chore(refactor): Better organization of the codebase, split modules, update docs, add AGENTS.md

This commit is contained in:
Abimael Martell
2026-02-18 10:16:11 -08:00
parent e9c0737bd8
commit 7328af91bd
27 changed files with 8619 additions and 8232 deletions
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//! Column detection, line grouping, and reading-order layout.
use crate::text_utils::{effective_width, sort_line_items};
use crate::types::{TextItem, TextLine};
/// Represents a column region on a page
#[derive(Debug, Clone)]
pub(crate) struct ColumnRegion {
pub(crate) x_min: f32,
pub(crate) x_max: f32,
}
/// Detect column boundaries on a page using a horizontal projection profile.
///
/// Builds an occupancy histogram across the page width and finds empty valleys
/// (gutters) where no text exists. Validates valleys with vertical consistency
/// checks to avoid false positives.
pub(crate) fn detect_columns(items: &[TextItem], page: u32) -> Vec<ColumnRegion> {
const BIN_WIDTH: f32 = 2.0;
const MIN_GUTTER_WIDTH: f32 = 8.0;
const MIN_VERTICAL_SPAN_RATIO: f32 = 0.30;
const MIN_ITEMS_PER_COLUMN: usize = 10;
const NOISE_FRACTION: f32 = 0.15;
// Get items for this page
let page_items: Vec<&TextItem> = items.iter().filter(|i| i.page == page).collect();
if page_items.is_empty() {
return vec![];
}
// Find page bounds
let x_min = page_items.iter().map(|i| i.x).fold(f32::INFINITY, f32::min);
let x_max = page_items
.iter()
.map(|i| i.x + effective_width(i))
.fold(f32::NEG_INFINITY, f32::max);
let page_width = x_max - x_min;
if page_width < 200.0 {
return vec![ColumnRegion { x_min, x_max }];
}
if page_items.len() < 20 {
return vec![ColumnRegion { x_min, x_max }];
}
// Build occupancy histogram.
// Exclude items wider than 60% of page width — these are spanning items
// (titles, full-width paragraphs) that would fill the gutter and prevent
// detection of partial-page column layouts (e.g. two-column abstracts on
// a page that also has single-column introduction text).
let wide_threshold = page_width * 0.6;
let num_bins = ((page_width / BIN_WIDTH).ceil() as usize).max(1);
let mut histogram = vec![0u32; num_bins];
for item in &page_items {
let w = effective_width(item);
if w > wide_threshold {
continue;
}
let left = ((item.x - x_min) / BIN_WIDTH).floor() as usize;
let right = (((item.x + w) - x_min) / BIN_WIDTH).ceil() as usize;
let left = left.min(num_bins);
let right = right.min(num_bins);
for count in histogram.iter_mut().take(right).skip(left) {
*count += 1;
}
}
// Find the noise threshold: bins with count <= max_count * NOISE_FRACTION are "empty"
let max_count = *histogram.iter().max().unwrap_or(&0);
let noise_threshold = (max_count as f32 * NOISE_FRACTION) as u32;
// Find empty valleys (consecutive runs of low-count bins)
// Each valley is stored as (start_bin, end_bin)
let mut valleys: Vec<(usize, usize)> = Vec::new();
let mut valley_start: Option<usize> = None;
for (i, &count) in histogram.iter().enumerate() {
if count <= noise_threshold {
if valley_start.is_none() {
valley_start = Some(i);
}
} else if let Some(start) = valley_start {
valleys.push((start, i));
valley_start = None;
}
}
// Close any valley that extends to the end
if let Some(start) = valley_start {
valleys.push((start, num_bins));
}
// Filter valleys: must be wide enough and not at page margins
let margin_threshold = page_width * 0.05;
let valleys: Vec<(usize, usize)> = valleys
.into_iter()
.filter(|&(start, end)| {
let width_pts = (end - start) as f32 * BIN_WIDTH;
if width_pts < MIN_GUTTER_WIDTH {
return false;
}
// Valley center must not be within 5% of page edges
let center_pts = ((start + end) as f32 / 2.0) * BIN_WIDTH;
center_pts > margin_threshold && center_pts < (page_width - margin_threshold)
})
.collect();
if valleys.is_empty() {
return vec![ColumnRegion { x_min, x_max }];
}
// Compute Y range of the page
let y_min = page_items.iter().map(|i| i.y).fold(f32::INFINITY, f32::min);
let y_max = page_items
.iter()
.map(|i| i.y)
.fold(f32::NEG_INFINITY, f32::max);
let y_range = y_max - y_min;
// Validate each valley with vertical consistency
let mut valid_valleys: Vec<(usize, usize)> = Vec::new();
for &(start, end) in &valleys {
let gutter_left = x_min + start as f32 * BIN_WIDTH;
let gutter_right = x_min + end as f32 * BIN_WIDTH;
let gutter_center = (gutter_left + gutter_right) / 2.0;
// Collect items on each side of the gutter
let left_items: Vec<&&TextItem> = page_items
.iter()
.filter(|i| i.x + effective_width(i) <= gutter_center)
.collect();
let right_items: Vec<&&TextItem> =
page_items.iter().filter(|i| i.x >= gutter_center).collect();
if left_items.len() < MIN_ITEMS_PER_COLUMN || right_items.len() < MIN_ITEMS_PER_COLUMN {
continue;
}
// Check vertical overlap
if y_range > 0.0 {
let left_y_min = left_items.iter().map(|i| i.y).fold(f32::INFINITY, f32::min);
let left_y_max = left_items
.iter()
.map(|i| i.y)
.fold(f32::NEG_INFINITY, f32::max);
let right_y_min = right_items
.iter()
.map(|i| i.y)
.fold(f32::INFINITY, f32::min);
let right_y_max = right_items
.iter()
.map(|i| i.y)
.fold(f32::NEG_INFINITY, f32::max);
let overlap_min = left_y_min.max(right_y_min);
let overlap_max = left_y_max.min(right_y_max);
let overlap = (overlap_max - overlap_min).max(0.0);
if overlap / y_range < MIN_VERTICAL_SPAN_RATIO {
continue;
}
}
valid_valleys.push((start, end));
}
if valid_valleys.is_empty() {
return vec![ColumnRegion { x_min, x_max }];
}
// Limit to at most 3 gutters (4 columns) — keep the widest if more found
if valid_valleys.len() > 3 {
valid_valleys.sort_by(|a, b| {
let wa = (a.1 - a.0) as f32;
let wb = (b.1 - b.0) as f32;
wb.partial_cmp(&wa).unwrap_or(std::cmp::Ordering::Equal)
});
valid_valleys.truncate(3);
// Re-sort by position (left to right)
valid_valleys.sort_by_key(|v| v.0);
}
// Build column regions from gutter boundaries
let mut columns = Vec::new();
let mut col_start = x_min;
for &(start, end) in &valid_valleys {
let gutter_center = x_min + ((start + end) as f32 / 2.0) * BIN_WIDTH;
columns.push(ColumnRegion {
x_min: col_start,
x_max: gutter_center,
});
col_start = gutter_center;
}
columns.push(ColumnRegion {
x_min: col_start,
x_max,
});
columns
}
/// Determines if a text item spans across multiple column regions (e.g. full-width headers/titles).
fn spans_multiple_columns(item: &TextItem, columns: &[ColumnRegion]) -> bool {
let w = effective_width(item);
let item_right = item.x + w;
let overlap_count = columns
.iter()
.filter(|col| {
let overlap_start = item.x.max(col.x_min);
let overlap_end = item_right.min(col.x_max);
let overlap = (overlap_end - overlap_start).max(0.0);
overlap > (col.x_max - col.x_min) * 0.10 || overlap > 20.0
})
.count();
overlap_count >= 2
}
/// Check if a text item is likely a page number
fn is_page_number(item: &TextItem) -> bool {
let text = item.text.trim();
// Must be 1-4 digits only
if text.is_empty() || text.len() > 4 {
return false;
}
if !text.chars().all(|c| c.is_ascii_digit()) {
return false;
}
// Must be at top or bottom of page.
// US Letter = 792pt, A4 = 841pt. Page numbers are typically in the
// top ~5% or bottom ~12% of the page.
item.y > 720.0 || item.y < 100.0
}
/// Group text items into lines, with multi-column support
/// Detect newspaper-style columns: independent text flows that should be read
/// sequentially (all of col1, then col2) rather than Y-interleaved.
pub(crate) fn is_newspaper_layout(per_column_lines: &[Vec<TextLine>]) -> bool {
if per_column_lines.len() < 2 {
return false;
}
// Each column must independently have substantial content
let min_lines = per_column_lines.iter().map(|c| c.len()).min().unwrap_or(0);
if min_lines < 15 {
return false;
}
// Check Y-collision: count lines in the smallest column that have a
// Y-match in any other column. High collision with many lines = newspaper.
let y_tol = 3.0;
let (smallest_idx, _) = per_column_lines
.iter()
.enumerate()
.min_by_key(|(_, c)| c.len())
.unwrap();
let smallest = &per_column_lines[smallest_idx];
let mut collisions = 0u32;
for line in smallest {
for (ci, col) in per_column_lines.iter().enumerate() {
if ci == smallest_idx {
continue;
}
if col.iter().any(|ol| (ol.y - line.y).abs() < y_tol) {
collisions += 1;
break;
}
}
}
let ratio = collisions as f32 / smallest.len() as f32;
ratio > 0.5
}
/// Split column lines into a core cluster and stragglers.
/// The core is the largest group of consecutive lines separated by normal
/// line spacing. Lines in other groups (header remnants, per-word items from
/// full-width lines) are returned as stragglers.
fn split_column_stragglers(lines: Vec<TextLine>) -> (Vec<TextLine>, Vec<TextLine>) {
if lines.len() < 3 {
return (lines, Vec::new());
}
// Lines are sorted Y descending (top-first). Compute gaps.
let mut gaps: Vec<f32> = Vec::new();
for i in 0..lines.len() - 1 {
gaps.push(lines[i].y - lines[i + 1].y);
}
// Median gap = typical line spacing
let mut sorted_gaps = gaps.clone();
sorted_gaps.sort_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal));
let median_gap = sorted_gaps[sorted_gaps.len() / 2];
// A gap > 3× median (min 30pt) indicates a break between content clusters
let threshold = (median_gap * 3.0).max(30.0);
// Find all split points
let mut split_indices: Vec<usize> = Vec::new();
for (i, &gap) in gaps.iter().enumerate() {
if gap > threshold {
split_indices.push(i);
}
}
if split_indices.is_empty() {
return (lines, Vec::new());
}
// Build segments: (start_line_idx, end_line_idx_exclusive)
let mut segments: Vec<(usize, usize)> = Vec::new();
let mut start = 0usize;
for &si in &split_indices {
segments.push((start, si + 1));
start = si + 1;
}
segments.push((start, lines.len()));
// Find the largest segment (the core cluster)
let (core_seg, _) = segments
.iter()
.enumerate()
.max_by_key(|(_, (s, e))| e - s)
.unwrap();
let (cs, ce) = segments[core_seg];
let mut core = Vec::with_capacity(ce - cs);
let mut stragglers = Vec::new();
for (i, line) in lines.into_iter().enumerate() {
if i >= cs && i < ce {
core.push(line);
} else {
stragglers.push(line);
}
}
(core, stragglers)
}
pub fn group_into_lines(items: Vec<TextItem>) -> Vec<TextLine> {
if items.is_empty() {
return Vec::new();
}
// Filter out page numbers (standalone numbers at top/bottom of page)
let items: Vec<TextItem> = items
.into_iter()
.filter(|item| !is_page_number(item))
.collect();
// Get unique pages
let mut pages: Vec<u32> = items.iter().map(|i| i.page).collect();
pages.sort();
pages.dedup();
let mut all_lines = Vec::new();
for page in pages {
let page_items: Vec<TextItem> = items.iter().filter(|i| i.page == page).cloned().collect();
// Detect columns for this page
let columns = detect_columns(&page_items, page);
if columns.len() <= 1 {
// Single column - use simple sorting
let lines = group_single_column(page_items);
all_lines.extend(lines);
} else {
// Multi-column - separate spanning items from column items
let mut spanning_items: Vec<TextItem> = Vec::new();
let mut column_items: Vec<TextItem> = Vec::new();
for item in &page_items {
if spans_multiple_columns(item, &columns) {
spanning_items.push(item.clone());
} else {
column_items.push(item.clone());
}
}
// Process each column's items independently, preserving column identity.
// Assign each item to the column with greatest horizontal overlap
// (instead of center-point) to avoid gutter mis-assignment.
let mut col_buckets: Vec<Vec<TextItem>> = vec![Vec::new(); columns.len()];
for item in &column_items {
let item_left = item.x;
let item_right = item.x + effective_width(item);
let mut best_col = 0;
let mut best_overlap = f32::NEG_INFINITY;
for (ci, col) in columns.iter().enumerate() {
let overlap = (item_right.min(col.x_max) - item_left.max(col.x_min)).max(0.0);
if overlap > best_overlap {
best_overlap = overlap;
best_col = ci;
}
}
col_buckets[best_col].push(item.clone());
}
let mut per_column_lines: Vec<Vec<TextLine>> = Vec::new();
for col_items in col_buckets {
let lines = group_single_column(col_items);
per_column_lines.push(lines);
}
// Process spanning items as their own group
let spanning_lines = group_single_column(spanning_items);
if is_newspaper_layout(&per_column_lines) {
// Newspaper: columns are independent text flows.
// 1. Split each column into its densest cluster (core) and stragglers
// 2. Use core columns to determine the above/below threshold
// 3. Emit: above items → core columns sequentially → below items
let mut core_columns: Vec<Vec<TextLine>> = Vec::new();
let mut col_stragglers: Vec<Vec<TextLine>> = Vec::new();
for col in per_column_lines {
let (core, stragglers) = split_column_stragglers(col);
core_columns.push(core);
col_stragglers.push(stragglers);
}
// col_top = min of max Y across core columns
let col_top = core_columns
.iter()
.filter(|c| !c.is_empty())
.map(|c| c.iter().map(|l| l.y).fold(f32::NEG_INFINITY, f32::max))
.fold(f32::INFINITY, f32::min);
let margin = 5.0;
let mut above: Vec<TextLine> = Vec::new();
let mut below_spanning: Vec<TextLine> = Vec::new();
// Spanning items: above or below the column region
for line in spanning_lines {
if line.y > col_top + margin {
above.push(line);
} else {
below_spanning.push(line);
}
}
// Column stragglers above col_top go to "above";
// below col_top they stay with their column to avoid
// re-interleaving when sorted by Y.
let mut col_below: Vec<Vec<TextLine>> = vec![Vec::new(); core_columns.len()];
for (ci, stragglers) in col_stragglers.into_iter().enumerate() {
for line in stragglers {
if line.y > col_top + margin {
above.push(line);
} else {
col_below[ci].push(line);
}
}
}
above.sort_by(|a, b| b.y.partial_cmp(&a.y).unwrap_or(std::cmp::Ordering::Equal));
below_spanning
.sort_by(|a, b| b.y.partial_cmp(&a.y).unwrap_or(std::cmp::Ordering::Equal));
all_lines.extend(above);
for col in core_columns {
all_lines.extend(col);
}
for cb in col_below {
all_lines.extend(cb);
}
all_lines.extend(below_spanning);
} else {
// Tabular: Y-interleaved merge — rows at the same Y from
// different columns form a single logical line.
let mut all_page_lines: Vec<TextLine> = Vec::new();
all_page_lines.extend(spanning_lines);
for col_lines in per_column_lines {
all_page_lines.extend(col_lines);
}
// Sort by Y descending (top-first), then by X for same-Y lines
all_page_lines.sort_by(|a, b| {
b.y.partial_cmp(&a.y)
.unwrap_or(std::cmp::Ordering::Equal)
.then(
a.items
.first()
.map(|i| i.x)
.unwrap_or(0.0)
.partial_cmp(&b.items.first().map(|i| i.x).unwrap_or(0.0))
.unwrap_or(std::cmp::Ordering::Equal),
)
});
// Merge lines at the same Y (within tolerance) into single lines
let y_tol = 3.0;
let mut merged: Vec<TextLine> = Vec::new();
for line in all_page_lines {
if let Some(last) = merged.last_mut() {
if last.page == line.page && (last.y - line.y).abs() < y_tol {
last.items.extend(line.items);
sort_line_items(&mut last.items);
continue;
}
}
merged.push(line);
}
all_lines.extend(merged);
}
}
}
all_lines
}
/// Determine if Y-sorting should be used instead of stream order.
/// Returns true if the stream order appears chaotic (items jump around in Y position).
fn should_use_y_sorting(items: &[TextItem]) -> bool {
if items.len() < 5 {
return false; // Not enough items to judge
}
// Sample Y positions from stream order
let y_positions: Vec<f32> = items.iter().map(|i| i.y).collect();
// Count "order violations" - cases where Y increases (going up) when it should decrease
// In proper reading order, Y should generally decrease (top to bottom)
let mut large_jumps_up = 0;
let mut large_jumps_down = 0;
let jump_threshold = 50.0; // Significant Y jump
for window in y_positions.windows(2) {
let delta = window[1] - window[0];
if delta > jump_threshold {
large_jumps_up += 1; // Y increased significantly (jumped up on page)
} else if delta < -jump_threshold {
large_jumps_down += 1; // Y decreased significantly (normal reading direction)
}
}
// If there are many upward jumps relative to downward jumps, order is chaotic
// A well-ordered document should have mostly downward progression
let total_jumps = large_jumps_up + large_jumps_down;
if total_jumps < 3 {
return false; // Not enough jumps to judge
}
// If more than 40% of large jumps are upward, use Y-sorting
let chaos_ratio = large_jumps_up as f32 / total_jumps as f32;
chaos_ratio > 0.4
}
/// Group items from a single column into lines
/// Uses heuristics to decide between PDF stream order and Y-position sorting.
fn group_single_column(items: Vec<TextItem>) -> Vec<TextLine> {
if items.is_empty() {
return Vec::new();
}
// Decide whether to use stream order or Y-sorting
let use_y_sorting = should_use_y_sorting(&items);
let items = if use_y_sorting {
// Sort by Y descending (top to bottom in PDF coords)
let mut sorted = items;
sorted.sort_by(|a, b| {
b.y.partial_cmp(&a.y)
.unwrap_or(std::cmp::Ordering::Equal)
.then(a.x.partial_cmp(&b.x).unwrap_or(std::cmp::Ordering::Equal))
});
sorted
} else {
items
};
// Group items into lines
let mut lines: Vec<TextLine> = Vec::new();
let y_tolerance = 3.0;
for item in items {
// Only check the most recent line for merging
let should_merge = lines.last().is_some_and(|last_line| {
if last_line.page != item.page {
return false;
}
let y_diff = (last_line.y - item.y).abs();
if y_diff >= y_tolerance {
return false;
}
// Check if this looks like a new line despite similar Y:
// If items are at the same X position (left margin) but different Y,
// they're vertically stacked lines, not the same line
let has_y_change = y_diff > 0.5;
if has_y_change {
if let Some(first_item) = last_line.items.first() {
let at_same_x = (item.x - first_item.x).abs() < 5.0;
// If at same X (left margin) with Y change, it's likely a new line
if at_same_x {
return false;
}
// If new item starts significantly to the left with Y change,
// it's a new line (not just out-of-order items on same line)
if let Some(last_item) = last_line.items.last() {
if item.x < last_item.x - 10.0 {
return false;
}
}
}
}
true
});
if should_merge {
// Add to the most recent line
lines.last_mut().unwrap().items.push(item);
} else {
// Create new line
let y = item.y;
let page = item.page;
lines.push(TextLine {
items: vec![item],
y,
page,
});
}
}
// Sort items within each line by X position (direction-aware)
for line in &mut lines {
sort_line_items(&mut line.items);
}
lines
}