git.r.bdr.sh - rbdr/blog/blob - src/metadata.rs

   1 use std::fs::File;
   2 use std::path::PathBuf;
   3 use std::io::Read;
   4 use std::time::{SystemTime, UNIX_EPOCH};
   5
   6 pub struct Metadata {
   7     pub id: String,
   8     pub created_on: u128
   9 }
  10
  11 impl Metadata {
  12     pub fn serialize(&self) -> String {
  13         format!(r#"{{\n  "id": "{}",\n  "created_on": {}\n}}"#, self.id, self.created_on)
  14     }
  15
  16     pub fn deserialize(input: &str) -> Option<Metadata> {
  17         let clean_input = input
  18             .chars()
  19             .filter(|c| !c.is_whitespace())
  20             .collect::<String>();
  21
  22         let id = Metadata::read_field(&clean_input, "id")?;
  23         let created_on = Metadata::read_field(&clean_input, "createdOn")
  24             .or_else(|| Metadata::read_field(&clean_input, "created_on"))?;
  25
  26         Some(Metadata {
  27             id,
  28             created_on: created_on.parse().ok()?
  29         })
  30     }
  31
  32     pub fn read_or_create(file_path: &PathBuf) -> Metadata {
  33         match Metadata::read_metadata_file(file_path) {
  34             Some(metadata) => metadata,
  35             None => {
  36                 let timestamp = SystemTime::now()
  37                     .duration_since(UNIX_EPOCH)
  38                     .map(|duration| duration.as_millis() as u128)
  39                     .unwrap_or_else(|_| 0);
  40                 return Metadata {
  41                     id: timestamp.to_string(),
  42                     created_on: timestamp
  43                 }
  44             }
  45         }
  46     }
  47
  48     fn read_metadata_file(file_path: &PathBuf) -> Option<Metadata> {
  49         let mut file = File::open(file_path).ok()?;
  50         let mut contents = String::new();
  51         file.read_to_string(&mut contents).ok()?;
  52         Metadata::deserialize(&contents)
  53     }
  54
  55
  56     fn read_field(input: &str, field_name: &str) -> Option<String> {
  57         let key_pattern = format!(r#""{}":""#, field_name);
  58         input.find(&key_pattern)
  59             .and_then(|start| {
  60                 let value_start = start + key_pattern.len();
  61                 let value_end = input[value_start..]
  62                     .find(|c: char| c == ',' || c == '}' || c == '\n')
  63                     .unwrap_or_else(|| input[value_start..].len()) + value_start;
  64
  65                 let raw_value = &input[value_start..value_end];
  66                 let value = raw_value.trim_matches('"').to_string();
  67                 Some(value)
  68             })
  69     }
  70 }