//! Core line-to-markdown conversion loop with table/image interleaving.

use std::collections::HashSet;

use crate::types::TextLine;

use super::analysis::{
    calculate_font_stats, compute_heading_tiers, compute_paragraph_threshold, detect_header_level,
    has_dot_leaders,
};
use super::classify::{format_list_item, is_caption_line, is_list_item, is_monospace_font};
use super::postprocess::clean_markdown;
use super::preprocess::{merge_drop_caps, merge_heading_lines};
use super::MarkdownOptions;

/// Merge continuation tables that span across page breaks.
///
/// When consecutive pages each have exactly one table with the same number of columns
/// AND both pages are table-only (no non-table text), treat them as a single table.
/// We strip their header+separator rows and append their data rows to the first page's
/// table, then remove them from later pages.
pub(super) fn merge_continuation_tables(
    page_tables: &mut std::collections::HashMap<u32, Vec<(f32, String)>>,
    table_only_pages: &HashSet<u32>,
) {
    let mut sorted_pages: Vec<u32> = page_tables.keys().copied().collect();
    sorted_pages.sort();

    if sorted_pages.len() < 2 {
        return;
    }

    // Find runs of consecutive pages that each have exactly one table with matching columns
    let mut i = 0;
    while i < sorted_pages.len() {
        let first_page = sorted_pages[i];
        let first_tables = match page_tables.get(&first_page) {
            Some(t) if t.len() == 1 => t,
            _ => {
                i += 1;
                continue;
            }
        };

        // First page must be table-only to start a merge chain
        if !table_only_pages.contains(&first_page) {
            i += 1;
            continue;
        }

        let first_col_count = count_table_columns(&first_tables[0].1);
        if first_col_count == 0 {
            i += 1;
            continue;
        }

        // Collect continuation pages (must also be table-only)
        let mut continuation_pages = Vec::new();
        let mut j = i + 1;
        while j < sorted_pages.len() {
            let next_page = sorted_pages[j];
            // Must be consecutive page numbers
            let prev_page = if continuation_pages.is_empty() {
                first_page
            } else {
                *continuation_pages.last().unwrap()
            };
            if next_page != prev_page + 1 {
                break;
            }

            // Continuation page must be table-only
            if !table_only_pages.contains(&next_page) {
                break;
            }

            let next_tables = match page_tables.get(&next_page) {
                Some(t) if t.len() == 1 => t,
                _ => break,
            };

            let next_col_count = count_table_columns(&next_tables[0].1);
            if next_col_count != first_col_count {
                break;
            }

            continuation_pages.push(next_page);
            j += 1;
        }

        if !continuation_pages.is_empty() {
            // Collect data rows from continuation pages
            let mut extra_rows = String::new();
            for &cont_page in &continuation_pages {
                if let Some(tables) = page_tables.get(&cont_page) {
                    let table_md = &tables[0].1;
                    // Skip header row (line 1) and separator row (line 2), keep the rest
                    for (line_idx, line) in table_md.lines().enumerate() {
                        if line_idx >= 2 {
                            extra_rows.push_str(line);
                            extra_rows.push('\n');
                        }
                    }
                }
            }

            // Append continuation rows to the first page's table
            if let Some(tables) = page_tables.get_mut(&first_page) {
                tables[0].1.push_str(&extra_rows);
            }

            // Remove continuation pages from the map
            for &cont_page in &continuation_pages {
                page_tables.remove(&cont_page);
            }

            // Skip past the merged pages
            i = j;
        } else {
            i += 1;
        }
    }
}

/// Count the number of columns in a markdown table by counting `|` in the separator row.
fn count_table_columns(table_md: &str) -> usize {
    // The separator row is the second line, containing "| --- | --- |"
    if let Some(sep_line) = table_md.lines().nth(1) {
        if sep_line.contains("---") {
            // Count cells: number of | minus 1 (leading |), but handle edge cases
            let pipes = sep_line.chars().filter(|&c| c == '|').count();
            return if pipes >= 2 { pipes - 1 } else { 0 };
        }
    }
    0
}

/// Flush any remaining tables and images for a given page
fn flush_page_tables_and_images(
    page: u32,
    page_tables: &std::collections::HashMap<u32, Vec<(f32, String)>>,
    page_images: &std::collections::HashMap<u32, Vec<(f32, String)>>,
    inserted_tables: &mut HashSet<(u32, usize)>,
    inserted_images: &mut HashSet<(u32, usize)>,
    output: &mut String,
    in_paragraph: &mut bool,
) {
    if let Some(tables) = page_tables.get(&page) {
        for (idx, (_, table_md)) in tables.iter().enumerate() {
            if !inserted_tables.contains(&(page, idx)) {
                if *in_paragraph {
                    output.push_str("\n\n");
                    *in_paragraph = false;
                }
                output.push('\n');
                output.push_str(table_md);
                output.push('\n');
                inserted_tables.insert((page, idx));
            }
        }
    }
    if let Some(images) = page_images.get(&page) {
        for (idx, (_, image_md)) in images.iter().enumerate() {
            if !inserted_images.contains(&(page, idx)) {
                if *in_paragraph {
                    output.push_str("\n\n");
                    *in_paragraph = false;
                }
                output.push('\n');
                output.push_str(image_md);
                output.push('\n');
                inserted_images.insert((page, idx));
            }
        }
    }
}

/// Convert text lines to markdown, inserting tables and images at appropriate Y positions
pub(super) fn to_markdown_from_lines_with_tables_and_images(
    lines: Vec<TextLine>,
    options: MarkdownOptions,
    page_tables: std::collections::HashMap<u32, Vec<(f32, String)>>,
    page_images: std::collections::HashMap<u32, Vec<(f32, String)>>,
) -> String {
    if lines.is_empty() && page_tables.is_empty() && page_images.is_empty() {
        return String::new();
    }

    // Calculate font statistics
    let font_stats = calculate_font_stats(&lines);
    let base_size = options
        .base_font_size
        .unwrap_or(font_stats.most_common_size);

    // Merge drop caps with following text
    let lines = merge_drop_caps(lines, base_size);

    // Discover heading tiers for this document
    let heading_tiers = compute_heading_tiers(&lines, base_size);

    // Merge consecutive heading lines at the same level (e.g., wrapped titles)
    let lines = merge_heading_lines(lines, base_size, &heading_tiers);

    // Compute the typical line spacing for paragraph break detection.
    // For double-spaced documents (like legal/government PDFs), the normal
    // line spacing can be 2.3x base_size, which would exceed a fixed 1.8x
    // threshold and cause every line to be treated as a paragraph break.
    let para_threshold = compute_paragraph_threshold(&lines, base_size);

    let mut output = String::new();
    let mut current_page = 0u32;
    let mut prev_y = f32::MAX;
    let mut in_list = false;
    let mut in_paragraph = false;
    let mut last_list_x: Option<f32> = None;
    let mut prev_had_dot_leaders = false;
    let mut inserted_tables: HashSet<(u32, usize)> = HashSet::new();
    let mut inserted_images: HashSet<(u32, usize)> = HashSet::new();

    // Collect all pages that have tables or images (including image-only pages)
    let mut all_content_pages: Vec<u32> = page_tables
        .keys()
        .chain(page_images.keys())
        .copied()
        .collect();
    all_content_pages.sort();
    all_content_pages.dedup();

    for line in lines {
        // Page break
        if line.page != current_page {
            // Flush current page's remaining tables and images
            if current_page > 0 {
                flush_page_tables_and_images(
                    current_page,
                    &page_tables,
                    &page_images,
                    &mut inserted_tables,
                    &mut inserted_images,
                    &mut output,
                    &mut in_paragraph,
                );
                if in_paragraph {
                    output.push_str("\n\n");
                    in_paragraph = false;
                }
                output.push_str("\n\n");
            }

            // Flush any intermediate pages (image-only or table-only) between
            // current_page and line.page that have no text lines
            for &p in &all_content_pages {
                if p <= current_page {
                    continue;
                }
                if p >= line.page {
                    break;
                }
                flush_page_tables_and_images(
                    p,
                    &page_tables,
                    &page_images,
                    &mut inserted_tables,
                    &mut inserted_images,
                    &mut output,
                    &mut in_paragraph,
                );
                if in_paragraph {
                    output.push_str("\n\n");
                    in_paragraph = false;
                }
                output.push_str("\n\n");
            }

            current_page = line.page;
            prev_y = f32::MAX;

            if options.include_page_numbers {
                output.push_str(&format!("<!-- Page {} -->\n\n", current_page));
            }
        }

        // Check if we should insert a table before this line
        if let Some(tables) = page_tables.get(&current_page) {
            for (idx, (table_y, table_md)) in tables.iter().enumerate() {
                // Insert table when we pass its Y position
                if *table_y > line.y && !inserted_tables.contains(&(current_page, idx)) {
                    if in_paragraph {
                        output.push_str("\n\n");
                        in_paragraph = false;
                    }
                    output.push('\n');
                    output.push_str(table_md);
                    output.push('\n');
                    inserted_tables.insert((current_page, idx));
                }
            }
        }

        // Check if we should insert an image before this line
        if let Some(images) = page_images.get(&current_page) {
            for (idx, (image_y, image_md)) in images.iter().enumerate() {
                // Insert image when we pass its Y position
                if *image_y > line.y && !inserted_images.contains(&(current_page, idx)) {
                    if in_paragraph {
                        output.push_str("\n\n");
                        in_paragraph = false;
                    }
                    output.push('\n');
                    output.push_str(image_md);
                    output.push('\n');
                    inserted_images.insert((current_page, idx));
                }
            }
        }

        // Paragraph break: large forward Y gap (normal) or large backward jump
        // (newspaper columns emitted sequentially on the same page).
        let y_gap = prev_y - line.y;
        let is_para_break = y_gap.abs() > para_threshold;
        if is_para_break && in_paragraph {
            output.push_str("\n\n");
            in_paragraph = false;
        }
        // Don't immediately end list on paragraph break
        // Let the continuation check below decide if we're still in a list
        prev_y = line.y;

        // Get text with optional bold/italic formatting
        let text = line.text_with_formatting(options.detect_bold, options.detect_italic);
        let trimmed = text.trim();

        // Also get plain text for pattern matching (list detection, captions, etc.)
        let plain_text = line.text();
        let plain_trimmed = plain_text.trim();

        if trimmed.is_empty() {
            continue;
        }

        // Detect figure/table captions and source citations
        // These should be on their own line followed by a paragraph break
        if is_caption_line(plain_trimmed) {
            if in_paragraph {
                output.push_str("\n\n");
                in_paragraph = false;
            }
            output.push_str(trimmed);
            output.push_str("\n\n");
            continue;
        }

        // Detect headers by font size
        // Note: Headers typically shouldn't have bold markers since they're already emphasized
        // Skip very short text (drop caps/labels) and very long text (body paragraphs)
        if options.detect_headers
            && plain_trimmed.len() > 3
            && plain_trimmed.split_whitespace().count() <= 15
        {
            let line_font_size = line.items.first().map(|i| i.font_size).unwrap_or(base_size);
            if let Some(header_level) =
                detect_header_level(line_font_size, base_size, &heading_tiers)
            {
                if in_paragraph {
                    output.push_str("\n\n");
                    in_paragraph = false;
                }
                let prefix = "#".repeat(header_level);
                // Use plain text for headers to avoid redundant formatting
                output.push_str(&format!("{} {}\n\n", prefix, plain_trimmed));
                in_list = false;
                continue;
            }
        }

        // Detect list items
        if options.detect_lists && is_list_item(plain_trimmed) {
            if in_paragraph {
                output.push_str("\n\n");
                in_paragraph = false;
            }
            let formatted = format_list_item(trimmed);
            output.push_str(&formatted);
            output.push('\n');
            in_list = true;
            last_list_x = line.items.first().map(|i| i.x);
            continue;
        } else if in_list {
            // Check if this line is a continuation of the previous list item
            // Continuations have similar X position and reasonable Y gap
            let line_x = line.items.first().map(|i| i.x);
            let is_continuation = if let (Some(list_x), Some(curr_x)) = (last_list_x, line_x) {
                // Continuation criteria:
                // 1. X is at or past the list text position
                // 2. Y gap is not too large (max ~5 line heights)
                // 3. Not a new list item
                let x_ok = curr_x >= list_x - 5.0 && curr_x <= list_x + 50.0;
                let y_ok = y_gap < base_size * 7.0;
                x_ok && y_ok && !is_list_item(plain_trimmed) && !has_dot_leaders(plain_trimmed)
            } else {
                false
            };

            if is_continuation {
                // Append to previous list item with a space
                if output.ends_with('\n') {
                    output.pop();
                    output.push(' ');
                }
                output.push_str(trimmed);
                output.push('\n');
                continue;
            } else {
                in_list = false;
                last_list_x = None;
            }
        }

        // Detect code blocks by font
        if options.detect_code {
            let is_mono = line.items.iter().any(|i| is_monospace_font(&i.font));
            if is_mono {
                if in_paragraph {
                    output.push_str("\n\n");
                    in_paragraph = false;
                }
                // Use plain text for code blocks
                output.push_str(&format!("```\n{}\n```\n", plain_trimmed));
                continue;
            }
        }

        // Regular text - join lines within same paragraph with space
        let cur_dot_leaders = has_dot_leaders(plain_trimmed);
        if in_paragraph {
            if cur_dot_leaders || prev_had_dot_leaders {
                output.push('\n');
            } else {
                output.push(' ');
            }
        }
        output.push_str(trimmed);
        in_paragraph = true;
        prev_had_dot_leaders = cur_dot_leaders;
    }

    // Flush current page and any remaining pages with tables/images
    // (handles table-only pages after the last text line, and trailing image-only pages)
    flush_page_tables_and_images(
        current_page,
        &page_tables,
        &page_images,
        &mut inserted_tables,
        &mut inserted_images,
        &mut output,
        &mut in_paragraph,
    );
    for &p in &all_content_pages {
        if p <= current_page {
            continue;
        }
        flush_page_tables_and_images(
            p,
            &page_tables,
            &page_images,
            &mut inserted_tables,
            &mut inserted_images,
            &mut output,
            &mut in_paragraph,
        );
    }

    // Close final paragraph
    if in_paragraph {
        output.push('\n');
    }

    // Clean up and post-process
    clean_markdown(output, &options)
}

/// Convert text lines to markdown
pub fn to_markdown_from_lines(lines: Vec<TextLine>, options: MarkdownOptions) -> String {
    if lines.is_empty() {
        return String::new();
    }

    // Calculate font statistics
    let font_stats = calculate_font_stats(&lines);
    let base_size = options
        .base_font_size
        .unwrap_or(font_stats.most_common_size);

    // Merge drop caps with following text
    let lines = merge_drop_caps(lines, base_size);

    // Discover heading tiers for this document
    let heading_tiers = compute_heading_tiers(&lines, base_size);

    // Merge consecutive heading lines at the same level (e.g., wrapped titles)
    let lines = merge_heading_lines(lines, base_size, &heading_tiers);

    // Compute the typical line spacing for paragraph break detection
    let para_threshold = compute_paragraph_threshold(&lines, base_size);

    let mut output = String::new();
    let mut current_page = 0u32;
    let mut prev_y = f32::MAX;
    let mut in_list = false;
    let mut in_paragraph = false;
    let mut last_list_x: Option<f32> = None;
    let mut prev_had_dot_leaders = false;

    for line in lines {
        // Page break
        if line.page != current_page {
            if current_page > 0 {
                if in_paragraph {
                    output.push_str("\n\n");
                    in_paragraph = false;
                }
                output.push_str("\n\n");
            }
            current_page = line.page;
            prev_y = f32::MAX;
            in_list = false;
            last_list_x = None;
            prev_had_dot_leaders = false;

            if options.include_page_numbers {
                output.push_str(&format!("<!-- Page {} -->\n\n", current_page));
            }
        }

        // Paragraph break: large forward Y gap (normal) or large backward jump
        // (newspaper columns emitted sequentially on the same page).
        let y_gap = prev_y - line.y;
        let is_para_break = y_gap.abs() > para_threshold;
        if is_para_break && in_paragraph {
            output.push_str("\n\n");
            in_paragraph = false;
        }
        // Don't immediately end list on paragraph break
        // Let the continuation check below decide if we're still in a list
        prev_y = line.y;

        // Get text with optional bold/italic formatting
        let text = line.text_with_formatting(options.detect_bold, options.detect_italic);
        let trimmed = text.trim();

        // Also get plain text for pattern matching
        let plain_text = line.text();
        let plain_trimmed = plain_text.trim();

        if trimmed.is_empty() {
            continue;
        }

        // Detect figure/table captions and source citations
        // These should be on their own line followed by a paragraph break
        if is_caption_line(plain_trimmed) {
            if in_paragraph {
                output.push_str("\n\n");
                in_paragraph = false;
            }
            output.push_str(trimmed);
            output.push_str("\n\n");
            continue;
        }

        // Detect headers by font size
        // Skip very short text (drop caps/labels) and very long text (body paragraphs)
        if options.detect_headers
            && plain_trimmed.len() > 3
            && plain_trimmed.split_whitespace().count() <= 15
        {
            let line_font_size = line.items.first().map(|i| i.font_size).unwrap_or(base_size);
            if let Some(header_level) =
                detect_header_level(line_font_size, base_size, &heading_tiers)
            {
                if in_paragraph {
                    output.push_str("\n\n");
                    in_paragraph = false;
                }
                let prefix = "#".repeat(header_level);
                // Use plain text for headers to avoid redundant formatting
                output.push_str(&format!("{} {}\n\n", prefix, plain_trimmed));
                in_list = false;
                continue;
            }
        }

        // Detect list items
        if options.detect_lists && is_list_item(plain_trimmed) {
            if in_paragraph {
                output.push_str("\n\n");
                in_paragraph = false;
            }
            let formatted = format_list_item(trimmed);
            output.push_str(&formatted);
            output.push('\n');
            in_list = true;
            last_list_x = line.items.first().map(|i| i.x);
            continue;
        } else if in_list {
            // Check if this line is a continuation of the previous list item
            let line_x = line.items.first().map(|i| i.x);
            let is_continuation = if let (Some(list_x), Some(curr_x)) = (last_list_x, line_x) {
                // Continuation criteria:
                // 1. X is at or past the list text position
                // 2. Y gap is not too large (max ~5 line heights)
                // 3. Not a new list item
                let x_ok = curr_x >= list_x - 5.0 && curr_x <= list_x + 50.0;
                let y_ok = y_gap < base_size * 7.0;
                x_ok && y_ok && !is_list_item(plain_trimmed) && !has_dot_leaders(plain_trimmed)
            } else {
                false
            };

            if is_continuation {
                // Append to previous list item with a space
                if output.ends_with('\n') {
                    output.pop();
                    output.push(' ');
                }
                output.push_str(trimmed);
                output.push('\n');
                continue;
            } else {
                in_list = false;
                last_list_x = None;
            }
        }

        // Detect code blocks by font
        if options.detect_code {
            let is_mono = line.items.iter().any(|i| is_monospace_font(&i.font));
            if is_mono {
                if in_paragraph {
                    output.push_str("\n\n");
                    in_paragraph = false;
                }
                // Use plain text for code blocks
                output.push_str(&format!("```\n{}\n```\n", plain_trimmed));
                continue;
            }
        }

        // Regular text - join lines within same paragraph with space
        let cur_dot_leaders = has_dot_leaders(plain_trimmed);
        if in_paragraph {
            if cur_dot_leaders || prev_had_dot_leaders {
                output.push('\n');
            } else {
                output.push(' ');
            }
        }
        output.push_str(trimmed);
        in_paragraph = true;
        prev_had_dot_leaders = cur_dot_leaders;
    }

    // Close final paragraph
    if in_paragraph {
        output.push('\n');
    }

    // Clean up and post-process
    clean_markdown(output, &options)
}
