Go movie API tutorial

export AMODB_KEY="YOUR_API_KEY"

mkdir topfilms && cd topfilms
go mod init topfilms
go version

package main

import (
	"fmt"
	"net/http"
	"os"
	"time"
)

func main() {
	url := "https://api.amodb.dev/3/discover/movie?with_genres=878"
	req, _ := http.NewRequest(http.MethodGet, url, nil)
	req.Header.Set("Authorization", "Bearer "+os.Getenv("AMODB_KEY"))
	res, err := (&http.Client{Timeout: 10 * time.Second}).Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	fmt.Println(res.Status)
}

type Movie struct {
	ID          int     `json:"id"`
	Title       string  `json:"title"`
	ReleaseDate string  `json:"release_date"`
	VoteAverage float64 `json:"vote_average"`
	VoteCount   int     `json:"vote_count"`
}

type DiscoverPage struct {
	TotalResults int     `json:"total_results"`
	Results      []Movie `json:"results"`
}

func retryDelay(header string) time.Duration {
	seconds, err := strconv.Atoi(header)
	if err != nil || seconds < 1 {
		seconds = 1
	}
	return time.Duration(min(seconds, 30)) * time.Second
}

package main

import (
	"crypto/sha256"
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"strconv"
	"time"
)

const baseURL = "https://api.amodb.dev/3"

type Movie struct {
	ID          int     `json:"id"`
	Title       string  `json:"title"`
	ReleaseDate string  `json:"release_date"`
	VoteAverage float64 `json:"vote_average"`
	VoteCount   int     `json:"vote_count"`
}

type DiscoverPage struct {
	TotalResults int     `json:"total_results"`
	Results      []Movie `json:"results"`
}

type apiError struct {
	StatusCode    int    `json:"status_code"`
	StatusMessage string `json:"status_message"`
}

type Client struct {
	key      string
	hc       *http.Client
	cacheDir string
}

func NewClient(key string) (*Client, error) {
	base, err := os.UserCacheDir()
	if err != nil {
		base = os.TempDir()
	}
	dir := filepath.Join(base, "amodb-top-films")
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return nil, err
	}
	return &Client{key: key, hc: &http.Client{Timeout: 10 * time.Second}, cacheDir: dir}, nil
}

func (c *Client) Get(path string, query url.Values, ttl time.Duration, out any) error {
	endpoint := baseURL + path + "?" + query.Encode()
	cacheFile := filepath.Join(c.cacheDir, fmt.Sprintf("%x.json", sha256.Sum256([]byte(endpoint))))
	if info, err := os.Stat(cacheFile); err == nil && time.Since(info.ModTime()) < ttl {
		if body, err := os.ReadFile(cacheFile); err == nil {
			return json.Unmarshal(body, out)
		}
	}

	for attempt := 1; attempt <= 3; attempt++ {
		req, err := http.NewRequest(http.MethodGet, endpoint, nil)
		if err != nil {
			return err
		}
		req.Header.Set("Authorization", "Bearer "+c.key)
		res, err := c.hc.Do(req)
		if err != nil {
			return fmt.Errorf("network error: %w", err)
		}
		body, err := io.ReadAll(res.Body)
		res.Body.Close()
		if err != nil {
			return fmt.Errorf("reading reply: %w", err)
		}

		switch {
		case res.StatusCode == http.StatusOK:
			_ = os.WriteFile(cacheFile, body, 0o644)
			return json.Unmarshal(body, out)
		case res.StatusCode == http.StatusTooManyRequests && attempt < 3:
			time.Sleep(retryDelay(res.Header.Get("Retry-After")))
		default:
			return statusError(res.StatusCode, body)
		}
	}
	return errors.New("retries exhausted")
}

func retryDelay(header string) time.Duration {
	seconds, err := strconv.Atoi(header)
	if err != nil || seconds < 1 {
		seconds = 1
	}
	return time.Duration(min(seconds, 30)) * time.Second
}

func statusError(status int, body []byte) error {
	if status == http.StatusUnauthorized {
		return errors.New("401: the key is invalid or suspended, check AMODB_KEY")
	}
	var e apiError
	if json.Unmarshal(body, &e) == nil && e.StatusMessage != "" {
		return fmt.Errorf("amodb returned %d (status_code %d): %s", status, e.StatusCode, e.StatusMessage)
	}
	return fmt.Errorf("amodb returned %d", status)
}

func yearOf(date string) string {
	if len(date) >= 4 {
		return date[:4]
	}
	return "n/a"
}

func main() {
	genre := flag.Int("genre", 878, "genre id, 878 is Science Fiction")
	year := flag.Int("year", 2010, "primary release year")
	limit := flag.Int("n", 10, "how many movies to print, 1 to 20")
	flag.Parse()

	key := os.Getenv("AMODB_KEY")
	if key == "" {
		fmt.Fprintln(os.Stderr, "Set AMODB_KEY first.")
		os.Exit(1)
	}
	client, err := NewClient(key)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}

	query := url.Values{}
	query.Set("language", "en-US")
	query.Set("with_genres", strconv.Itoa(*genre))
	query.Set("primary_release_year", strconv.Itoa(*year))
	query.Set("sort_by", "vote_average.desc")
	query.Set("vote_count.gte", "500")

	var page DiscoverPage
	if err := client.Get("/discover/movie", query, 30*time.Minute, &page); err != nil {
		fmt.Fprintln(os.Stderr, "error:", err)
		os.Exit(1)
	}
	if len(page.Results) == 0 {
		fmt.Println("No movies matched.")
		return
	}
	fmt.Printf("%d movies match, best first:\n", page.TotalResults)
	for i, m := range page.Results {
		if i >= *limit {
			break
		}
		fmt.Printf("%2d. %s (%s) %.1f from %d votes\n", i+1, m.Title, yearOf(m.ReleaseDate), m.VoteAverage, m.VoteCount)
	}
}