model/project: add Project::merged for pure combining

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: Idf955432e57d87352dffa961e145fcb76a6a6964

src/model/project.rs

@@ -3,6 +3,7 @@ use std::collections::{HashMap, HashSet};
 use serde::{Deserialize, Serialize};
 
 use super::enums::{ProjectSide, ProjectType, ReleaseType, UpdateStrategy};
+use crate::error::{PakkerError, Result};
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Project {
@@ -169,6 +170,80 @@ impl Project {
     self.aliases.extend(other.aliases);
   }
 
+  /// Merge this project with another, returning a new combined project.
+  /// Like Pakku's `Project.plus()`, this is a pure operation that doesn't
+  /// modify either project.
+  ///
+  /// # Errors
+  /// Returns `PakkerError::InvalidProject` if the projects have different types
+  /// or conflicting pakku_links.
+  pub fn merged(&self, other: Self) -> Result<Self> {
+    if self.r#type != other.r#type {
+      return Err(PakkerError::InvalidProject(format!(
+        "Cannot merge projects of different types: {:?} vs {:?}",
+        self.r#type, other.r#type
+      )));
+    }
+
+    if !other.pakku_links.is_empty() && self.pakku_links != other.pakku_links {
+      return Err(PakkerError::InvalidProject(
+        "Cannot merge projects with conflicting pakku_links".to_string(),
+      ));
+    }
+
+    // Prefer non-default side
+    let side = if self.side != ProjectSide::Both {
+      self.side
+    } else {
+      other.side
+    };
+
+    let mut id = self.id.clone();
+    for (platform, other_id) in other.id {
+      id.entry(platform).or_insert(other_id);
+    }
+
+    let mut slug = self.slug.clone();
+    for (platform, other_slug) in other.slug {
+      slug.entry(platform).or_insert(other_slug);
+    }
+
+    let mut name = self.name.clone();
+    for (platform, other_name) in other.name {
+      name.entry(platform).or_insert(other_name);
+    }
+
+    let mut files = self.files.clone();
+    for file in other.files {
+      if !files.iter().any(|f| f.id == file.id) {
+        files.push(file);
+      }
+    }
+
+    let mut aliases = self.aliases.clone();
+    aliases.extend(other.aliases);
+
+    Ok(Self {
+      pakku_id: self.pakku_id.clone(),
+      pakku_links: self.pakku_links.clone(),
+      r#type: self.r#type,
+      side,
+      slug,
+      name,
+      id,
+      update_strategy: self.update_strategy,
+      redistributable: self.redistributable && other.redistributable,
+      subpath: self.subpath.clone().or(other.subpath.clone()),
+      aliases,
+      export: if self.export {
+        self.export
+      } else {
+        other.export
+      },
+      files,
+    })
+  }
+
   /// Check if versions match across all providers.
   /// Returns true if all provider files have the same version/file,
   /// or if there's only one provider.
@@ -760,4 +835,112 @@ mod tests {
     let url = file.get_site_url(&project);
     assert!(url.is_none());
   }
+
+  #[test]
+  fn test_merged_different_types_returns_error() {
+    let mut p1 =
+      Project::new("id1".to_string(), ProjectType::Mod, ProjectSide::Both);
+    p1.name.insert("modrinth".to_string(), "Mod1".to_string());
+
+    let mut p2 = Project::new(
+      "id2".to_string(),
+      ProjectType::ResourcePack,
+      ProjectSide::Both,
+    );
+    p2.name.insert("modrinth".to_string(), "RP1".to_string());
+
+    assert!(p1.merged(p2).is_err());
+  }
+
+  #[test]
+  fn test_merged_combines_ids_and_slugs() {
+    let mut p1 =
+      Project::new("id1".to_string(), ProjectType::Mod, ProjectSide::Both);
+    p1.add_platform(
+      "modrinth".to_string(),
+      "mr1".to_string(),
+      "mod1".to_string(),
+      "Mod 1".to_string(),
+    );
+
+    let mut p2 =
+      Project::new("id2".to_string(), ProjectType::Mod, ProjectSide::Both);
+    p2.add_platform(
+      "curseforge".to_string(),
+      "cf1".to_string(),
+      "mod1".to_string(),
+      "Mod 1".to_string(),
+    );
+
+    let merged = p1.merged(p2).unwrap();
+    assert_eq!(merged.id.get("modrinth"), Some(&"mr1".to_string()));
+    assert_eq!(merged.id.get("curseforge"), Some(&"cf1".to_string()));
+    assert_eq!(merged.slug.get("modrinth"), Some(&"mod1".to_string()));
+    assert_eq!(merged.slug.get("curseforge"), Some(&"mod1".to_string()));
+  }
+
+  #[test]
+  fn test_merged_prefers_non_both_side() {
+    let p1 =
+      Project::new("id1".to_string(), ProjectType::Mod, ProjectSide::Client);
+    let p2 =
+      Project::new("id2".to_string(), ProjectType::Mod, ProjectSide::Both);
+
+    let merged = p1.merged(p2.clone()).unwrap();
+    assert_eq!(merged.side, ProjectSide::Client);
+
+    let merged2 = p2.merged(p1).unwrap();
+    assert_eq!(merged2.side, ProjectSide::Client);
+  }
+
+  #[test]
+  fn test_merged_preserves_pakku_id() {
+    let p1 =
+      Project::new("id1".to_string(), ProjectType::Mod, ProjectSide::Both);
+    let p2 =
+      Project::new("id2".to_string(), ProjectType::Mod, ProjectSide::Both);
+
+    let merged = p1.merged(p2).unwrap();
+    assert_eq!(merged.pakku_id, Some("id1".to_string()));
+  }
+
+  #[test]
+  fn test_merged_deduplicates_files() {
+    let mut p1 =
+      Project::new("id1".to_string(), ProjectType::Mod, ProjectSide::Both);
+    p1.files.push(ProjectFile {
+      file_type:             "modrinth".to_string(),
+      file_name:             "mod-1.0.0.jar".to_string(),
+      mc_versions:           vec!["1.20.1".to_string()],
+      loaders:               vec!["fabric".to_string()],
+      release_type:          ReleaseType::Release,
+      url:                   "https://example.com/mod.jar".to_string(),
+      id:                    "file1".to_string(),
+      parent_id:             "mod123".to_string(),
+      hashes:                HashMap::new(),
+      required_dependencies: vec![],
+      size:                  1024,
+      date_published:        "2024-01-01T00:00:00Z".to_string(),
+    });
+
+    let mut p2 =
+      Project::new("id2".to_string(), ProjectType::Mod, ProjectSide::Both);
+    p2.files.push(ProjectFile {
+      file_type:             "modrinth".to_string(),
+      file_name:             "mod-1.0.0.jar".to_string(),
+      mc_versions:           vec!["1.20.1".to_string()],
+      loaders:               vec!["fabric".to_string()],
+      release_type:          ReleaseType::Release,
+      url:                   "https://example.com/mod.jar".to_string(),
+      id:                    "file1".to_string(),
+      parent_id:             "mod123".to_string(),
+      hashes:                HashMap::new(),
+      required_dependencies: vec![],
+      size:                  1024,
+      date_published:        "2024-01-01T00:00:00Z".to_string(),
+    });
+
+    let merged = p1.merged(p2).unwrap();
+    assert_eq!(merged.files.len(), 1);
+  }
 }