Items []any `json:"items"`
	Total int`json:"total"`
	Page int`json:"page"`
	PageSize int`json:"page_size"`
}

func (rl ResponseList) Format() any {
	return rl
}

func main() {
	b := getBooks(20)
	out, err := respondList(b, 12, 1, 12)
	if err != nil {
		panic(err)
	}

	fmt.Printf("out: %+v\n", string(out))
}

func respond[T Formatter](v T) ([]byte, error) {
	return json.MarshalIndent(v.Format(), "", "  ")
}

func respondList[T Formatter](items []T, total, page, pageSize int) ([]byte, error) {
	// format all items first
	formatted := make([]any, len(items))
	for idx := range items {
		formatted[idx] = items[idx].Format()
	}

	// setup response model
	response := ResponseList {
		Items: formatted,
		Page: page,
		PageSize: pageSize,
		Total: total,
	}

	return json.MarshalIndent(response, "", "  ")
}

func getBooks(n int) []BookModel {
	res := make([]BookModel, n)

	for i := 0; i < n; i++ {
		res[i] = getBook()
	}

	return res
}

func getBook() BookModel {
	return BookModel{
		AuthorName: "tables, bobby",
		BookName: "How to drop 'em all",
		ISBN: "123.13.43812.1993",
		PageCount: 12,
	}
}