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use serde::{Deserialize, Serialize};
use std::fs::File;
use std::io::Read;
use std::path::PathBuf;
use std::time::{SystemTime, UNIX_EPOCH};
use time::{OffsetDateTime, format_description::well_known::Rfc2822};
#[derive(Serialize, Deserialize)]
pub struct Metadata {
pub id: String,
#[serde(alias = "createdOn")]
pub created_on: u64,
}
impl Metadata {
/// Reads `Metadata` from a file or creates a new one.
///
/// This method will create new metadata if it can't read the file,
/// whether it's because of malformed JSON, UTF-8 or because the file
/// is not readable.
pub fn read_or_create(file_path: &PathBuf) -> Metadata {
if let Some(metadata) = Metadata::read_metadata_file(file_path) {
metadata
} else {
let timestamp = SystemTime::now().duration_since(UNIX_EPOCH).map_or_else(
|_| 0,
|duration| u64::try_from(duration.as_millis()).unwrap_or(0),
);
Metadata {
id: timestamp.to_string(),
created_on: timestamp,
}
}
}
/// Returns the metadata `created_on` as an RFC-2822 string.
pub fn created_on_utc(&self) -> Option<String> {
let date =
OffsetDateTime::from_unix_timestamp_nanos((self.created_on * 1_000_000).into()).ok()?;
date.format(&Rfc2822).ok()
}
fn read_metadata_file(file_path: &PathBuf) -> Option<Metadata> {
let mut file = File::open(file_path).ok()?;
let mut contents = String::new();
file.read_to_string(&mut contents).ok()?;
serde_json::from_str(&contents).ok()
}
}
#[cfg(test)]
mod tests {
use std::fs::write;
use super::*;
use test_utilities::*;
#[test]
fn test_reads_metadata_if_file_exists() {
let test_dir = setup_test_dir();
create_test_file(
&test_dir.join("metadata.json"),
"\
{
\"id\": \"cool\",
\"created_on\": 1736105008957
}",
);
let metadata = Metadata::read_or_create(&test_dir.join("metadata.json"));
assert_eq!(metadata.id, "cool");
assert_eq!(metadata.created_on, 1_736_105_008_957);
cleanup_test_dir(&test_dir);
}
#[test]
fn test_creates_metadata_if_file_does_not_exist() {
let test_dir = setup_test_dir();
assert!(!test_dir.join("metadata.json").exists());
let metadata = Metadata::read_or_create(&test_dir.join("metadata.json"));
assert_eq!(metadata.created_on.to_string(), metadata.id);
cleanup_test_dir(&test_dir);
}
#[test]
fn test_creates_metadata_if_file_is_malformed() {
let test_dir = setup_test_dir();
write(test_dir.join("metadata.json"), vec![0xFF, 0xFF]).expect("Failed to write file");
let metadata = Metadata::read_or_create(&test_dir.join("metadata.json"));
assert_eq!(metadata.created_on.to_string(), metadata.id);
cleanup_test_dir(&test_dir);
}
#[test]
fn test_it_returns_created_on_as_rfc_2822_utc() {
let metadata = Metadata {
id: "cool".to_string(),
created_on: 1_736_035_200_000,
};
if let Some(created_on_utc) = metadata.created_on_utc() {
assert_eq!(created_on_utc, "Sun, 05 Jan 2025 00:00:00 +0000");
} else {
panic!("Could not generate RFC-2822 string");
}
}
}
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