import { randomUUID } from "node:crypto";
import pg from "pg";

import type { ExecutionReport, Milestone, TaskGroup, TaskGroupOverview, TaskItem, TaskStatus, Timeline } from "./contracts.ts";
import type { MdtodoImportPlan } from "./mdtodo-import.ts";

const { Pool } = pg;

const schema = [
  `CREATE TABLE IF NOT EXISTS tasktree_schema_migrations (migration_id TEXT PRIMARY KEY, applied_at TIMESTAMPTZ NOT NULL DEFAULT now())`,
  `CREATE TABLE IF NOT EXISTS tasktree_groups (
    id TEXT PRIMARY KEY, name TEXT NOT NULL, description TEXT NOT NULL DEFAULT '',
    created_at TIMESTAMPTZ NOT NULL DEFAULT now(), updated_at TIMESTAMPTZ NOT NULL DEFAULT now())`,
  `CREATE TABLE IF NOT EXISTS tasktree_tasks (
    id TEXT PRIMARY KEY, group_id TEXT NOT NULL REFERENCES tasktree_groups(id) ON DELETE CASCADE,
    parent_id TEXT REFERENCES tasktree_tasks(id) ON DELETE CASCADE, kind TEXT NOT NULL CHECK (kind IN ('task','subtask','subsubtask')),
    title TEXT NOT NULL, description TEXT NOT NULL DEFAULT '', status TEXT NOT NULL DEFAULT 'pending'
      CHECK (status IN ('pending','in_progress','completed','blocked')),
    start_at TIMESTAMPTZ, due_at TIMESTAMPTZ, sort_order INTEGER NOT NULL DEFAULT 0,
    created_at TIMESTAMPTZ NOT NULL DEFAULT now(), updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    CHECK (due_at IS NULL OR start_at IS NULL OR due_at >= start_at))`,
  `CREATE TABLE IF NOT EXISTS tasktree_milestones (
    id TEXT PRIMARY KEY, group_id TEXT NOT NULL REFERENCES tasktree_groups(id) ON DELETE CASCADE,
    task_id TEXT REFERENCES tasktree_tasks(id) ON DELETE CASCADE, title TEXT NOT NULL,
    occurs_at TIMESTAMPTZ NOT NULL, created_at TIMESTAMPTZ NOT NULL DEFAULT now())`,
  `CREATE TABLE IF NOT EXISTS tasktree_execution_reports (
    id TEXT PRIMARY KEY, task_id TEXT NOT NULL REFERENCES tasktree_tasks(id) ON DELETE CASCADE,
    title TEXT NOT NULL, body TEXT NOT NULL, status TEXT NOT NULL DEFAULT 'succeeded',
    created_at TIMESTAMPTZ NOT NULL DEFAULT now())`,
  `CREATE INDEX IF NOT EXISTS idx_tasktree_tasks_group_order ON tasktree_tasks(group_id, sort_order, created_at)`,
  `CREATE INDEX IF NOT EXISTS idx_tasktree_tasks_parent ON tasktree_tasks(parent_id)`,
  `CREATE INDEX IF NOT EXISTS idx_tasktree_reports_task ON tasktree_execution_reports(task_id, created_at DESC)`
  ,`ALTER TABLE tasktree_tasks DROP CONSTRAINT IF EXISTS tasktree_tasks_kind_check`
  ,`ALTER TABLE tasktree_tasks ADD CONSTRAINT tasktree_tasks_kind_check CHECK (kind IN ('task','subtask','subsubtask'))`
];

export class TaskTreeStore {
  private readonly pool: pg.Pool;
  private ready = false;

  constructor(databaseUrl: string) {
    if (!databaseUrl) throw new Error("TASKTREE_DATABASE_URL or DATABASE_URL is required");
    this.pool = new Pool({ connectionString: databaseUrl, max: 4, connectionTimeoutMillis: 5000, ssl: { rejectUnauthorized: false } });
  }

  async ensureSchema() {
    if (this.ready) return;
    const client = await this.pool.connect();
    try {
      await client.query("BEGIN");
      for (const statement of schema) await client.query(statement);
      await client.query("INSERT INTO tasktree_schema_migrations (migration_id) VALUES ($1),($2) ON CONFLICT DO NOTHING", ["tasktree-20260716-v1", "tasktree-20260717-v2-subsubtask"]);
      await client.query("COMMIT");
      this.ready = true;
    } catch (error) {
      await client.query("ROLLBACK").catch(() => {});
      throw error;
    } finally {
      client.release();
    }
  }

  async health() {
    await this.ensureSchema();
    const result = await this.pool.query("SELECT current_database() AS database, now() AS now");
    return { storage: "native-postgresql", schemaReady: true, database: result.rows[0]?.database, checkedAt: result.rows[0]?.now };
  }

  async listGroups(): Promise<TaskGroup[]> {
    await this.ensureSchema();
    const result = await this.pool.query("SELECT * FROM tasktree_groups ORDER BY updated_at DESC, name");
    return result.rows.map(groupRow);
  }

  async groupOverview(): Promise<TaskGroupOverview[]> {
    await this.ensureSchema();
    const result = await this.pool.query(`
      SELECT g.*,
        COUNT(DISTINCT t.id) FILTER (WHERE t.kind='task')::int AS task_count,
        COUNT(DISTINCT t.id) FILTER (WHERE t.kind='subtask')::int AS subtask_count,
        COUNT(DISTINCT t.id) FILTER (WHERE t.kind='subsubtask')::int AS subsubtask_count,
        COUNT(DISTINCT r.id)::int AS report_count,
        MIN(t.start_at) AS start_at,
        MAX(t.due_at) AS due_at
      FROM tasktree_groups g
      LEFT JOIN tasktree_tasks t ON t.group_id=g.id
      LEFT JOIN tasktree_execution_reports r ON r.task_id=t.id
      GROUP BY g.id
      ORDER BY g.updated_at DESC, g.name
    `);
    return result.rows.map(overviewRow);
  }

  async getGroup(id: string): Promise<TaskGroup | null> {
    await this.ensureSchema();
    const result = await this.pool.query("SELECT * FROM tasktree_groups WHERE id=$1", [id]);
    return result.rows[0] ? groupRow(result.rows[0]) : null;
  }

  async createGroup(name: string, description = ""): Promise<TaskGroup> {
    await this.ensureSchema();
    const result = await this.pool.query("INSERT INTO tasktree_groups (id,name,description) VALUES ($1,$2,$3) RETURNING *", [`tg_${randomUUID()}`, name, description]);
    return groupRow(result.rows[0]);
  }

  async deleteGroup(id: string): Promise<boolean> {
    await this.ensureSchema();
    return (await this.pool.query("DELETE FROM tasktree_groups WHERE id=$1", [id])).rowCount === 1;
  }

  async createTask(input: { groupId: string; title: string; description?: string; startAt?: string; dueAt?: string; parentId?: string }): Promise<TaskItem> {
    await this.ensureSchema();
    let kind = "task";
    if (input.parentId) {
      const parent = await this.pool.query("SELECT group_id,kind FROM tasktree_tasks WHERE id=$1", [input.parentId]);
      if (!parent.rows[0]) throw domainError("parent_not_found", "parent task was not found");
      if (parent.rows[0].group_id !== input.groupId) throw domainError("parent_group_mismatch", "parent task belongs to another taskgroup");
      if (parent.rows[0].kind === "subsubtask") throw domainError("maximum_depth_exceeded", "TaskTree supports task, subtask, and subsubtask only");
      kind = parent.rows[0].kind === "task" ? "subtask" : "subsubtask";
    }
    const result = await this.pool.query(
      `INSERT INTO tasktree_tasks (id,group_id,parent_id,kind,title,description,start_at,due_at,sort_order)
       VALUES ($1,$2,$3,$4,$5,$6,$7,$8,(SELECT COALESCE(MAX(sort_order),-1)+1 FROM tasktree_tasks WHERE group_id=$2)) RETURNING *`,
      [`tt_${randomUUID()}`, input.groupId, input.parentId ?? null, kind, input.title, input.description ?? "", input.startAt ?? null, input.dueAt ?? null]
    );
    return taskRow(result.rows[0]);
  }

  async updateTask(id: string, patch: { title?: string; description?: string; status?: TaskStatus; startAt?: string | null; dueAt?: string | null }): Promise<TaskItem | null> {
    await this.ensureSchema();
    const current = await this.pool.query("SELECT * FROM tasktree_tasks WHERE id=$1", [id]);
    if (!current.rows[0]) return null;
    const row = taskRow(current.rows[0]);
    const result = await this.pool.query(
      `UPDATE tasktree_tasks SET title=$2,description=$3,status=$4,start_at=$5,due_at=$6,updated_at=now() WHERE id=$1 RETURNING *`,
      [id, patch.title ?? row.title, patch.description ?? row.description, patch.status ?? row.status,
        patch.startAt === undefined ? row.startAt : patch.startAt, patch.dueAt === undefined ? row.dueAt : patch.dueAt]
    );
    return taskRow(result.rows[0]);
  }

  async deleteTask(id: string): Promise<boolean> {
    await this.ensureSchema();
    return (await this.pool.query("DELETE FROM tasktree_tasks WHERE id=$1", [id])).rowCount === 1;
  }

  async createMilestone(input: { groupId: string; title: string; occursAt: string; taskId?: string }): Promise<Milestone> {
    await this.ensureSchema();
    const result = await this.pool.query(
      "INSERT INTO tasktree_milestones (id,group_id,task_id,title,occurs_at) VALUES ($1,$2,$3,$4,$5) RETURNING *",
      [`tm_${randomUUID()}`, input.groupId, input.taskId ?? null, input.title, input.occursAt]
    );
    return milestoneRow(result.rows[0]);
  }

  async createReport(input: { taskId: string; title: string; body: string; status?: string }): Promise<ExecutionReport> {
    await this.ensureSchema();
    const result = await this.pool.query(
      "INSERT INTO tasktree_execution_reports (id,task_id,title,body,status) VALUES ($1,$2,$3,$4,$5) RETURNING *",
      [`tr_${randomUUID()}`, input.taskId, input.title, input.body, input.status ?? "succeeded"]
    );
    return reportRow(result.rows[0]);
  }

  async importMdtodo(plan: MdtodoImportPlan) {
    await this.ensureSchema();
    const client = await this.pool.connect();
    const groupId = `tg_${randomUUID()}`;
    const taskIds = new Map<string, string>();
    try {
      await client.query("BEGIN");
      const groupResult = await client.query(
        "INSERT INTO tasktree_groups (id,name,description) VALUES ($1,$2,$3) RETURNING *",
        [groupId, plan.groupName, plan.groupDescription]
      );
      for (let index = 0; index < plan.tasks.length; index += 1) {
        const task = plan.tasks[index];
        const taskId = `tt_${randomUUID()}`;
        taskIds.set(task.sourceId, taskId);
        const parentId = task.parentSourceId ? taskIds.get(task.parentSourceId) ?? null : null;
        const parentTask = parentId ? plan.tasks.find((candidate) => candidate.sourceId === task.parentSourceId) : null;
        const kind = !parentId ? "task" : parentTask?.parentSourceId ? "subsubtask" : "subtask";
        await client.query(
          `INSERT INTO tasktree_tasks (id,group_id,parent_id,kind,title,description,status,start_at,due_at,sort_order)
           VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10)`,
          [taskId, groupId, parentId, kind, task.title, task.description, task.status, task.startAt, task.dueAt, index]
        );
        for (const report of task.reports) {
          await client.query(
            "INSERT INTO tasktree_execution_reports (id,task_id,title,body,status,created_at) VALUES ($1,$2,$3,$4,$5,$6)",
            [`tr_${randomUUID()}`, taskId, report.title, report.body, report.status, report.createdAt]
          );
        }
      }
      await client.query("COMMIT");
      return { dryRun: false, sourcePath: plan.sourcePath, group: groupRow(groupResult.rows[0]), parserMode: plan.parserMode, summary: plan.summary, warnings: plan.warnings };
    } catch (error) {
      await client.query("ROLLBACK").catch(() => {});
      throw error;
    } finally {
      client.release();
    }
  }

  async timeline(groupId: string): Promise<Timeline | null> {
    await this.ensureSchema();
    const group = await this.getGroup(groupId);
    if (!group) return null;
    const [tasks, milestones, reports] = await Promise.all([
      this.pool.query("SELECT * FROM tasktree_tasks WHERE group_id=$1 ORDER BY sort_order,created_at", [groupId]),
      this.pool.query("SELECT * FROM tasktree_milestones WHERE group_id=$1 ORDER BY occurs_at", [groupId]),
      this.pool.query("SELECT r.* FROM tasktree_execution_reports r JOIN tasktree_tasks t ON t.id=r.task_id WHERE t.group_id=$1 ORDER BY r.created_at DESC", [groupId])
    ]);
    return { group, tasks: tasks.rows.map(taskRow), milestones: milestones.rows.map(milestoneRow), reports: reports.rows.map(reportRow) };
  }

  async close() { await this.pool.end(); }
}

function groupRow(row: any): TaskGroup { return { id: row.id, name: row.name, description: row.description, createdAt: iso(row.created_at), updatedAt: iso(row.updated_at) }; }
function overviewRow(row: any): TaskGroupOverview { return { group: groupRow(row), taskCount: Number(row.task_count), subtaskCount: Number(row.subtask_count), subsubtaskCount: Number(row.subsubtask_count), reportCount: Number(row.report_count), startAt: nullableIso(row.start_at), dueAt: nullableIso(row.due_at) }; }
function taskRow(row: any): TaskItem { return { id: row.id, groupId: row.group_id, parentId: row.parent_id, kind: row.kind, title: row.title, description: row.description, status: row.status, startAt: nullableIso(row.start_at), dueAt: nullableIso(row.due_at), sortOrder: row.sort_order, createdAt: iso(row.created_at), updatedAt: iso(row.updated_at) }; }
function milestoneRow(row: any): Milestone { return { id: row.id, groupId: row.group_id, taskId: row.task_id, title: row.title, occursAt: iso(row.occurs_at), createdAt: iso(row.created_at) }; }
function reportRow(row: any): ExecutionReport { return { id: row.id, taskId: row.task_id, title: row.title, body: row.body, status: row.status, createdAt: iso(row.created_at) }; }
function iso(value: unknown): string { return new Date(value as any).toISOString(); }
function nullableIso(value: unknown): string | null { return value == null ? null : iso(value); }
function domainError(code: string, message: string) { return Object.assign(new Error(message), { code }); }