From 776389af49adf195042d455b9d76213942fecf20 Mon Sep 17 00:00:00 2001
From: Gabriel Kaszewski <gabrielkaszewski@gmail.com>
Date: Wed, 8 Apr 2026 01:47:17 +0200
Subject: [PATCH] feat(ug-parser): parse sections, lyrics, and chord positions
 from UG HTML

---
 crates/infrastructure/ug-parser/src/parser.rs | 143 +++++++++++++++++-
 1 file changed, 140 insertions(+), 3 deletions(-)

diff --git a/crates/infrastructure/ug-parser/src/parser.rs b/crates/infrastructure/ug-parser/src/parser.rs
index 749eda5..8f0c2d9 100644
--- a/crates/infrastructure/ug-parser/src/parser.rs
+++ b/crates/infrastructure/ug-parser/src/parser.rs
@@ -1,4 +1,3 @@
-#[allow(unused_imports)]
 use domain::{
     Chord, ChordPosition, LyricLine, ParseError, Section, SectionKind, Song, SongMeta,
     TabParserPort,
@@ -77,8 +76,117 @@ impl UgHtmlParser {
         })
     }
 
-    fn parse_sections(_document: &Html) -> Result<Vec<Section>, ParseError> {
-        Ok(vec![])
+    fn parse_sections(document: &Html) -> Result<Vec<Section>, ParseError> {
+        let pre_sel = Selector::parse("pre").unwrap();
+        let pre = document
+            .select(&pre_sel)
+            .next()
+            .ok_or(ParseError::MissingContent)?;
+
+        let inner_html = pre.inner_html();
+        let raw_lines: Vec<&str> = inner_html.split('\n').collect();
+
+        let mut sections: Vec<Section> = Vec::new();
+        let mut current_section: Option<Section> = None;
+        let mut pending_chords: Vec<ChordPosition> = Vec::new();
+
+        for raw_line in &raw_lines {
+            let text_only = Self::strip_html(raw_line);
+            let trimmed = text_only.trim();
+
+            // Section header: "[Chorus]", "[Verse 1]", etc.
+            if let Some(label) = Self::extract_section_label(trimmed) {
+                if let Some(sec) = current_section.take() {
+                    sections.push(sec);
+                }
+                current_section = Some(Section {
+                    kind: SectionKind::from_label(&label),
+                    label: Some(label),
+                    lines: Vec::new(),
+                });
+                pending_chords.clear();
+                continue;
+            }
+
+            // Blank line — flush pending chords if any (chord line with no following lyric)
+            if trimmed.is_empty() {
+                if !pending_chords.is_empty() {
+                    if let Some(sec) = current_section.as_mut() {
+                        sec.lines.push(LyricLine {
+                            text: String::new(),
+                            chords: pending_chords.drain(..).collect(),
+                        });
+                    }
+                }
+                continue;
+            }
+
+            // Chord line: contains span elements
+            if raw_line.contains("<span") {
+                pending_chords = Self::parse_chord_line(raw_line);
+                continue;
+            }
+
+            // Lyric line
+            if let Some(sec) = current_section.as_mut() {
+                sec.lines.push(LyricLine {
+                    text: trimmed.to_string(),
+                    chords: pending_chords.drain(..).collect(),
+                });
+            }
+        }
+
+        if let Some(sec) = current_section {
+            sections.push(sec);
+        }
+
+        Ok(sections)
+    }
+
+    /// Strip all HTML tags, returning plain text.
+    fn strip_html(s: &str) -> String {
+        let frag = Html::parse_fragment(s);
+        frag.root_element().text().collect()
+    }
+
+    /// If `s` matches `[Label]`, return `Label`. Else None.
+    fn extract_section_label(s: &str) -> Option<String> {
+        let s = s.trim();
+        if s.starts_with('[') && s.ends_with(']') && s.len() > 2 {
+            Some(s[1..s.len() - 1].to_string())
+        } else {
+            None
+        }
+    }
+
+    /// Parse a chord line (raw HTML) into chord positions.
+    /// Walks text nodes and span[data-name] elements in order to compute offsets.
+    fn parse_chord_line(line_html: &str) -> Vec<ChordPosition> {
+        let frag = Html::parse_fragment(line_html);
+        let root = frag.root_element();
+        let mut chords = Vec::new();
+        let mut offset = 0usize;
+
+        for child in root.children() {
+            use scraper::node::Node;
+            match child.value() {
+                Node::Text(text) => {
+                    offset += text.chars().count();
+                }
+                Node::Element(el) => {
+                    if el.name() == "span" {
+                        if let Some(chord_name) = el.attr("data-name") {
+                            if let Some(chord) = Chord::parse(chord_name) {
+                                chords.push(ChordPosition { offset, chord });
+                                offset += chord_name.chars().count();
+                            }
+                        }
+                    }
+                }
+                _ => {}
+            }
+        }
+        chords
     }
 }
 
@@ -124,4 +232,33 @@ mod tests {
         let song = parser.parse(&html).unwrap();
         assert_eq!(song.meta.capo, None);
     }
+
+    #[test]
+    fn parses_sections() {
+        let parser = UgHtmlParser;
+        let html = sample_html("A DROP IN THE OCEAN.html");
+        let song = parser.parse(&html).unwrap();
+        assert!(
+            song.sections.len() >= 3,
+            "expected >=3 sections, got {}",
+            song.sections.len()
+        );
+        assert_eq!(song.sections[0].kind, domain::SectionKind::Chorus);
+    }
+
+    #[test]
+    fn parses_chord_positions() {
+        let parser = UgHtmlParser;
+        let html = sample_html("A DROP IN THE OCEAN.html");
+        let song = parser.parse(&html).unwrap();
+        // First section, first line: "A drop in the ocean,"
+        // Chord "Em" should be at offset 0 (or small offset from leading whitespace)
+        let first_line = &song.sections[0].lines[0];
+        assert_eq!(first_line.text, "A drop in the ocean,");
+        assert!(
+            first_line.chords[0].chord.name(true) == "Em",
+            "expected Em chord, got {}",
+            first_line.chords[0].chord.name(true)
+        );
+    }
 }