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

namespace ClankerSaddle.Services {

    /**
     * Rule storage: CRUD over `rules` plus their project and task
     * attachments, and the effective-rule computation the dispatcher
     * ships in the `/start` payload.
     */
    public class RuleService : Object {

        private OrmSession db = inject<OrmSession>();

        /**
         * Inserts a rule; names are unique. Returns the stored row (with
         * its id).
         */
        public async Rule create_rule(string name, string body) throws Error {
            if (name.strip().length == 0) {
                throw new Error(Quark.from_string("clanker-saddle"), 30,
                    "A rule name is required");
            }
            if (body.strip().length == 0) {
                throw new Error(Quark.from_string("clanker-saddle"), 31,
                    "A rule body is required");
            }
            var existing = yield db.query<Rule>()
                .where(expr("name == $0", elem(name.strip())))
                .first_async();
            if (existing != null) {
                throw new Error(Quark.from_string("clanker-saddle"), 32,
                    @"A rule named '$(name)' already exists");
            }
            var rule = new Rule() {
                name = name.strip(),
                body = body,
                created_at = new DateTime.now_local()
            };
            yield db.insert_async<Rule>(rule);
            return rule;
        }

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

        /** Every rule ordered by name. */
        public async ImmutableLot<Rule> list_rules() throws Error {
            return yield db.query<Rule>()
                .order_by(expr("name"))
                .materialise_async();
        }

        /**
         * Saves the editable fields of the rule identified by `id`; null
         * or empty arguments keep their current values. An edit stamps
         * `updated_at` — the resume-time context_update delta keys on
         * it, so a rule edited while a workspace was parked reaches
         * the agent as a turn. Returns null when the rule does not
         * exist.
         */
        public async Rule? update_rule(int64 id, string? name, string? body) throws Error {
            var rule = yield get_rule(id);
            if (rule == null) {
                return null;
            }
            bool edited = false;
            if (name != null && name.strip().length > 0) {
                var clash = yield db.query<Rule>()
                    .where(expr("name == $0 && id != $1", elem(name.strip()), elem<int64?>(id)))
                    .first_async();
                if (clash != null) {
                    throw new Error(Quark.from_string("clanker-saddle"), 32,
                        @"A rule named '$(name)' already exists");
                }
                if (((!)rule).name != name.strip()) {
                    ((!)rule).name = name.strip();
                    edited = true;
                }
            }
            if (body != null && body.length > 0) {
                if (((!)rule).body != body) {
                    ((!)rule).body = body;
                    edited = true;
                }
            }
            if (edited) {
                ((!)rule).updated_at = new DateTime.now_local();
            }
            yield db.update_async<Rule>((!)rule);
            return rule;
        }

        /**
         * Deletes a rule and every attachment referencing it (task and
         * project links go with it).
         */
        public async void delete_rule(int64 id) throws Error {
            foreach (var link in yield db.query<TaskRule>()
                    .where(expr("rule_id == $0", elem<int64?>(id)))
                    .materialise_async()) {
                yield db.delete_async<TaskRule>(link);
            }
            foreach (var link in yield db.query<RuleProject>()
                    .where(expr("rule_id == $0", elem<int64?>(id)))
                    .materialise_async()) {
                yield db.delete_async<RuleProject>(link);
            }
            var rule = yield get_rule(id);
            if (rule != null) {
                yield db.delete_async<Rule>((!)rule);
            }
        }

        /**
         * Attaches `rule_id` to `project_id`; duplicates are rejected
         * (the pair is unique).
         */
        public async void attach_rule_to_project(int64 rule_id, int64 project_id) throws Error {
            var rule = yield get_rule(rule_id);
            if (rule == null) {
                throw new Error(Quark.from_string("clanker-saddle"), 33,
                    @"No rule exists with id $(rule_id)");
            }
            var existing = yield db.query<RuleProject>()
                .where(expr("rule_id == $0 && project_id == $1",
                    elem<int64?>(rule_id), elem<int64?>(project_id)))
                .materialise_async();
            if (existing.length > 0) {
                return;
            }
            yield db.insert_async<RuleProject>(new RuleProject() {
                rule_id = rule_id,
                project_id = project_id,
                created_at = new DateTime.now_local()
            });
        }

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

        /** The `rule_projects` attachments of `project_id`, oldest first. */
        public async ImmutableLot<RuleProject> list_project_attachments(int64 project_id) throws Error {
            return yield db.query<RuleProject>()
                .where(expr("project_id == $0", elem<int64?>(project_id)))
                .order_by(expr("id"))
                .materialise_async();
        }

        /** The rules attached to `project_id`, attachment order. */
        public async ImmutableLot<Rule> list_rules_for_project(int64 project_id) throws Error {
            var rows = new Vector<Rule>();
            foreach (var link in yield list_project_attachments(project_id)) {
                var rule = yield get_rule(link.rule_id);
                if (rule != null) {
                    rows.add((!)rule);
                }
            }
            return rows.to_immutable_buffer();
        }

        /**
         * Attaches `rule_id` to `task_id`; duplicates are rejected (the
         * pair is unique).
         */
        public async void attach_rule_to_task(int64 rule_id, int64 task_id) throws Error {
            var rule = yield get_rule(rule_id);
            if (rule == null) {
                throw new Error(Quark.from_string("clanker-saddle"), 33,
                    @"No rule exists with id $(rule_id)");
            }
            var existing = yield db.query<TaskRule>()
                .where(expr("rule_id == $0 && task_id == $1",
                    elem<int64?>(rule_id), elem<int64?>(task_id)))
                .materialise_async();
            if (existing.length > 0) {
                return;
            }
            yield db.insert_async<TaskRule>(new TaskRule() {
                rule_id = rule_id,
                task_id = task_id,
                created_at = new DateTime.now_local()
            });
        }

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

        /** The `task_rules` attachments of `task_id`, oldest first. */
        public async ImmutableLot<TaskRule> list_task_attachments(int64 task_id) throws Error {
            return yield db.query<TaskRule>()
                .where(expr("task_id == $0", elem<int64?>(task_id)))
                .order_by(expr("id"))
                .materialise_async();
        }

        /** The rules attached to `task_id`, attachment order. */
        public async ImmutableLot<Rule> list_rules_for_task(int64 task_id) throws Error {
            var rows = new Vector<Rule>();
            foreach (var link in yield list_task_attachments(task_id)) {
                var rule = yield get_rule(link.rule_id);
                if (rule != null) {
                    rows.add((!)rule);
                }
            }
            return rows.to_immutable_buffer();
        }

        /**
         * The effective rule set for a dispatched task, in the wire
         * contract's stable order: the task's own rules, then the primary
         * project's, then the co-developed projects' in link order —
         * deduped by id (reference projects contribute nothing).
         */
        public async ImmutableLot<Rule> effective_rules(TaskEntity task,
                ProjectService projects) throws Error {
            return yield effective_rules_for(task, projects, 0);
        }

        /**
         * The goal-aware variant (plan 12): with `goal_id` > 0 the
         * co-developed expansion walks the GOAL's links instead of the
         * project's — goal work (the agent's run and its worker
         * tasks) scopes its involved repos through the goal.
         */
        public async ImmutableLot<Rule> effective_rules_for(TaskEntity task,
                ProjectService projects, int64 goal_id) throws Error {
            var ordered = new Vector<Rule>();
            // Ids are stringified: the Invercargill collections cannot
            // key (or hash) on value types.
            var seen = new HashSet<string>();

            foreach (var rule in yield list_rules_for_task(task.id)) {
                if (seen.add(rule.id.to_string())) {
                    ordered.add(rule);
                }
            }
            // Goal 8 task 4: standalone tasks (project 0) carry only
            // their own task rules — no project exists to expand.
            if (task.project_id > 0) {
                foreach (var rule in yield list_rules_for_project(task.project_id)) {
                    if (seen.add(rule.id.to_string())) {
                        ordered.add(rule);
                    }
                }
            }
            if (goal_id > 0) {
                foreach (var link in yield db.query<GoalLink>()
                        .where(expr("goal_id == $0", elem<int64?>(goal_id)))
                        .order_by(expr("id"))
                        .materialise_async()) {
                    if (link.relationship != LINK_CO_DEVELOPED) {
                        continue;
                    }
                    foreach (var rule in yield list_rules_for_project(link.project_id)) {
                        if (seen.add(rule.id.to_string())) {
                            ordered.add(rule);
                        }
                    }
                }
            } else if (task.project_id > 0) {
                foreach (var link in yield projects.list_links(task.project_id)) {
                    if (link.relationship != LINK_CO_DEVELOPED) {
                        continue;
                    }
                    foreach (var rule in yield list_rules_for_project(link.linked_project_id)) {
                        if (seen.add(rule.id.to_string())) {
                            ordered.add(rule);
                        }
                    }
                }
            }
            return ordered.to_immutable_buffer();
        }
    }
}