diff --git a/src/corpus.rs b/src/corpus.rs
index 4b0fd9d..5dd59ea 100644
--- a/src/corpus.rs
+++ b/src/corpus.rs
@@ -1 +1,43 @@
-// implemented in a later task
+use crate::model::{AlphaIdEntry, AppError};
+
+/// Normalize an ICD code field by removing classification marks.
+pub fn normalize_code(raw: &str) -> String {
+    raw.trim().trim_end_matches(['+', '*', '!']).trim().to_string()
+}
+
+pub fn parse_line(line: &str) -> Option<AlphaIdEntry> {
+    let f: Vec<&str> = line.split('|').collect();
+    if f.len() < 8 { return None; }
+    Some(AlphaIdEntry {
+        valid: f[0].trim() == "1",
+        alpha_id: f[1].trim().to_string(),
+        icd_primary: normalize_code(f[2]),
+        icd_star: normalize_code(f[3]),
+        icd_addon: normalize_code(f[4]),
+        icd_primary2: normalize_code(f[5]),
+        orpha: f[6].trim().to_string(),
+        text: f[7].trim().to_string(),
+    })
+}
+
+pub fn load(path: &str) -> Result<Vec<AlphaIdEntry>, AppError> {
+    let raw = std::fs::read_to_string(path)
+        .map_err(|e| AppError::Io(format!("{path}: {e}")))?;
+    let entries: Vec<AlphaIdEntry> = raw
+        .lines()
+        .filter(|l| !l.trim().is_empty())
+        .filter_map(parse_line)
+        .collect();
+    if entries.is_empty() {
+        return Err(AppError::Parse(format!("no entries parsed from {path}")));
+    }
+    Ok(entries)
+}
+
+/// The primary ICD code a matched entry contributes (falls back to star/addon).
+pub fn primary_code(e: &AlphaIdEntry) -> Option<&str> {
+    for c in [&e.icd_primary, &e.icd_primary2, &e.icd_star, &e.icd_addon] {
+        if !c.is_empty() { return Some(c); }
+    }
+    None
+}
diff --git a/tests/corpus_tests.rs b/tests/corpus_tests.rs
new file mode 100644
index 0000000..a47dfe3
--- /dev/null
+++ b/tests/corpus_tests.rs
@@ -0,0 +1,29 @@
+use alpha_id::corpus;
+
+#[test]
+fn parses_pipe_line_into_entry() {
+    let line = "1|I69812|A01.0+|I39.8*|||99745|Typhus-Endokarditis";
+    let e = corpus::parse_line(line).expect("should parse");
+    assert_eq!(e.alpha_id, "I69812");
+    assert!(e.valid);
+    assert_eq!(e.icd_primary, "A01.0"); // normalized: no '+'
+    assert_eq!(e.icd_star, "I39.8");    // normalized: no '*'
+    assert_eq!(e.orpha, "99745");
+    assert_eq!(e.text, "Typhus-Endokarditis");
+}
+
+#[test]
+fn invalid_flag_is_false() {
+    let line = "0|I97837|||U81!|||Bakterien mit Multiresistenz";
+    let e = corpus::parse_line(line).unwrap();
+    assert!(!e.valid);
+    assert_eq!(e.icd_addon, "U81"); // field 5, '!' stripped
+    assert_eq!(e.icd_primary, "");
+}
+
+#[test]
+fn loads_full_real_corpus() {
+    let entries = corpus::load("data/icd10gm2026_alphaidse_edvtxt_20250926.txt").unwrap();
+    assert_eq!(entries.len(), 90_898);
+    assert!(entries.iter().any(|e| e.text.contains("Diabetes mellitus Typ 2")));
+}