git.r.bdr.sh - rbdr/mobius/blob - internal/mobius/news.go

   1 package mobius
   2
   3 import (
   4         "fmt"
   5         "io"
   6         "os"
   7         "slices"
   8         "sync"
   9 )
  10
  11 type FlatNews struct {
  12         mu sync.Mutex
  13
  14         data     []byte
  15         filePath string
  16
  17         readOffset int // Internal offset to track read progress
  18 }
  19
  20 func NewFlatNews(path string) (*FlatNews, error) {
  21         data, err := os.ReadFile(path)
  22         if err != nil {
  23                 return &FlatNews{}, err
  24         }
  25
  26         return &FlatNews{
  27                 data:     data,
  28                 filePath: path,
  29         }, nil
  30 }
  31
  32 func (f *FlatNews) Reload() error {
  33         f.mu.Lock()
  34         defer f.mu.Unlock()
  35
  36         data, err := os.ReadFile(f.filePath)
  37         if err != nil {
  38                 return err
  39         }
  40         f.data = data
  41
  42         return nil
  43 }
  44
  45 // It returns the number of bytes read and any error encountered.
  46 func (f *FlatNews) Read(p []byte) (int, error) {
  47         f.mu.Lock()
  48         defer f.mu.Unlock()
  49
  50         if f.readOffset >= len(f.data) {
  51                 return 0, io.EOF // All bytes have been read
  52         }
  53
  54         n := copy(p, f.data[f.readOffset:])
  55
  56         f.readOffset += n
  57
  58         return n, nil
  59 }
  60
  61 // Write implements io.Writer for flat news.
  62 // p is guaranteed to contain the full data of a news post.
  63 func (f *FlatNews) Write(p []byte) (int, error) {
  64         f.mu.Lock()
  65         defer f.mu.Unlock()
  66
  67         f.data = slices.Concat(p, f.data)
  68
  69         tempFilePath := f.filePath + ".tmp"
  70
  71         if err := os.WriteFile(tempFilePath, f.data, 0644); err != nil {
  72                 return 0, fmt.Errorf("write to temporary file: %v", err)
  73         }
  74
  75         // Atomically rename the temporary file to the final file path.
  76         if err := os.Rename(tempFilePath, f.filePath); err != nil {
  77                 return 0, fmt.Errorf("rename temporary file to final file: %v", err)
  78         }
  79
  80         return len(p), os.WriteFile(f.filePath, f.data, 0644)
  81 }
  82
  83 func (f *FlatNews) Seek(offset int64, _ int) (int64, error) {
  84         f.readOffset = int(offset)
  85
  86         return 0, nil
  87 }