feat(api): Expose uptime data as text via API (#758)

* Expose Raw Uptime Data via API

Signed-off-by: James Hillyard <james.hillyard@payara.fish>

* Add Test for Raw Uptime Data API Endpoint

Signed-off-by: James Hillyard <james.hillyard@payara.fish>

* Document Raw Uptime Data API Endpoint

Signed-off-by: James Hillyard <james.hillyard@payara.fish>

* Fix Test after #759 Core Refactor

Signed-off-by: James Hillyard <james.hillyard@payara.fish>

* Update Raw Data Content Type

Signed-off-by: James Hillyard <james.hillyard@payara.fish>

* Support 30d Data from Raw Uptime Endpoint

Signed-off-by: James Hillyard <james.hillyard@payara.fish>

* Update README.md

* Update README.md

---------

Signed-off-by: James Hillyard <james.hillyard@payara.fish>
Co-authored-by: TwiN <twin@linux.com>

api/raw.go

@@ -0,0 +1,43 @@
+package api
+
+import (
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/TwiN/gatus/v5/storage/store"
+	"github.com/TwiN/gatus/v5/storage/store/common"
+	"github.com/gofiber/fiber/v2"
+)
+
+func UptimeRaw(c *fiber.Ctx) error {
+	duration := c.Params("duration")
+	var from time.Time
+	switch duration {
+	case "30d":
+		from = time.Now().Add(-30 * 24 * time.Hour)
+	case "7d":
+		from = time.Now().Add(-7 * 24 * time.Hour)
+	case "24h":
+		from = time.Now().Add(-24 * time.Hour)
+	case "1h":
+		from = time.Now().Add(-2 * time.Hour) // Because uptime metrics are stored by hour, we have to cheat a little
+	default:
+		return c.Status(400).SendString("Durations supported: 30d,7d, 24h, 1h")
+	}
+	key := c.Params("key")
+	uptime, err := store.Get().GetUptimeByKey(key, from, time.Now())
+	if err != nil {
+		if errors.Is(err, common.ErrEndpointNotFound) {
+			return c.Status(404).SendString(err.Error())
+		} else if errors.Is(err, common.ErrInvalidTimeRange) {
+			return c.Status(400).SendString(err.Error())
+		}
+		return c.Status(500).SendString(err.Error())
+	}
+
+	c.Set("Content-Type", "text/plain")
+	c.Set("Cache-Control", "no-cache, no-store, must-revalidate")
+	c.Set("Expires", "0")
+	return c.Status(200).Send([]byte(fmt.Sprintf("%f", uptime)))
+}