Implementing a streaming setup with Usenet

pkg/usenet/nzb.go

@@ -0,0 +1,152 @@
+package usenet
+
+import (
+	"fmt"
+	"strings"
+)
+
+type SegmentRange struct {
+	Segment    NZBSegment // Reference to the segment
+	ByteStart  int64      // Start offset within this segment
+	ByteEnd    int64      // End offset within this segment
+	TotalStart int64      // Absolute start position in file
+	TotalEnd   int64      // Absolute end position in file
+}
+
+func (nzb *NZB) GetFileByName(name string) *NZBFile {
+	for i := range nzb.Files {
+		f := nzb.Files[i]
+		if f.IsDeleted {
+			continue
+		}
+		if nzb.Files[i].Name == name {
+			return &nzb.Files[i]
+		}
+	}
+	return nil
+}
+
+func (nzb *NZB) MarkFileAsRemoved(fileName string) error {
+	for i, file := range nzb.Files {
+		if file.Name == fileName {
+			// Mark the file as deleted
+			nzb.Files[i].IsDeleted = true
+			return nil
+		}
+	}
+	return fmt.Errorf("file %s not found in NZB %s", fileName, nzb.ID)
+}
+
+func (nf *NZBFile) GetSegmentsInRange(segmentSize int64, start, end int64) []SegmentRange {
+	if end == -1 {
+		end = nf.Size - 1
+	}
+
+	var segmentRanges []SegmentRange
+	var cumulativeSize int64
+
+	for i, segment := range nf.Segments {
+		// Use the file's segment size (uniform)
+		if segmentSize <= 0 {
+			segmentSize = segment.Bytes // Fallback to actual segment size if not set
+		}
+
+		// Handle last segment which might be smaller
+		if i == len(nf.Segments)-1 {
+			segmentSize = segment.Bytes // Last segment uses actual size
+		}
+
+		cumulativeSize += segmentSize
+
+		// Skip segments that end before our start position
+		if cumulativeSize <= start {
+			continue
+		}
+
+		// Calculate this segment's boundaries
+		segmentStart := cumulativeSize - segmentSize
+		segmentEnd := cumulativeSize - 1
+
+		// Calculate intersection with requested range
+		rangeStart := max(start, segmentStart)
+		rangeEnd := min(end, segmentEnd)
+
+		segmentRange := SegmentRange{
+			Segment:    segment,
+			ByteStart:  rangeStart - segmentStart, // Offset within segment
+			ByteEnd:    rangeEnd - segmentStart,   // End offset within segment
+			TotalStart: rangeStart,                // Absolute position
+			TotalEnd:   rangeEnd,                  // Absolute position
+		}
+
+		segmentRanges = append(segmentRanges, segmentRange)
+
+		// Stop if we've covered the entire requested range
+		if cumulativeSize >= end+1 {
+			break
+		}
+	}
+
+	return segmentRanges
+}
+
+func (nf *NZBFile) ConvertToSegmentRanges(segments []NZBSegment) []SegmentRange {
+	var segmentRanges []SegmentRange
+	var cumulativeSize int64
+
+	for i, segment := range segments {
+		// Use the file's segment size (uniform)
+		segmentSize := nf.SegmentSize
+
+		// Handle last segment which might be smaller
+		if i == len(segments)-1 {
+			segmentSize = segment.Bytes // Last segment uses actual size
+		}
+
+		cumulativeSize += segmentSize
+
+		segmentRange := SegmentRange{
+			Segment:    segment,
+			ByteStart:  0,                            // Always starts at 0 within the segment
+			ByteEnd:    segmentSize - 1,              // Ends at segment size - 1
+			TotalStart: cumulativeSize - segmentSize, // Absolute start position
+			TotalEnd:   cumulativeSize - 1,           // Absolute end position
+		}
+
+		segmentRanges = append(segmentRanges, segmentRange)
+	}
+
+	return segmentRanges
+}
+
+func (nf *NZBFile) GetCacheKey() string {
+	return fmt.Sprintf("rar_%s_%d", nf.Name, nf.Size)
+}
+
+func (nzb *NZB) GetFiles() []NZBFile {
+	files := make([]NZBFile, 0, len(nzb.Files))
+	for _, file := range nzb.Files {
+		if !file.IsDeleted {
+			files = append(files, file)
+		}
+	}
+	return files[:len(files):len(files)] // Return a slice to avoid aliasing
+}
+
+// ValidateNZB performs basic validation on NZB content
+func ValidateNZB(content []byte) error {
+	if len(content) == 0 {
+		return fmt.Errorf("empty NZB content")
+	}
+
+	// Check for basic XML structure
+	if !strings.Contains(string(content), "<nzb") {
+		return fmt.Errorf("invalid NZB format: missing <nzb> tag")
+	}
+
+	if !strings.Contains(string(content), "<file") {
+		return fmt.Errorf("invalid NZB format: no files found")
+	}
+
+	return nil
+}