git.giacomolli.uk - onechat/blob - journal.go

   1 package main
   2
   3 import (
   4         "bufio"
   5         "context"
   6         "encoding/json"
   7         "errors"
   8         "fmt"
   9         "os"
  10         "path/filepath"
  11 )
  12
  13 // journal appends JSON lines to one file for each day in dir, named
  14 // YYYY-MM-DD.jsonl. It keeps the file of the last day open.
  15 type journal struct {
  16         dir  string
  17         file *os.File
  18         day  string
  19 }
  20
  21 // Write appends line to the file of day and flushes it to the disk.
  22 func (j *journal) Write(day string, line []byte) error {
  23         if day != j.day {
  24                 err := j.Close()
  25                 if err != nil {
  26                         return err
  27                 }
  28
  29                 j.file, err = os.OpenFile(filepath.Join(j.dir, day+".jsonl"), os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o600)
  30                 if err != nil {
  31                         return fmt.Errorf("open day file: %w", err)
  32                 }
  33
  34                 j.day = day
  35         }
  36
  37         _, err := j.file.Write(line)
  38         if err != nil {
  39                 return fmt.Errorf("write line: %w", err)
  40         }
  41
  42         err = j.file.Sync()
  43         if err != nil {
  44                 return fmt.Errorf("flush line: %w", err)
  45         }
  46
  47         return nil
  48 }
  49
  50 // Close closes the open day file.
  51 func (j *journal) Close() error {
  52         if j.file == nil {
  53                 return nil
  54         }
  55
  56         err := j.file.Close()
  57         j.file = nil
  58         j.day = ""
  59         if err != nil {
  60                 return fmt.Errorf("close day file: %w", err)
  61         }
  62
  63         return nil
  64 }
  65
  66 // readLines decodes each line of the day files in dir, oldest day first, and
  67 // gives it to add in file order.
  68 func readLines[T any](ctx context.Context, dir string, add func(T) error) error {
  69         paths, err := filepath.Glob(filepath.Join(dir, "*.jsonl"))
  70         if err != nil {
  71                 return fmt.Errorf("list day files: %w", err)
  72         }
  73
  74         for _, path := range paths {
  75                 err = readFile(ctx, path, add)
  76                 if err != nil {
  77                         return err
  78                 }
  79         }
  80
  81         return nil
  82 }
  83
  84 func readFile[T any](ctx context.Context, path string, add func(T) error) (err error) {
  85         file, err := os.Open(path)
  86         if err != nil {
  87                 return fmt.Errorf("open day file: %w", err)
  88         }
  89
  90         defer func() {
  91                 err = errors.Join(err, file.Close())
  92         }()
  93
  94         scanner := bufio.NewScanner(file)
  95         scanner.Buffer(nil, 1<<30)
  96         for number := 1; scanner.Scan(); number++ {
  97                 if ctx.Err() != nil {
  98                         return ctx.Err()
  99                 }
 100
 101                 var value T
 102                 err = json.Unmarshal(scanner.Bytes(), &value)
 103                 if err == nil {
 104                         err = add(value)
 105                 }
 106
 107                 if err != nil {
 108                         return fmt.Errorf("%s line %d: %w", filepath.Base(path), number, err)
 109                 }
 110         }
 111
 112         err = scanner.Err()
 113         if err != nil {
 114                 return fmt.Errorf("read %s: %w", filepath.Base(path), err)
 115         }
 116
 117         return nil
 118 }