package httpfetcher

import (
	"context"
	"errors"
	"fmt"
	"io/fs"
	"net/http"
	"strings"

	"sneak.berlin/go/pixa/internal/imagerequest"
)

// MockFetcher implements Fetcher using an embedded filesystem.
// Files are organized as: hostname/path/to/file.ext
// The source with host example.com and path /images/photo.jpg maps to
// example.com/images/photo.jpg; the source query is ignored.
type MockFetcher struct {
	fs fs.FS
}

// NewMock creates a new mock fetcher backed by the given filesystem.
func NewMock(fsys fs.FS) *MockFetcher {
	return &MockFetcher{fs: fsys}
}

// Fetch retrieves the source's content from the mock filesystem.
func (m *MockFetcher) Fetch(
	ctx context.Context, source imagerequest.Source,
) (*FetchResult, error) {
	// Check context cancellation
	select {
	case <-ctx.Done():
		return nil, ctx.Err()
	default:
	}

	path := source.Host + source.Path

	// Open the file
	f, err := m.fs.Open(path)
	if err != nil {
		if errors.Is(err, fs.ErrNotExist) {
			return nil, fmt.Errorf("%w: status 404", ErrUpstreamError)
		}

		return nil, fmt.Errorf("failed to open mock file: %w", err)
	}

	// Get file info for content length
	stat, err := f.Stat()
	if err != nil {
		_ = f.Close()

		return nil, fmt.Errorf("failed to stat mock file: %w", err)
	}

	// Detect content type from extension
	contentType := detectContentTypeFromPath(path)

	return &FetchResult{
		Content:       f,
		ContentLength: stat.Size(),
		ContentType:   contentType,
		Headers:       make(http.Header),
	}, nil
}

// The content types the mock fetcher gives files in no format pixa reads.
const (
	contentTypeSVG         = "image/svg+xml"
	contentTypeOctetStream = "application/octet-stream"
)

// detectContentTypeFromPath returns the MIME type based on file extension.
func detectContentTypeFromPath(path string) string {
	path = strings.ToLower(path)

	switch {
	case strings.HasSuffix(path, ".jpg"), strings.HasSuffix(path, ".jpeg"):
		return imagerequest.FormatJPEG.MIMEType()
	case strings.HasSuffix(path, ".png"):
		return imagerequest.FormatPNG.MIMEType()
	case strings.HasSuffix(path, ".gif"):
		return imagerequest.FormatGIF.MIMEType()
	case strings.HasSuffix(path, ".webp"):
		return imagerequest.FormatWebP.MIMEType()
	case strings.HasSuffix(path, ".avif"):
		return imagerequest.FormatAVIF.MIMEType()
	case strings.HasSuffix(path, ".jxl"):
		return imagerequest.FormatJXL.MIMEType()
	case strings.HasSuffix(path, ".svg"):
		return contentTypeSVG
	default:
		return contentTypeOctetStream
	}
}