package imageprocessor

import (
	"bytes"
	"errors"
	"io"
	"net/http"
	"net/http/httptest"
	"sync/atomic"
	"testing"

	"github.com/davidbyttow/govips/v2/vips"
	"sneak.berlin/go/pixa/internal/imagerequest"
)

// testSVG is a 16x12 SVG, black on its left half and white on its right.
const testSVG = `<svg xmlns="http://www.w3.org/2000/svg" width="16" height="12">` +
	`<rect width="16" height="12" fill="white"/>` +
	`<rect width="8" height="12" fill="black"/></svg>`

// newSVGTestProcessor returns a processor for the SVG tests.
func newSVGTestProcessor() *ImageProcessor {
	return New(Params{MaxInputBytes: 1 << 20, MaxConcurrentProcessing: 1})
}

// processSVG processes svg, as an SVG source, with transform.
func processSVG(
	t *testing.T, svg string, transform imagerequest.Transform,
) (*Result, []byte, error) {
	t.Helper()

	result, err := newSVGTestProcessor().Process(t.Context(),
		bytes.NewReader([]byte(svg)), imagerequest.FormatSVG, &transform)
	if err != nil {
		return nil, nil, err
	}

	output, err := io.ReadAll(result.Content)
	if err != nil {
		t.Fatalf("reading the output: %v", err)
	}

	return result, output, nil
}

// TestImageProcessor_SVGOrigIsTheSVG checks that orig of an SVG at the orig
// size is the SVG itself, never another format, and that orig at another
// size is ErrSVGNotOriginalSize.
func TestImageProcessor_SVGOrigIsTheSVG(t *testing.T) {
	t.Parallel()

	result, output, err := processSVG(t, testSVG,
		imagerequest.Transform{Format: imagerequest.FormatOriginal})
	if err != nil {
		t.Fatalf("orig of the SVG: %v", err)
	}

	t.Logf("orig of the SVG: %s, %dx%d", result.ContentType, result.Width,
		result.Height)

	if result.ContentType != "image/svg+xml" || string(output) != testSVG {
		t.Errorf("orig of the SVG = %s %q, want image/svg+xml %q",
			result.ContentType, output, testSVG)
	}

	_, _, err = processSVG(t, testSVG, imagerequest.Transform{
		Size:   imagerequest.Size{Width: 32, Height: 24},
		Format: imagerequest.FormatOriginal,
	})
	if !errors.Is(err, ErrSVGNotOriginalSize) {
		t.Errorf("orig of the SVG at 32x24: error = %v, want %v", err,
			ErrSVGNotOriginalSize)
	}
}

// TestImageProcessor_RendersSVGToEachRasterFormat checks that an SVG is
// rendered to each raster format at the requested size.
func TestImageProcessor_RendersSVGToEachRasterFormat(t *testing.T) {
	t.Parallel()

	for _, format := range []imagerequest.Format{
		imagerequest.FormatJPEG, imagerequest.FormatPNG, imagerequest.FormatGIF,
		imagerequest.FormatWebP, imagerequest.FormatAVIF, imagerequest.FormatJXL,
	} {
		result, output, err := processSVG(t, testSVG, imagerequest.Transform{
			Size:   imagerequest.Size{Width: 40, Height: 30},
			Format: format,
		})
		if err != nil {
			t.Errorf("SVG as %s: %v", format, err)

			continue
		}

		t.Logf("SVG as %s: %s, %dx%d, %d bytes", format, result.ContentType,
			result.Width, result.Height, len(output))

		if result.ContentType != format.MIMEType() ||
			vips.DetermineImageType(output) != vipsImageType(format) ||
			result.Width != 40 || result.Height != 30 {
			t.Errorf("SVG as %s = %s, %dx%d; want %s, 40x30", format,
				result.ContentType, result.Width, result.Height, format.MIMEType())
		}
	}
}

// TestImageProcessor_RendersSVGSharpWhenEnlarged checks that a 16x12 SVG
// asked for at 1600x1200 is rendered at that size, not rendered at 16x12 and
// enlarged: 10 pixels either side of the edge between its black and white
// halves are black and white, where an enlarged image is grey there.
func TestImageProcessor_RendersSVGSharpWhenEnlarged(t *testing.T) {
	t.Parallel()

	_, output, err := processSVG(t, testSVG, imagerequest.Transform{
		Size:   imagerequest.Size{Width: 1600, Height: 1200},
		Format: imagerequest.FormatPNG,
	})
	if err != nil {
		t.Fatalf("SVG as PNG at 1600x1200: %v", err)
	}

	img, err := vips.NewImageFromBuffer(output)
	if err != nil {
		t.Fatalf("decoding the PNG: %v", err)
	}

	t.Cleanup(img.Close)

	for x, want := range map[int]float64{790: 0, 810: 255} {
		point, err := img.GetPoint(x, 600)
		if err != nil {
			t.Fatalf("GetPoint(%d, 600): %v", x, err)
		}

		t.Logf("pixel at %d,600: %v", x, point)

		if point[0] != want {
			t.Errorf("pixel at %d,600 = %v, want %v", x, point[0], want)
		}
	}
}

// TestImageProcessor_SVGFetchesNothing checks that rendering an SVG that
// refers to an image and an external entity on a local server makes no
// request to that server.
func TestImageProcessor_SVGFetchesNothing(t *testing.T) {
	t.Parallel()

	var requests atomic.Int64

	png := createTestPNG(t, 4, 4)

	server := httptest.NewServer(http.HandlerFunc(
		func(w http.ResponseWriter, r *http.Request) {
			requests.Add(1)
			t.Logf("request for %s", r.URL)
			w.Header().Set("Content-Type", "image/png")
			_, _ = w.Write(png)
		}))
	t.Cleanup(server.Close)

	svg := `<?xml version="1.0"?>` +
		`<!DOCTYPE svg [<!ENTITY outside SYSTEM "` + server.URL + `/entity">]>` +
		`<svg xmlns="http://www.w3.org/2000/svg" ` +
		`xmlns:xlink="http://www.w3.org/1999/xlink" width="16" height="12">` +
		`<image href="` + server.URL + `/image.png" width="16" height="12"/>` +
		`<image xlink:href="` + server.URL + `/xlink.png" width="16" height="12"/>` +
		`<text y="10">&outside;</text></svg>`

	_, _, err := processSVG(t, svg, imagerequest.Transform{
		Format: imagerequest.FormatPNG,
	})
	t.Logf("SVG as PNG: error = %v", err)

	if requests.Load() != 0 {
		t.Errorf("rendering the SVG made %d requests, want none", requests.Load())
	}
}

// TestImageProcessor_RefusesSVGTooLarge checks that an SVG wider than
// MaxInputDimension is ErrInputTooLarge, as a raster source is.
func TestImageProcessor_RefusesSVGTooLarge(t *testing.T) {
	t.Parallel()

	_, _, err := processSVG(t,
		`<svg xmlns="http://www.w3.org/2000/svg" width="10000" height="10"/>`,
		imagerequest.Transform{
			Size:   imagerequest.Size{Width: 100, Height: 100},
			Format: imagerequest.FormatPNG,
		})
	if !errors.Is(err, ErrInputTooLarge) {
		t.Errorf("SVG of 10000x10: error = %v, want %v", err, ErrInputTooLarge)
	}
}

// TestSVGDensity checks the density at which an SVG is rendered to cover
// an output size, and that it is held to MaxInputDimension.
func TestSVGDensity(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name                      string
		width, height             int
		outputWidth, outputHeight int
		want                      int
	}{
		{"own size", 16, 12, 16, 12, svgDefaultDensity},
		{"100 times larger", 16, 12, 1600, 1200, 7200},
		{"wider than the SVG's proportions", 16, 12, 160, 12, 720},
		{"10 times smaller", 100, 100, 10, 10, 8},
		{"held to MaxInputDimension", 8192, 1, 8192, 8192, svgDefaultDensity},
		{"held to MaxInputDimension when enlarged", 1024, 1, 8192, 8192, 576},
	}

	for _, tt := range tests {
		got := svgDensity(tt.width, tt.height, tt.outputWidth, tt.outputHeight)
		if got != tt.want {
			t.Errorf("%s: svgDensity(%d, %d, %d, %d) = %d, want %d", tt.name,
				tt.width, tt.height, tt.outputWidth, tt.outputHeight, got, tt.want)
		}
	}
}