wme-stream 0.1.1

//! Streaming utilities for the Wikimedia Enterprise API.
//!
//! This crate provides utilities for processing NDJSON streams from Wikimedia Enterprise
//! APIs (Snapshot and Realtime). It handles deduplication, checkpoint/resume functionality,
//! and efficient streaming parsing.
//!
//! # Overview
//!
//! Wikimedia Enterprise provides data in several formats:
//! - **Snapshot API** - Complete project dumps as `.tar.gz` with NDJSON files
//! - **Realtime API** - Streaming updates via SSE or NDJSON
//! - **Realtime Batch** - Hourly bundles of updates as `.tar.gz`
//!
//! This crate helps you process these data sources efficiently.
//!
//! # Key Features
//!
//! - **NDJSON Streaming** - Parse newline-delimited JSON from any source
//! - **Deduplication** - Handle duplicate articles automatically (keep latest version)
//! - **Checkpoint/Resume** - Save and resume long-running downloads
//! - **Visitor Pattern** - Process articles without full materialization
//! - **Progress Tracking** - Events and statistics for monitoring
//!
//! # Modules
//!
//! - [`ndjson`] - NDJSON parsing from streams and files
//! - [`dedup`] - Duplicate detection and removal
//! - [`checkpoint`] - Resume checkpoint save/load
//! - [`visitor`] - Visitor trait for low-memory processing
//!
//! # Example: Parse NDJSON Stream
//!
//! ```rust,no_run
//! use wme_stream::NdjsonStream;
//! use wme_models::Article;
//! use futures::StreamExt;
//! use std::io::BufReader;
//! use std::fs::File;
//! use std::pin::pin;
//!
//! # async fn example() -> Result<(), Box<dyn std::error::Error>> {
//! // Open NDJSON file
//! let input_file = File::open("articles.ndjson")?;
//! let reader = BufReader::new(input_file);
//!
//! // Create line stream
//! let lines = NdjsonStream::from_reader(reader);
//!
//! // Parse into Articles
//! let articles = NdjsonStream::parse_articles(lines);
//!
//! // Process each article (pin the stream first)
//! let mut pinned = pin!(articles);
//! while let Some(result) = pinned.next().await {
//!     match result {
//!         Ok(article) => println!("{}: {}", article.identifier, article.name),
//!         Err(e) => eprintln!("Error: {}", e),
//!     }
//! }
//! # Ok(())
//! # }
//! ```
//!
//! # Example: Deduplicate Stream
//!
//! ```rust,no_run
//! use wme_stream::dedup_stream;
//! use futures::StreamExt;
//! use std::pin::pin;
//!
//! # async fn example<S>(stream: S)
//! # where
//! #     S: futures::Stream<Item = Result<wme_models::Article, wme_stream::StreamError>>,
//! # {
//! // Wrap stream to deduplicate
//! let deduplicated = dedup_stream(stream);
//!
//! // Pin the stream before iterating
//! let mut pinned = pin!(deduplicated);
//! while let Some(result) = pinned.next().await {
//!     // Only latest version of each article
//!     let _article = result.unwrap();
//! }
//! # }
//! ```
//!
//! # Example: Save/Resume Checkpoint
//!
//! ```rust,no_run
//! use wme_stream::ResumeCheckpoint;
//!
//! # async fn example() -> Result<(), wme_stream::StreamError> {
//! // Save progress after processing 1000 articles
//! let checkpoint = ResumeCheckpoint::new(
//!     "enwiki_namespace_0",
//!     "chunk_0",
//!     5000,  // line offset
//!     1000,  // articles processed
//! );
//! checkpoint.save("/data/checkpoints/").await?;
//!
//! // Later: resume from checkpoint
//! let checkpoint = ResumeCheckpoint::load(
//!     "/data/checkpoints/enwiki_namespace_0.checkpoint.json"
//! ).await?;
//! println!("Resuming from line {}", checkpoint.line_offset);
//! # Ok(())
//! # }
//! ```

#![doc = include_str!("../README.md")]

use std::path::PathBuf;

use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};

pub mod checkpoint;
pub mod dedup;
pub mod ndjson;
pub mod visitor;

pub use checkpoint::ResumeCheckpoint;
pub use dedup::{dedup_collect, dedup_stream};
pub use ndjson::{NdjsonExt, NdjsonStream};
pub use visitor::{ArticleVisitor, NoOpVisitor, StatsVisitor};

/// Progress event for snapshot processing.
///
/// These events allow you to monitor the progress of snapshot downloads
/// and processing. Use them to update progress bars or log activity.
///
/// # Example
///
/// ```rust,compile_only
/// use wme_stream::SnapshotEvent;
///
/// fn handle_event(event: SnapshotEvent) {
///     match event {
///         SnapshotEvent::ChunkStarted { chunk_id, size_bytes } => {
///             println!("Starting download of {} ({} bytes)", chunk_id, size_bytes);
///         }
///         SnapshotEvent::ChunkProgress { chunk_id, bytes_downloaded, bytes_total } => {
///             let pct = (bytes_downloaded as f64 / bytes_total as f64) * 100.0;
///             println!("{}: {:.1}%", chunk_id, pct);
///         }
///         SnapshotEvent::ArticleProcessed { article_id, title } => {
///             println!("Processed: {}", title);
///         }
///         _ => {}
///     }
/// }
/// ```
#[derive(Debug, Clone)]
pub enum SnapshotEvent {
    /// Manifest loaded successfully.
    ManifestLoaded {
        /// Snapshot identifier
        snapshot_id: String,
        /// Number of chunks
        chunks: usize,
    },
    /// Chunk download started.
    ChunkStarted {
        /// Chunk identifier
        chunk_id: String,
        /// Size in bytes
        size_bytes: u64,
    },
    /// Chunk download progress.
    ChunkProgress {
        /// Chunk identifier
        chunk_id: String,
        /// Bytes downloaded so far
        bytes_downloaded: u64,
        /// Total bytes
        bytes_total: u64,
    },
    /// Chunk processing completed.
    ChunkCompleted {
        /// Chunk identifier
        chunk_id: String,
        /// Number of articles processed
        articles_count: u64,
        /// Elapsed time
        elapsed: std::time::Duration,
    },
    /// Individual article processed.
    ArticleProcessed {
        /// Article ID
        article_id: u64,
        /// Article title
        title: String,
    },
    /// Checkpoint saved.
    CheckpointSaved {
        /// Path to checkpoint file
        path: PathBuf,
    },
    /// Error occurred.
    Error {
        /// Error details
        error: StreamError,
        /// Whether the error is recoverable
        recoverable: bool,
    },
    /// Processing completed.
    Completed {
        /// Total articles processed
        total_articles: u64,
        /// Total bytes processed
        total_bytes: u64,
    },
}

/// Errors that can occur during streaming.
///
/// These errors cover IO, parsing, decompression, network, and resume failures.
/// All errors implement `std::error::Error` and are cloneable.
#[derive(thiserror::Error, Debug, Clone)]
pub enum StreamError {
    /// IO error (file read/write).
    #[error("IO error: {0}")]
    Io(String),
    /// JSON parse error.
    #[error("JSON parse error: {0}")]
    JsonParse(String),
    /// Decompression error (tar.gz).
    #[error("Decompression error: {0}")]
    Decompression(String),
    /// Network error.
    #[error("Network error: {0}")]
    Network(String),
    /// Checksum mismatch.
    #[error("Checksum mismatch for {file}")]
    ChecksumMismatch {
        /// File identifier
        file: String,
    },
    /// Resume error (checkpoint load/save).
    #[error("Resume error: {0}")]
    Resume(String),
}

/// Processing statistics.
///
/// Tracks metrics during snapshot/realtime processing including
/// articles processed, bytes transferred, errors, and duplicates.
///
/// # Example
///
/// ```rust
/// use wme_stream::ProcessingStats;
/// use chrono::Utc;
///
/// let mut stats = ProcessingStats::new();
/// stats.articles_processed = 1000;
/// stats.bytes_downloaded = 1024 * 1024 * 100; // 100 MB
///
/// let rate = stats.rate();
/// println!("Processing rate: {} articles/sec", rate);
/// ```
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct ProcessingStats {
    /// Total articles processed
    pub articles_processed: u64,
    /// Total bytes downloaded
    pub bytes_downloaded: u64,
    /// Total bytes decompressed
    pub bytes_decompressed: u64,
    /// Errors encountered
    pub errors: u64,
    /// Duplicates removed
    pub duplicates: u64,
    /// Start time
    pub started_at: Option<DateTime<Utc>>,
    /// End time
    pub completed_at: Option<DateTime<Utc>>,
}

impl ProcessingStats {
    /// Create new empty stats with current timestamp.
    ///
    /// Sets `started_at` to the current time.
    pub fn new() -> Self {
        Self {
            started_at: Some(Utc::now()),
            ..Default::default()
        }
    }

    /// Merge another stats into this one.
    ///
    /// Combines counts from another stats instance. Useful when
    /// aggregating stats from multiple chunks or workers.
    pub fn merge(&mut self, other: &ProcessingStats) {
        self.articles_processed += other.articles_processed;
        self.bytes_downloaded += other.bytes_downloaded;
        self.bytes_decompressed += other.bytes_decompressed;
        self.errors += other.errors;
        self.duplicates += other.duplicates;
    }

    /// Calculate processing rate (articles per second).
    ///
    /// Returns 0.0 if `started_at` is not set.
    /// Uses `completed_at` if set, otherwise uses current time.
    pub fn rate(&self) -> f64 {
        if let Some(started) = self.started_at {
            let duration = self
                .completed_at
                .unwrap_or_else(Utc::now)
                .signed_duration_since(started);
            let seconds = duration.num_seconds() as f64;
            if seconds > 0.0 {
                return self.articles_processed as f64 / seconds;
            }
        }
        0.0
    }

    /// Mark processing as completed.
    ///
    /// Sets `completed_at` to the current time.
    pub fn complete(&mut self) {
        self.completed_at = Some(Utc::now());
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use chrono::Duration;

    #[test]
    fn test_processing_stats_new() {
        let stats = ProcessingStats::new();
        assert!(stats.started_at.is_some());
        assert_eq!(stats.articles_processed, 0);
        assert_eq!(stats.rate(), 0.0); // No time elapsed yet
    }

    #[test]
    fn test_processing_stats_merge() {
        let mut stats1 = ProcessingStats::new();
        stats1.articles_processed = 100;
        stats1.bytes_downloaded = 1000;
        stats1.errors = 5;

        let mut stats2 = ProcessingStats::new();
        stats2.articles_processed = 50;
        stats2.bytes_downloaded = 500;
        stats2.duplicates = 10;

        stats1.merge(&stats2);

        assert_eq!(stats1.articles_processed, 150);
        assert_eq!(stats1.bytes_downloaded, 1500);
        assert_eq!(stats1.errors, 5);
        assert_eq!(stats1.duplicates, 10);
    }

    #[test]
    fn test_processing_stats_rate() {
        let mut stats = ProcessingStats::new();
        stats.started_at = Some(Utc::now() - Duration::seconds(10));
        stats.articles_processed = 100;

        let rate = stats.rate();
        assert!(rate > 0.0);
        assert!((rate - 10.0).abs() < 1.0); // Approximately 10 articles/sec
    }

    #[test]
    fn test_processing_stats_complete() {
        let mut stats = ProcessingStats::new();
        assert!(stats.completed_at.is_none());

        stats.complete();
        assert!(stats.completed_at.is_some());
    }

    #[test]
    fn test_stream_error_display() {
        let err = StreamError::Io("file not found".to_string());
        assert!(err.to_string().contains("IO error"));
        assert!(err.to_string().contains("file not found"));

        let err = StreamError::JsonParse("invalid json".to_string());
        assert!(err.to_string().contains("JSON parse error"));
    }

    #[test]
    fn test_snapshot_event_creation() {
        let event = SnapshotEvent::ManifestLoaded {
            snapshot_id: "enwiki_namespace_0".to_string(),
            chunks: 5,
        };

        match event {
            SnapshotEvent::ManifestLoaded {
                snapshot_id,
                chunks,
            } => {
                assert_eq!(snapshot_id, "enwiki_namespace_0");
                assert_eq!(chunks, 5);
            }
            _ => panic!("Wrong event type"),
        }
    }
}