feat: add classification prompt and schema for article categorization

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/services/llm/schema.rs

@@ -82,6 +82,31 @@ pub fn build_category_schema(categories: &[String], max_items_per_category: i32)
     })
 }
 
+/// Build a JSON Schema for the article classification response.
+///
+/// The LLM returns an array of assignments mapping article indices to category names.
+pub fn build_classification_schema() -> Value {
+    serde_json::json!({
+        "type": "object",
+        "properties": {
+            "assignments": {
+                "type": "array",
+                "items": {
+                    "type": "object",
+                    "properties": {
+                        "index": { "type": "integer", "description": "Article index from the input list" },
+                        "category": { "type": "string", "description": "Category name to assign this article to" }
+                    },
+                    "required": ["index", "category"],
+                    "additionalProperties": false
+                }
+            }
+        },
+        "required": ["assignments"],
+        "additionalProperties": false
+    })
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -261,4 +286,17 @@ mod tests {
         assert_eq!(props["category_0"]["description"], "AI & Machine Learning");
         assert_eq!(props["category_1"]["description"], "R&D / Innovation");
     }
+
+    #[test]
+    fn classification_schema_has_assignments_array() {
+        let schema = build_classification_schema();
+        assert_eq!(schema["type"], "object");
+        let assignments = &schema["properties"]["assignments"];
+        assert_eq!(assignments["type"], "array");
+        let item_props = &assignments["items"]["properties"];
+        assert!(item_props.get("index").is_some());
+        assert!(item_props.get("category").is_some());
+        assert_eq!(assignments["items"]["additionalProperties"], false);
+        assert_eq!(schema["additionalProperties"], false);
+    }
 }

backend/src/services/prompts.rs

@@ -140,6 +140,64 @@ pub fn build_rewrite_prompt(
     (system_prompt, user_prompt)
 }
 
+/// Build a prompt for classifying scraped articles into categories.
+///
+/// # Arguments
+/// * `articles` — scraped articles to classify (title + body snippet used)
+/// * `categories` — user categories + "Autre"
+/// * `max_per_category` — max items allowed per category
+/// * `filled_counts` — how many items already fill each category (for Phase 2)
+pub fn build_classification_prompt(
+    articles: &[ScrapedNewsItem],
+    categories: &[String],
+    max_per_category: i32,
+    filled_counts: &std::collections::HashMap<String, usize>,
+) -> (String, String) {
+    let system_prompt =
+        "Tu es un assistant qui classe des articles dans des categories. \
+         Reponds uniquement au format JSON demande."
+            .to_string();
+
+    let articles_json: Vec<serde_json::Value> = articles
+        .iter()
+        .enumerate()
+        .map(|(i, a)| {
+            let snippet: String = a.scraped_content.chars().take(500).collect();
+            serde_json::json!({
+                "index": i,
+                "title": a.title,
+                "url": a.url,
+                "snippet": snippet
+            })
+        })
+        .collect();
+
+    let categories_info: Vec<String> = categories
+        .iter()
+        .map(|cat| {
+            let filled = filled_counts.get(cat).copied().unwrap_or(0);
+            let remaining = (max_per_category as usize).saturating_sub(filled);
+            if remaining == 1 {
+                format!("- \"{}\" (encore 1 place)", cat)
+            } else {
+                format!("- \"{}\" (encore {} places)", cat, remaining)
+            }
+        })
+        .collect();
+
+    let user_prompt = format!(
+        "Voici une liste d'articles :\n{articles}\n\n\
+         Categories disponibles :\n{categories}\n\n\
+         Classe chaque article dans la categorie la plus appropriee. \
+         Si un article ne correspond a aucune categorie, classe-le dans \"Autre\".\n\
+         Respecte le nombre de places restantes par categorie.",
+        articles = serde_json::to_string_pretty(&articles_json).unwrap_or_default(),
+        categories = categories_info.join("\n"),
+    );
+
+    (system_prompt, user_prompt)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -317,4 +375,49 @@ mod tests {
         let (_, user_prompt) = build_search_prompt(&settings, &sources, date, &[]);
         assert!(!user_prompt.contains("Evite si possible"));
     }
+
+    #[test]
+    fn classification_prompt_includes_categories_and_articles() {
+        let articles = vec![
+            ScrapedNewsItem {
+                title: "GPT-5 Released".into(),
+                url: "https://openai.com/blog/gpt5".into(),
+                summary: "s".into(),
+                original_title: "t".into(),
+                scraped_content: "OpenAI released GPT-5 today with major improvements".into(),
+            },
+        ];
+        let categories = vec!["AI News".to_string(), "Autre".to_string()];
+        let filled = std::collections::HashMap::new();
+        let (_, user_prompt) = build_classification_prompt(&articles, &categories, 4, &filled);
+        assert!(user_prompt.contains("GPT-5 Released"));
+        assert!(user_prompt.contains("AI News"));
+        assert!(user_prompt.contains("Autre"));
+        assert!(user_prompt.contains("encore 4 places"));
+    }
+
+    #[test]
+    fn classification_prompt_shows_reduced_capacity() {
+        let articles = vec![
+            ScrapedNewsItem {
+                title: "T".into(), url: "https://a.com/1".into(),
+                summary: "s".into(), original_title: "t".into(),
+                scraped_content: "Content".into(),
+            },
+        ];
+        let categories = vec!["AI News".to_string(), "Autre".to_string()];
+        let mut filled = std::collections::HashMap::new();
+        filled.insert("AI News".to_string(), 3);
+        let (_, user_prompt) = build_classification_prompt(&articles, &categories, 4, &filled);
+        assert!(user_prompt.contains("encore 1 place"));
+    }
+
+    #[test]
+    fn classification_prompt_system_is_french() {
+        let articles = vec![];
+        let categories = vec!["Autre".to_string()];
+        let filled = std::collections::HashMap::new();
+        let (system, _) = build_classification_prompt(&articles, &categories, 4, &filled);
+        assert!(system.contains("classe"));
+    }
 }