import {
  ActivityReadModel,
  AgendaItemReadModel,
  HomeProjectReadModel,
  HomeReadModel,
  HomeSprintReadModel,
  IssueReadModel,
  IssueTimelineEntry,
  OnlineReadModel,
  ProjectReadModel,
  ProjectRole,
  ReleaseReadModel,
  ReleaseStatus,
  SprintReadModel,
  SprintStatus,
  StatusCategory,
  SuggestionReadModel,
} from '@task-stream/api/tracker/domain';
import { PROPOSAL_LABEL } from '../proposals';
import { guestOnly } from '../queries/read-access';
import { stepsByIssue } from './analytics';
import { sprintPulse } from './insights';

/*
 * The home page beyond «my work»: what comes this week, what moves in my
 * projects, how the week goes, and what to do when nothing is mine. Pure,
 * like the statistics.
 */

const DAY = 86_400_000;
const CLOSED = [StatusCategory.DONE, StatusCategory.CANCELLED];
const OPEN = [
  StatusCategory.TODO,
  StatusCategory.IN_PROGRESS,
  StatusCategory.QA,
];

export interface HomeProjectInput {
  project: ProjectReadModel;
  issues: IssueReadModel[];
  timeline: IssueTimelineEntry[];
  sprints: SprintReadModel[];
  releases: ReleaseReadModel[];
  /** Activity per day of the last 14 days, oldest first. */
  activity: number[];
}

export interface HomeInput {
  viewerId: string;
  projects: HomeProjectInput[];
  /** Latest activity of the projects I see whole, newest first. */
  activity: ActivityReadModel[];
  hasCalendar: boolean;
  online: OnlineReadModel[];
  now: Date;
}

const utcDay = (time: number) =>
  Date.UTC(
    new Date(time).getUTCFullYear(),
    new Date(time).getUTCMonth(),
    new Date(time).getUTCDate(),
  );
const dayString = (time: number) => new Date(time).toISOString().slice(0, 10);

export function computeHome(input: HomeInput): HomeReadModel {
  const now = input.now.getTime();
  const today = utcDay(now);
  const todayStr = dayString(today);
  const weekEnd = dayString(today + 6 * DAY);
  const me = input.viewerId;
  const whole = input.projects.filter((p) => !guestOnly(p.project, me));

  // --- Agenda: the next 7 days ---
  const agenda: AgendaItemReadModel[] = [];
  for (const { project, issues, sprints, releases } of input.projects) {
    for (const issue of issues) {
      if (issue.trashedAt || CLOSED.includes(issue.statusCategory)) continue;
      const due = issue.dueDate?.slice(0, 10);
      if (!due || due < todayStr || due > weekEnd) continue;
      if (
        issue.assignee?.id !== me &&
        !(issue.watchers ?? []).some((w) => w.id === me)
      )
        continue;
      agenda.push({
        day: due,
        kind: 'ISSUE',
        projectKey: project.key,
        title: issue.title,
        issueKey: issue.key,
      });
    }
    if (guestOnly(project, me)) continue;
    for (const sprint of sprints)
      if (
        sprint.status === SprintStatus.ACTIVE &&
        sprint.endDate >= todayStr &&
        sprint.endDate <= weekEnd
      )
        agenda.push({
          day: sprint.endDate,
          kind: 'SPRINT_END',
          projectKey: project.key,
          title: sprint.name,
          issueKey: null,
        });
    for (const release of releases) {
      const target = release.targetDate?.slice(0, 10);
      if (
        release.status === ReleaseStatus.PLANNED &&
        target &&
        target >= todayStr &&
        target <= weekEnd
      )
        agenda.push({
          day: target,
          kind: 'RELEASE',
          projectKey: project.key,
          title: release.name,
          issueKey: null,
        });
    }
  }
  agenda.sort(
    (a, b) => a.day.localeCompare(b.day) || a.kind.localeCompare(b.kind),
  );

  // --- Finished per day: the team's and mine ---
  const teamPerDay = new Array<number>(14).fill(0);
  const minePerDay = new Map<number, number>();
  for (const { issues, timeline } of whole) {
    const steps = stepsByIssue(issues, timeline);
    for (const list of steps.values())
      list.forEach((step, i) => {
        if (step.category !== StatusCategory.DONE) return;
        if (i > 0 && list[i - 1].category === StatusCategory.DONE) return;
        if (i === 0) return; // created already done: nobody finished it
        const day = utcDay(step.at);
        const ago = Math.round((today - day) / DAY);
        if (ago >= 0 && ago < 14) teamPerDay[13 - ago]++;
        if (step.assigneeId === me)
          minePerDay.set(day, (minePerDay.get(day) ?? 0) + 1);
      });
  }
  const sum = (from: number, to: number) =>
    teamPerDay.slice(from, to).reduce((a, b) => a + b, 0);
  const mine = (daysAgoFrom: number, daysAgoTo: number) => {
    let total = 0;
    for (let ago = daysAgoFrom; ago < daysAgoTo; ago++)
      total += minePerDay.get(today - ago * DAY) ?? 0;
    return total;
  };
  // A streak counts up to today, or up to yesterday if today is still empty.
  let streak = 0;
  for (
    let ago = minePerDay.get(today) ? 0 : 1;
    minePerDay.get(today - ago * DAY);
    ago++
  )
    streak++;

  // --- Sprints and project cards ---
  const sprints: HomeSprintReadModel[] = [];
  const projects: HomeProjectReadModel[] = [];
  for (const { project, issues, sprints: all, activity } of whole) {
    const live = issues.filter((i) => !i.trashedAt);
    const active = all.find((s) => s.status === SprintStatus.ACTIVE);
    const pulse = active ? sprintPulse(active, live, now) : null;
    if (pulse)
      sprints.push({
        projectKey: project.key,
        projectName: project.name,
        sprint: pulse,
      });
    projects.push({
      projectId: project.id,
      open: live.filter((i) => !CLOSED.includes(i.statusCategory)).length,
      overdue: live.filter(
        (i) =>
          !CLOSED.includes(i.statusCategory) &&
          !!i.dueDate &&
          i.dueDate.slice(0, 10) < todayStr,
      ).length,
      activity,
      sprint: pulse
        ? {
            name: pulse.name,
            percent: pulse.points
              ? Math.round((pulse.donePoints / pulse.points) * 100)
              : pulse.tickets
                ? Math.round((pulse.doneTickets / pulse.tickets) * 100)
                : 0,
            behind: pulse.behind,
          }
        : null,
    });
  }

  // --- Suggestions, for when nothing is mine ---
  const suggestions: SuggestionReadModel[] = [];
  for (const { project, issues } of whole) {
    const role = project.members.find((m) => m.user.id === me)?.role;
    if (!role || role === ProjectRole.VIEWER) continue;
    const open = issues.filter(
      (i) => !i.trashedAt && OPEN.includes(i.statusCategory),
    );
    const unassigned = open.filter((i) => !i.assignee).length;
    if (unassigned)
      suggestions.push({
        kind: 'UNASSIGNED',
        projectKey: project.key,
        count: unassigned,
      });
    const qa = open.filter(
      (i) => i.statusCategory === StatusCategory.QA,
    ).length;
    if (qa)
      suggestions.push({
        kind: 'QA_WAITING',
        projectKey: project.key,
        count: qa,
      });
    if (role === ProjectRole.OWNER || role === ProjectRole.ADMIN) {
      const proposals = open.filter(
        (i) =>
          i.statusCategory === StatusCategory.TODO &&
          i.labels.includes(PROPOSAL_LABEL),
      ).length;
      if (proposals)
        suggestions.push({
          kind: 'PROPOSALS',
          projectKey: project.key,
          count: proposals,
        });
    }
  }
  suggestions.sort((a, b) => b.count - a.count);

  return {
    agenda,
    activity: input.activity,
    team: { perDay: teamPerDay, thisWeek: sum(7, 14), lastWeek: sum(0, 7) },
    me: { thisWeek: mine(0, 7), lastWeek: mine(7, 14), streak },
    sprints,
    projects,
    suggestions: suggestions.slice(0, 5),
    firstSteps: {
      project: input.projects.length > 0,
      invited: input.projects.some(
        (p) =>
          p.project.members.length > 1 &&
          p.project.members.some(
            (m) =>
              m.user.id === me &&
              (m.role === ProjectRole.OWNER || m.role === ProjectRole.ADMIN),
          ),
      ),
      ticket: input.projects.some((p) =>
        p.issues.some((i) => i.reporter?.id === me),
      ),
      calendar: input.hasCalendar,
    },
    online: input.online,
  };
}

/** The last 14 UTC days (oldest first), as `YYYY-MM-DD`. */
export function lastDays(now: Date, count = 14): string[] {
  const today = utcDay(now.getTime());
  return Array.from({ length: count }, (_, n) =>
    dayString(today - (count - 1 - n) * DAY),
  );
}