rover-fetch 0.1.0

//! Table transformation modes.

use std::future::Future;
use std::path::PathBuf;
use std::pin::Pin;
use std::sync::Arc;

use futures::stream::{self, StreamExt};
use rand::SeedableRng;
use rand::seq::SliceRandom;
use rand_chacha::ChaCha8Rng;
use serde::{Deserialize, Serialize};
use url::Url;

use crate::extractor::options::{SampleStrategy, TablesMode};
use crate::extractor::output::OutputPaths;
use crate::extractor::pipeline::ExtractorError;

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TableTransform {
    pub ordinal: usize,
    pub mode: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub path: Option<PathBuf>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub kept_rows: Option<usize>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub truncated_rows: Option<usize>,
    /// Per-table summary body emitted by `TablesMode::Summarize`. Absent
    /// for every other mode and for tables where the summarizer hook
    /// returned an error (see `fallback_reason`).
    #[serde(skip_serializing_if = "Option::is_none")]
    pub summary_md: Option<String>,
    /// Set in two cases: (1) the per-table summarizer hook failed
    /// entirely — `summary_md` is `None` and the original markdown is
    /// preserved verbatim; (2) the service fell back internally (e.g.
    /// cloud→extractive) — `summary_md` is set to the fallback backend's
    /// output and `fallback_from` is set to the original backend name.
    /// Mirrors `SummarizerError::fallback_reason()` strings.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub fallback_reason: Option<String>,
    /// Backend name that the per-table summarizer fell back FROM, when
    /// the service performed an internal fallback (e.g.
    /// cloud→extractive). Set alongside `summary_md` (body has a
    /// successfully-produced summary, from the fallback backend) AND
    /// `fallback_reason` (why the primary failed). Distinct from the
    /// total-failure case where `summary_md` is `None` and
    /// `fallback_from` is `None`.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub fallback_from: Option<String>,
}

/// Carrier for per-table internal-fallback metadata. Mirrors
/// `crate::summarizer::FallbackInfo` but owned (the static-str `reason`
/// is converted to `String` to keep this module independent of the
/// summarizer crate).
#[derive(Debug, Clone)]
pub struct FallbackInfo {
    pub from: String,
    pub reason: String,
}

/// Async hook the `TablesMode::Summarize` path invokes for each detected
/// table. Receives the plaintext-rendered table block and returns either
/// the summary string plus optional internal-fallback metadata, or an
/// error reason (the string is recorded in
/// `TableTransform.fallback_reason`).
pub type TableSummarizeHook = Arc<
    dyn for<'a> Fn(
            &'a str,
        ) -> Pin<
            Box<dyn Future<Output = Result<(String, Option<FallbackInfo>), String>> + Send + 'a>,
        > + Send
        + Sync,
>;

/// In-order event emitted by [`iterate_tables`]. `Line` carries a
/// non-table line (without its trailing `\n`); `Table` carries the full
/// pipe-table block (header + separator + data rows) and the table's
/// sequential `ordinal`.
enum TableEvent<'a> {
    Line(&'a str),
    Table(Vec<String>, usize),
}

/// Walk `markdown` line by line and invoke `sink` for each non-table
/// line and each detected pipe-table block (with its sequential
/// `ordinal`). The sink decides what to do with the event — push into
/// an output buffer (sync transform) or enqueue for a follow-up await
/// loop (async hook).
///
/// Shared by the sync [`apply`] and the async [`apply_with_summarizer`]
/// so the scanning rules — pipe-table start detection and consecutive
/// `|`-prefixed line collection — cannot drift between the two callers.
fn iterate_tables<F>(markdown: &str, mut sink: F) -> Result<(), ExtractorError>
where
    F: FnMut(TableEvent<'_>) -> Result<(), ExtractorError>,
{
    let mut ordinal: usize = 0;
    let mut iter = markdown.lines().peekable();
    while let Some(line) = iter.next() {
        if is_pipe_table_start(line, iter.peek().copied()) {
            let mut rows: Vec<String> = vec![line.to_string()];
            while let Some(next) = iter.peek().copied() {
                if next.trim_start().starts_with('|') {
                    rows.push(next.to_string());
                    iter.next();
                } else {
                    break;
                }
            }
            sink(TableEvent::Table(rows, ordinal))?;
            ordinal += 1;
        } else {
            sink(TableEvent::Line(line))?;
        }
    }
    Ok(())
}

/// Apply a tables transformation to the markdown, returning the
/// transformed markdown plus per-table records.
///
/// For [`TablesMode::Summarize`], callers MUST use
/// [`apply_with_summarizer`] instead — this synchronous entry point
/// returns an [`ExtractorError`] for that mode because per-table
/// summarization requires an async closure hook. The sync `apply`
/// handles `Embed | Drop | CsvFile | Sample`.
pub fn apply(
    markdown: &str,
    mode: &TablesMode,
    output_paths: &OutputPaths,
    base_url: &Url,
) -> Result<(String, Vec<TableTransform>), ExtractorError> {
    let mut out = String::with_capacity(markdown.len());
    let mut records = Vec::new();

    iterate_tables(markdown, |ev| {
        match ev {
            TableEvent::Line(line) => {
                out.push_str(line);
                out.push('\n');
            }
            TableEvent::Table(rows, ordinal) => {
                let (replacement, record) =
                    transform_table(rows, ordinal, mode, output_paths, base_url)?;
                out.push_str(&replacement);
                out.push('\n');
                if let Some(r) = record {
                    records.push(r);
                }
            }
        }
        Ok(())
    })?;

    if !markdown.ends_with('\n') && out.ends_with('\n') {
        out.pop();
    }
    Ok((out, records))
}

/// Async-aware variant of [`apply`] that routes `TablesMode::Summarize`
/// through `hook`. All other modes delegate to the sync `apply` path.
///
/// For each detected pipe-table the hook is invoked with the table's
/// raw markdown block; on `Ok((summary, fallback))` the block is
/// replaced with the summary text and `TableTransform.summary_md` is
/// populated. If `fallback` is `Some`, the service performed an
/// internal fallback (e.g. cloud→extractive) and the metadata is
/// recorded on the record under `fallback_reason` and `fallback_from`.
/// On `Err(reason)` the original table is preserved verbatim and
/// `fallback_reason` records `reason` (with `fallback_from` left
/// `None`).
pub async fn apply_with_summarizer(
    markdown: &str,
    mode: &TablesMode,
    output_paths: &OutputPaths,
    base_url: &Url,
    hook: Option<&TableSummarizeHook>,
) -> Result<(String, Vec<TableTransform>), ExtractorError> {
    if !matches!(mode, TablesMode::Summarize) {
        return apply(markdown, mode, output_paths, base_url);
    }
    let Some(hook) = hook else {
        return Err(ExtractorError::Metadata(
            "internal: apply_with_summarizer requires a hook for TablesMode::Summarize".into(),
        ));
    };

    // Phase 1: scan synchronously into an in-order event queue. Reuses
    // `iterate_tables` so the scanning rules cannot drift from the sync
    // `apply` path. The hook is async, so we cannot await inside the
    // sync sink — buffer events here and drain in Phase 2.
    enum OwnedEvent {
        Line(String),
        /// `Table(rows, ordinal, table_index)` where `table_index` is the
        /// position of this table in the parallel-hook output vec (see
        /// Phase 2).
        Table(Vec<String>, usize, usize),
    }
    let mut events: Vec<OwnedEvent> = Vec::new();
    let mut tables: Vec<(Vec<String>, usize)> = Vec::new();
    iterate_tables(markdown, |ev| {
        match ev {
            TableEvent::Line(line) => events.push(OwnedEvent::Line(line.to_string())),
            TableEvent::Table(rows, ordinal) => {
                let idx = tables.len();
                tables.push((rows.clone(), ordinal));
                events.push(OwnedEvent::Table(rows, ordinal, idx));
            }
        }
        Ok(())
    })?;

    // Phase 2 (parallel): bound concurrency to 4. Stream ONLY table
    // futures through `buffered(N)` — interleaving immediately-ready
    // `Line` futures starves the bounded buffer (the head Table's
    // pending status blocks pulling further Tables). `buffered` preserves
    // input order, so the resulting `Vec` aligns with the `tables` list
    // and Phase 3 can stitch results back into document order via
    // `table_index`.
    let hook_results: Vec<Result<(String, Option<FallbackInfo>), String>> = stream::iter(tables)
        .map(|(rows, _ordinal)| async move {
            let table_text = rows.join("\n");
            hook(&table_text).await
        })
        .buffered(4)
        .collect()
        .await;

    // Phase 3: stitch the rendered table results back into document
    // order, interleaving with `Line` events.
    let mut out = String::with_capacity(markdown.len());
    let mut records = Vec::new();
    for ev in events {
        match ev {
            OwnedEvent::Line(line) => {
                out.push_str(&line);
                out.push('\n');
            }
            OwnedEvent::Table(rows, ordinal, idx) => {
                let table_text = rows.join("\n");
                match &hook_results[idx] {
                    Ok((summary, fallback)) => {
                        out.push_str(summary);
                        out.push('\n');
                        records.push(TableTransform {
                            ordinal,
                            mode: "summarize".into(),
                            path: None,
                            kept_rows: None,
                            truncated_rows: None,
                            summary_md: Some(summary.clone()),
                            fallback_reason: fallback.as_ref().map(|f| f.reason.clone()),
                            fallback_from: fallback.as_ref().map(|f| f.from.clone()),
                        });
                    }
                    Err(reason) => {
                        out.push_str(&table_text);
                        out.push('\n');
                        records.push(TableTransform {
                            ordinal,
                            mode: "summarize".into(),
                            path: None,
                            kept_rows: None,
                            truncated_rows: None,
                            summary_md: None,
                            fallback_reason: Some(reason.clone()),
                            fallback_from: None,
                        });
                    }
                }
            }
        }
    }
    if !markdown.ends_with('\n') && out.ends_with('\n') {
        out.pop();
    }
    Ok((out, records))
}

fn is_pipe_table_start(line: &str, next: Option<&str>) -> bool {
    if !line.trim_start().starts_with('|') {
        return false;
    }
    let Some(n) = next else {
        return false;
    };
    // Markdown pipe-table separator: |---|---|... or |:---:|...
    let nt = n.trim_start();
    nt.starts_with('|') && nt.chars().all(|c| matches!(c, '|' | '-' | ':' | ' '))
}

fn transform_table(
    rows: Vec<String>,
    ordinal: usize,
    mode: &TablesMode,
    output_paths: &OutputPaths,
    base_url: &Url,
) -> Result<(String, Option<TableTransform>), ExtractorError> {
    match mode {
        TablesMode::Embed => Ok((
            rows.join("\n"),
            Some(TableTransform {
                ordinal,
                mode: "embed".into(),
                path: None,
                kept_rows: None,
                truncated_rows: None,
                summary_md: None,
                fallback_reason: None,
                fallback_from: None,
            }),
        )),
        TablesMode::Drop => Ok((
            format!("_Table {ordinal} omitted_"),
            Some(TableTransform {
                ordinal,
                mode: "drop".into(),
                path: None,
                kept_rows: None,
                truncated_rows: None,
                summary_md: None,
                fallback_reason: None,
                fallback_from: None,
            }),
        )),
        TablesMode::Sample(strategy) => {
            // rows[0] = header, rows[1] = separator, rows[2..] = data
            if rows.len() < 3 {
                return Ok((rows.join("\n"), None));
            }
            let header = &rows[0];
            let sep = &rows[1];
            let data: Vec<&String> = rows[2..].iter().collect();
            let (kept, truncated) = sample_rows(&data, strategy);
            let mut out = vec![header.clone(), sep.clone()];
            for r in &kept {
                out.push((*r).clone());
            }
            if truncated > 0 {
                out.push(format!("_… {truncated} rows truncated …_"));
            }
            Ok((
                out.join("\n"),
                Some(TableTransform {
                    ordinal,
                    mode: "sample".into(),
                    path: None,
                    kept_rows: Some(kept.len()),
                    truncated_rows: Some(truncated),
                    summary_md: None,
                    fallback_reason: None,
                    fallback_from: None,
                }),
            ))
        }
        TablesMode::CsvFile => {
            let path = output_paths.table_path(base_url, ordinal);
            if let Some(parent) = path.parent() {
                std::fs::create_dir_all(parent).map_err(|source| ExtractorError::TableWrite {
                    ordinal,
                    path: parent.display().to_string(),
                    source,
                })?;
            }
            write_csv(&path, &rows, ordinal)?;
            let abs = path.canonicalize().unwrap_or_else(|_| path.clone());
            Ok((
                format!("_Table {ordinal} saved to {}_", abs.display()),
                Some(TableTransform {
                    ordinal,
                    mode: "csv_file".into(),
                    path: Some(abs),
                    kept_rows: None,
                    truncated_rows: None,
                    summary_md: None,
                    fallback_reason: None,
                    fallback_from: None,
                }),
            ))
        }
        TablesMode::Summarize => Err(ExtractorError::Metadata(
            "internal: TablesMode::Summarize must go through apply_with_summarizer".into(),
        )),
    }
}

fn sample_rows<'a>(data: &[&'a String], strategy: &SampleStrategy) -> (Vec<&'a String>, usize) {
    let total = data.len();
    match strategy {
        SampleStrategy::HeadTail { head, tail } => {
            if total <= head + tail {
                return (data.to_vec(), 0);
            }
            let mut kept: Vec<&String> = data.iter().take(*head).copied().collect();
            kept.extend(data.iter().rev().take(*tail).rev().copied());
            let truncated = total - kept.len();
            (kept, truncated)
        }
        SampleStrategy::RandomSeed { rows, seed } => {
            if total <= *rows {
                return (data.to_vec(), 0);
            }
            let mut rng = ChaCha8Rng::seed_from_u64(*seed);
            let mut indices: Vec<usize> = (0..total).collect();
            indices.shuffle(&mut rng);
            indices.truncate(*rows);
            indices.sort();
            let kept: Vec<&String> = indices.iter().map(|i| data[*i]).collect();
            let truncated = total - kept.len();
            (kept, truncated)
        }
    }
}

fn parse_pipe_row(line: &str) -> Vec<String> {
    let line = line.trim();
    let line = line.trim_start_matches('|').trim_end_matches('|');
    line.split('|').map(|c| c.trim().to_string()).collect()
}

fn write_csv(
    path: &std::path::Path,
    rows: &[String],
    ordinal: usize,
) -> Result<(), ExtractorError> {
    let file = std::fs::File::create(path).map_err(|source| ExtractorError::TableWrite {
        ordinal,
        path: path.display().to_string(),
        source,
    })?;
    let mut wtr = csv::Writer::from_writer(file);
    for (i, row) in rows.iter().enumerate() {
        if i == 1 {
            continue; // skip separator
        }
        let cells = parse_pipe_row(row);
        wtr.write_record(&cells)
            .map_err(|e| ExtractorError::TableWrite {
                ordinal,
                path: path.display().to_string(),
                source: std::io::Error::other(e.to_string()),
            })?;
    }
    wtr.flush().map_err(|source| ExtractorError::TableWrite {
        ordinal,
        path: path.display().to_string(),
        source,
    })?;
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::extractor::OUTPUT_DIR_TEST_MUTEX as TEST_MUTEX;

    fn paths() -> OutputPaths {
        let tmp = tempfile::tempdir().unwrap();
        let dir = tmp.path().to_path_buf();
        std::mem::forget(tmp);
        // SAFETY: serialized by TEST_MUTEX in each test
        unsafe { std::env::set_var("ROVER_OUTPUT_DIR", &dir) };
        OutputPaths::resolve(None).unwrap()
    }

    fn url() -> Url {
        Url::parse("https://example.com/").unwrap()
    }

    const TABLE_3ROWS: &str = "| A | B |\n|---|---|\n| 1 | 2 |\n| 3 | 4 |\n| 5 | 6 |";

    #[test]
    fn embed_mode_passes_through() {
        let _g = TEST_MUTEX.lock().unwrap_or_else(|e| e.into_inner());
        let (out, recs) = apply(TABLE_3ROWS, &TablesMode::Embed, &paths(), &url()).unwrap();
        assert!(out.contains("| 1 | 2 |"));
        assert_eq!(recs.len(), 1);
        assert_eq!(recs[0].mode, "embed");
    }

    #[test]
    fn drop_mode_replaces_with_marker() {
        let _g = TEST_MUTEX.lock().unwrap_or_else(|e| e.into_inner());
        let (out, recs) = apply(TABLE_3ROWS, &TablesMode::Drop, &paths(), &url()).unwrap();
        assert!(out.contains("_Table 0 omitted_"));
        assert!(!out.contains("| 1 | 2 |"));
        assert_eq!(recs[0].mode, "drop");
    }

    #[test]
    fn sample_head_tail_keeps_head_plus_tail() {
        let _g = TEST_MUTEX.lock().unwrap_or_else(|e| e.into_inner());
        let strategy = SampleStrategy::HeadTail { head: 1, tail: 1 };
        let (out, recs) =
            apply(TABLE_3ROWS, &TablesMode::Sample(strategy), &paths(), &url()).unwrap();
        assert!(out.contains("| 1 | 2 |"));
        assert!(out.contains("| 5 | 6 |"));
        assert!(out.contains("_… 1 rows truncated …_"));
        assert_eq!(recs[0].kept_rows, Some(2));
        assert_eq!(recs[0].truncated_rows, Some(1));
    }

    #[test]
    fn sample_random_seed_is_deterministic() {
        let _g = TEST_MUTEX.lock().unwrap_or_else(|e| e.into_inner());
        let strat = SampleStrategy::RandomSeed { rows: 2, seed: 42 };
        let (out_a, _) = apply(
            TABLE_3ROWS,
            &TablesMode::Sample(strat.clone()),
            &paths(),
            &url(),
        )
        .unwrap();
        let (out_b, _) = apply(TABLE_3ROWS, &TablesMode::Sample(strat), &paths(), &url()).unwrap();
        assert_eq!(out_a, out_b);
    }

    #[test]
    fn csv_file_writes_table_to_disk_and_replaces_markdown() {
        let _g = TEST_MUTEX.lock().unwrap_or_else(|e| e.into_inner());
        let (out, recs) = apply(TABLE_3ROWS, &TablesMode::CsvFile, &paths(), &url()).unwrap();
        assert!(out.contains("_Table 0 saved to "));
        let p = recs[0].path.as_ref().unwrap();
        let csv = std::fs::read_to_string(p).unwrap();
        assert!(csv.contains("A,B"));
        assert!(csv.contains("1,2"));
        assert!(csv.contains("5,6"));
    }

    #[tokio::test]
    async fn summarize_mode_invokes_hook_per_table() {
        // `paths()` sets `ROVER_OUTPUT_DIR`; serialize against other tests
        // in this module. Drop the guard before awaiting.
        let paths = {
            let _g = TEST_MUTEX.lock().unwrap_or_else(|e| e.into_inner());
            paths()
        };
        let md = "Intro.\n\n| A | B |\n|---|---|\n| 1 | 2 |\n\nMiddle.\n\n| X | Y |\n|---|---|\n| 9 | 8 |\n";
        let counter = std::sync::Arc::new(std::sync::atomic::AtomicUsize::new(0));
        let counter_clone = counter.clone();
        let hook: TableSummarizeHook = std::sync::Arc::new(move |_text: &str| {
            let counter_clone = counter_clone.clone();
            Box::pin(async move {
                counter_clone.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
                Ok::<(String, Option<FallbackInfo>), String>(("(summary)".to_string(), None))
            })
        });
        let (out, recs) =
            apply_with_summarizer(md, &TablesMode::Summarize, &paths, &url(), Some(&hook))
                .await
                .unwrap();
        assert_eq!(counter.load(std::sync::atomic::Ordering::SeqCst), 2);
        assert_eq!(recs.len(), 2);
        assert!(recs.iter().all(|r| r.mode == "summarize"));
        assert!(
            recs.iter()
                .all(|r| r.summary_md.as_deref() == Some("(summary)"))
        );
        assert!(recs.iter().all(|r| r.fallback_reason.is_none()));
        assert!(recs.iter().all(|r| r.fallback_from.is_none()));
        assert!(out.contains("(summary)"));
        assert!(!out.contains("| 1 | 2 |"));
        assert!(!out.contains("| 9 | 8 |"));
    }

    #[tokio::test]
    async fn summarize_mode_records_fallback_when_hook_fails() {
        let paths = {
            let _g = TEST_MUTEX.lock().unwrap_or_else(|e| e.into_inner());
            paths()
        };
        let hook: TableSummarizeHook = std::sync::Arc::new(|_text: &str| {
            Box::pin(async move {
                Err::<(String, Option<FallbackInfo>), String>("auth_failed".to_string())
            })
        });
        let (out, recs) = apply_with_summarizer(
            TABLE_3ROWS,
            &TablesMode::Summarize,
            &paths,
            &url(),
            Some(&hook),
        )
        .await
        .unwrap();
        assert_eq!(recs.len(), 1);
        assert_eq!(recs[0].mode, "summarize");
        assert!(recs[0].summary_md.is_none());
        assert_eq!(recs[0].fallback_reason.as_deref(), Some("auth_failed"));
        assert!(recs[0].fallback_from.is_none());
        assert!(out.contains("| 1 | 2 |"));
        assert!(out.contains("| 5 | 6 |"));
    }

    #[tokio::test]
    async fn summarize_mode_records_internal_fallback_when_hook_returns_fallback_info() {
        let paths = {
            let _g = TEST_MUTEX.lock().unwrap_or_else(|e| e.into_inner());
            paths()
        };
        let hook: TableSummarizeHook = std::sync::Arc::new(|_text: &str| {
            Box::pin(async move {
                Ok::<(String, Option<FallbackInfo>), String>((
                    "(extractive summary)".to_string(),
                    Some(FallbackInfo {
                        from: "fast".to_string(),
                        reason: "backend_unavailable".to_string(),
                    }),
                ))
            })
        });
        let (out, recs) = apply_with_summarizer(
            TABLE_3ROWS,
            &TablesMode::Summarize,
            &paths,
            &url(),
            Some(&hook),
        )
        .await
        .unwrap();
        assert_eq!(recs.len(), 1);
        assert_eq!(recs[0].summary_md.as_deref(), Some("(extractive summary)"));
        assert_eq!(recs[0].fallback_from.as_deref(), Some("fast"));
        assert_eq!(
            recs[0].fallback_reason.as_deref(),
            Some("backend_unavailable")
        );
        assert!(out.contains("(extractive summary)"));
        assert!(!out.contains("| 1 | 2 |"));
    }

    #[test]
    fn non_table_content_passes_through_unchanged() {
        let _g = TEST_MUTEX.lock().unwrap_or_else(|e| e.into_inner());
        let md = "Just some text\n\nNo tables here.\n";
        let (out, recs) = apply(md, &TablesMode::Drop, &paths(), &url()).unwrap();
        assert_eq!(out, md);
        assert!(recs.is_empty());
    }
}