using Invercargill;
using Invercargill.DataStructures;
using Invercargill.Expressions;
using InvercargillSql.Orm;
using Inversion;
using ClankerSaddle.Data;

namespace ClankerSaddle.Services {

    /** Valid values of {@link ProjectLink.relationship}. */
    public const string LINK_CO_DEVELOPED = "co-developed";
    public const string LINK_REFERENCE = "reference";

    /**
     * Project storage: CRUD over `projects`, the directed
     * co-developed/reference link graph in `project_links`, and the
     * project's LLM-authored notes.
     */
    public class ProjectService : Object {

        private OrmSession db = inject<OrmSession>();

        /** Inserts a project; `summary` may be empty. */
        public async Project create_project(string name, string git_url,
                string default_branch, string? summary) throws Error {
            var project = new Project() {
                name = name,
                git_url = git_url,
                default_branch = default_branch.length > 0 ? default_branch : "main",
                summary = summary != null && summary.length > 0 ? summary : null,
                created_at = new DateTime.now_local()
            };
            yield db.insert_async<Project>(project);
            return project;
        }

        /** Loads the project identified by `id`, or null. */
        public async Project? get_project(int64 id) throws Error {
            return yield db.query<Project>()
                .where(expr("id == $0", elem<int64?>(id)))
                .first_async();
        }

        /** Lists every project ordered by name. */
        public async ImmutableLot<Project> list_projects() throws Error {
            return yield db.query<Project>()
                .order_by(expr("name"))
                .materialise_async();
        }

        /**
         * Saves the editable fields of the project identified by `id`;
         * empty arguments keep their current values. Returns the saved
         * project, or null when no such project exists.
         */
        public async Project? update_project(int64 id, string? name, string? git_url,
                string? default_branch, string? summary) throws Error {
            var project = yield get_project(id);
            if (project == null) {
                return null;
            }
            if (name != null && name.length > 0) {
                project.name = name;
            }
            if (git_url != null && git_url.length > 0) {
                project.git_url = git_url;
            }
            if (default_branch != null && default_branch.length > 0) {
                project.default_branch = default_branch;
            }
            if (summary != null) {
                project.summary = summary.length > 0 ? summary : null;
            }
            yield db.update_async<Project>(project);
            return project;
        }

        /**
         * Links `linked_id` to `parent_id` with `relationship`
         * ('co-developed' or 'reference'); self-links and duplicates are
         * rejected.
         */
        public async ProjectLink add_link(int64 parent_id, int64 linked_id,
                string relationship) throws Error {
            if (relationship != LINK_CO_DEVELOPED && relationship != LINK_REFERENCE) {
                throw new Error(Quark.from_string("clanker-saddle"), 1,
                    @"Relationship must be '$(LINK_CO_DEVELOPED)' or '$(LINK_REFERENCE)'");
            }
            if (parent_id == linked_id) {
                throw new Error(Quark.from_string("clanker-saddle"), 2,
                    "A project cannot be linked to itself");
            }
            var parent = yield get_project(parent_id);
            var linked = yield get_project(linked_id);
            if (parent == null || linked == null) {
                throw new Error(Quark.from_string("clanker-saddle"), 3,
                    "Both projects must exist");
            }
            var existing = yield db.query<ProjectLink>()
                .where(expr("parent_project_id == $0 && linked_project_id == $1",
                    elem<int64?>(parent_id), elem<int64?>(linked_id)))
                .materialise_async();
            if (existing.length > 0) {
                throw new Error(Quark.from_string("clanker-saddle"), 4,
                    "Those projects are already linked");
            }

            var link = new ProjectLink() {
                parent_project_id = parent_id,
                linked_project_id = linked_id,
                relationship = relationship
            };
            yield db.insert_async<ProjectLink>(link);
            return link;
        }

        /** Deletes the link identified by `id`. */
        public async void remove_link(int64 id) throws Error {
            var link = yield db.query<ProjectLink>()
                .where(expr("id == $0", elem<int64?>(id)))
                .first_async();
            if (link != null) {
                yield db.delete_async<ProjectLink>((!)link);
            }
        }

        /** Lists every link whose parent is `project_id`. */
        public async ImmutableLot<ProjectLink> list_links(int64 project_id) throws Error {
            return yield db.query<ProjectLink>()
                .where(expr("parent_project_id == $0", elem<int64?>(project_id)))
                .materialise_async();
        }

        /** Loads the project identified by `name`, or null. */
        public async Project? get_project_by_name(string name) throws Error {
            return yield db.query<Project>()
                .where(expr("name == $0", elem(name)))
                .first_async();
        }

        /**
         * Inserts a project note (LLM-authored via the callback endpoint).
         * `source_task_id` may be 0 (unknown source task).
         */
        public async ProjectNote add_note(int64 project_id, int64 source_task_id,
                string body) throws Error {
            var note = new ProjectNote() {
                project_id = project_id,
                source_task_id = source_task_id,
                body = body,
                created_at = new DateTime.now_local()
            };
            yield db.insert_async<ProjectNote>(note);
            return note;
        }

        /** Loads the note identified by `id`, or null. */
        public async ProjectNote? get_note(int64 id) throws Error {
            return yield db.query<ProjectNote>()
                .where(expr("id == $0", elem<int64?>(id)))
                .first_async();
        }

        /** A project's notes, oldest first. */
        public async ImmutableLot<ProjectNote> list_notes(int64 project_id) throws Error {
            return yield db.query<ProjectNote>()
                .where(expr("project_id == $0", elem<int64?>(project_id)))
                .order_by(expr("id"))
                .materialise_async();
        }

        /** Deletes the note identified by `id`. */
        public async void delete_note(int64 id) throws Error {
            var note = yield get_note(id);
            if (note != null) {
                yield db.delete_async<ProjectNote>((!)note);
            }
        }
    }
}