// Package revalidate pings the frontend's on-demand cache revalidation
// endpoint so sitemap-relevant changes (new signups, content re-seeds) surface
// within seconds instead of waiting out the frontend's daily ISR window.
package revalidate

import (
	"context"
	"fmt"
	"net/http"
	"net/url"
	"time"

	"go.uber.org/zap"
)

// Client posts to <frontend>/api/revalidate. Safe to use when nil or when the
// frontend URL / secret are unset — Trigger becomes a no-op (so dev / misconfig
// never breaks the calling flow).
type Client struct {
	base   string
	secret string
	logger *zap.Logger
}

func New(frontendURL, secret string, logger *zap.Logger) *Client {
	return &Client{
		base:   trimRightSlash(frontendURL),
		secret: secret,
		logger: logger,
	}
}

// Trigger fires a fire-and-forget POST to revalidate the given cache tag.
// Never blocks the caller and never errors out of band — use from request
// handlers (e.g. signup) on a long-lived server.
func (c *Client) Trigger(tag string) {
	if c == nil || c.base == "" || c.secret == "" {
		return
	}
	go func() {
		if err := c.TriggerSync(tag); err != nil && c.logger != nil {
			c.logger.Warn("revalidate ping failed", zap.String("tag", tag), zap.Error(err))
		}
	}()
}

// TriggerSync POSTs synchronously and returns any error. Use from short-lived
// CLIs (e.g. the indexer) that would exit before a background goroutine ran.
// No-op (nil) when the client / URL / secret is unset.
func (c *Client) TriggerSync(tag string) error {
	if c == nil || c.base == "" || c.secret == "" {
		return nil
	}
	endpoint := fmt.Sprintf("%s/api/revalidate?tag=%s&secret=%s",
		c.base, url.QueryEscape(tag), url.QueryEscape(c.secret))
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, nil)
	if err != nil {
		return err
	}
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode >= 300 {
		return fmt.Errorf("revalidate returned %d", resp.StatusCode)
	}
	return nil
}

func trimRightSlash(s string) string {
	for len(s) > 0 && s[len(s)-1] == '/' {
		s = s[:len(s)-1]
	}
	return s
}