feat(core): implement JSON log parser

crates/core/src/parser/json.rs

@@ -1,8 +1,158 @@
-use crate::types::LogEntry;
+use std::collections::HashMap;
 
-pub fn parse_line(_line: &str) -> Option<LogEntry> {
-    todo!()
+use serde_json::Value;
+
+use crate::types::{LogEntry, LogLevel};
+
+pub fn detect_json_log(line: &str) -> bool {
+    matches!(serde_json::from_str::<Value>(line), Ok(Value::Object(_)))
+}
+
+pub fn parse_line(line: &str) -> Option<LogEntry> {
+    if line.trim().is_empty() {
+        return None;
+    }
+
+    let mut fields: HashMap<String, Value> = serde_json::from_str(line).ok()?;
+
+    let raw_line = line.to_string();
+
+    let timestamp = ["timestamp", "time", "ts", "@timestamp"]
+        .iter()
+        .find_map(|key| fields.remove(*key))
+        .and_then(|v| v.as_str().map(String::from));
+
+    let level = ["level", "lvl", "severity"]
+        .iter()
+        .find_map(|key| fields.remove(*key))
+        .and_then(|v| v.as_str().map(String::from))
+        .map(|s| s.parse::<LogLevel>().unwrap());
+
+    Some(LogEntry {
+        line_number: 0,
+        raw_line,
+        timestamp,
+        level,
+        fields,
+    })
+}
+
+pub fn parse_line_with_number(line: &str, line_number: u64) -> Option<LogEntry> {
+    parse_line(line).map(|mut entry| {
+        entry.line_number = line_number;
+        entry
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_valid_json_log() {
+        let line = r#"{"level":"INFO","message":"hello","timestamp":"2024-01-01T00:00:00Z"}"#;
+        let entry = parse_line(line).unwrap();
+        assert_eq!(entry.raw_line, line);
+        assert_eq!(entry.timestamp, Some("2024-01-01T00:00:00Z".to_string()));
+        assert_eq!(entry.level, Some(LogLevel::Info));
+        assert_eq!(
+            entry.fields.get("message"),
+            Some(&Value::String("hello".to_string()))
+        );
+        assert_eq!(entry.line_number, 0);
+    }
+
+    #[test]
+    fn test_json_missing_fields() {
+        let line = r#"{"message":"just a message"}"#;
+        let entry = parse_line(line).unwrap();
+        assert!(entry.timestamp.is_none());
+        assert!(entry.level.is_none());
+        assert_eq!(
+            entry.fields.get("message"),
+            Some(&Value::String("just a message".to_string()))
+        );
+    }
+
+    #[test]
+    fn test_plain_text() {
+        assert!(parse_line("hello world").is_none());
+    }
+
+    #[test]
+    fn test_empty_line() {
+        assert!(parse_line("").is_none());
+    }
+
+    #[test]
+    fn test_whitespace_line() {
+        assert!(parse_line("   ").is_none());
+    }
+
+    #[test]
+    fn test_json_array() {
+        assert!(!detect_json_log("[1,2,3]"));
+    }
+
+    #[test]
+    fn test_json_string() {
+        assert!(!detect_json_log("\"hello\""));
+    }
+
+    #[test]
+    fn test_json_number() {
+        assert!(!detect_json_log("42"));
+    }
+
+    #[test]
+    fn test_json_null() {
+        assert!(!detect_json_log("null"));
+    }
+
+    #[test]
+    fn test_json_bool() {
+        assert!(!detect_json_log("true"));
+    }
+
+    #[test]
+    fn test_level_variants() {
+        let info_line = r#"{"level":"info"}"#;
+        assert_eq!(parse_line(info_line).unwrap().level, Some(LogLevel::Info));
+
+        let error_line = r#"{"level":"ERROR"}"#;
+        assert_eq!(parse_line(error_line).unwrap().level, Some(LogLevel::Error));
+
+        let warn_line = r#"{"level":"warn"}"#;
+        assert_eq!(parse_line(warn_line).unwrap().level, Some(LogLevel::Warn));
+    }
+
+    #[test]
+    fn test_timestamp_key_names() {
+        for key in &["timestamp", "time", "ts", "@timestamp"] {
+            let line = format!(r#"{{"{key}":"2024-01-01T00:00:00Z"}}"#);
+            let entry = parse_line(&line).unwrap();
+            assert_eq!(
+                entry.timestamp,
+                Some("2024-01-01T00:00:00Z".to_string()),
+                "failed for key: {key}"
+            );
+        }
+    }
+
+    #[test]
+    fn test_parse_line_with_number() {
+        let line = r#"{"level":"DEBUG","message":"test"}"#;
+        let entry = parse_line_with_number(line, 42).unwrap();
+        assert_eq!(entry.line_number, 42);
+        assert_eq!(entry.level, Some(LogLevel::Debug));
+    }
+
+    #[test]
+    fn test_level_key_variants() {
+        for key in &["level", "lvl", "severity"] {
+            let line = format!(r#"{{"{key}":"INFO"}}"#);
+            let entry = parse_line(&line).unwrap();
+            assert_eq!(entry.level, Some(LogLevel::Info), "failed for key: {key}");
+        }
     }
-pub fn detect_json_log(_line: &str) -> bool {
-    todo!()
 }