import { Injectable, NotFoundException } from '@nestjs/common';
import type {
  AutomationTriggerType,
  SuggestionIntent,
  TaskPriority,
} from '../../generated/prisma';
import { PermissionResolverService } from '../auth/permissions/permission-resolver.service';
import { readRule } from '../automation/rule-config';
import { LIVING_COLONY_WHERE } from '../colonies/colony-status';
import {
  addDays,
  berlinDayOf,
  berlinToday,
  daysBetween,
  dayToDate,
} from '../common/dates';
import { PrismaService } from '../prisma/prisma.service';
import { SeasonService } from '../season/season.service';
import {
  inspectionDueOn,
  inspectionIntervalOf,
} from '../season/inspection-due';
import type { SeasonSegmentKey, SeasonState } from '../season/season-types';
import { buildEvidenceLookup } from '../suggestions/evidence-lookup';
import { renderSuggestion } from '../suggestions/suggestion-texts';
import { SuggestionViewsService } from '../suggestions/suggestion-views.service';
import {
  INTENT_OF_LEGACY_TRIGGER,
  type SuggestionEvidence,
} from '../suggestions/suggestion.types';
import {
  isInWindow,
  withdrawalWindowOf,
} from '../treatments/withdrawal-window';
import {
  compareSources,
  topSteps,
  type ColonyNextSteps,
  type NextStep,
  type StepSource,
} from './next-step-ranking';

export interface AutopilotToday {
  nextStep: (NextStep & { colonyId: string; colonyCode: string }) | null;
  /** Colonies whose inspection is due today or overdue (`dueOn <= today`), not those coming up. */
  inspectionDue: {
    apiaryId: string;
    apiaryName: string;
    segment: SeasonSegmentKey;
    intervalDays: number | null;
    colonies: {
      id: string;
      code: string;
      dueOn: string;
      overdueDays: number;
    }[];
  }[];
  suggestionsOpen: number;
  seasons: {
    apiaryId: string;
    apiaryName: string;
    segment: SeasonSegmentKey;
    phase: ColonyNextSteps['phase'];
    phaseSource: ColonyNextSteps['phaseSource'];
  }[];
  tasksVisible: boolean;
}

/** Open suggestions of HIGH / URGENT priority that the caller may see. */
export interface WarningCount {
  warnings: number;
  critical: number;
}

interface ColonyComputation {
  code: string;
  apiaryId: string;
  /** Leading source of the first step, for the comparison across colonies. */
  head: StepSource | null;
  view: ColonyNextSteps;
}

interface Computation {
  colonies: Map<string, ColonyComputation>;
  seasons: Map<string, SeasonState>;
  intervalDays: Readonly<
    Record<Exclude<SeasonSegmentKey, 'WINTERRUHE'>, number>
  >;
}

/** A withdrawal period longer than this is not looked for. */
const WITHDRAWAL_LOOKBACK_DAYS = 400;
const OPEN_TASK_STATUSES = ['OPEN', 'IN_PROGRESS'] as const;
const WARNING_PRIORITIES: readonly TaskPriority[] = ['HIGH', 'URGENT'];

/** The intent an open task stands for; null for a plain task. */
function taskIntentOf(task: {
  sourceSuggestion: { intent: SuggestionIntent } | null;
  sourceAutomationTrigger: AutomationTriggerType | null;
}): SuggestionIntent | null {
  return (
    task.sourceSuggestion?.intent ??
    (task.sourceAutomationTrigger === null
      ? null
      : (INTENT_OF_LEGACY_TRIGGER[task.sourceAutomationTrigger] ?? null))
  );
}

function byCode(a: { code: string }, b: { code: string }): number {
  return a.code.localeCompare(b.code, 'de', { numeric: true });
}

/**
 * "The next 3 steps" of a colony (Spec 8.4, 8.5) and the day overview: what
 * the user may see of the open tasks and suggestions, ranked, merged by form
 * and cut to `maxStepsPerColony`. Reads only; a fixed number of queries for
 * any number of colonies.
 */
@Injectable()
export class NextStepsService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly permissionResolver: PermissionResolverService,
    private readonly seasons: SeasonService,
    private readonly suggestionViews: SuggestionViewsService,
  ) {}

  async forColony(
    colonyId: string,
    userId: string,
    today: string = berlinToday(),
  ): Promise<ColonyNextSteps> {
    const view = (await this.forColonies([colonyId], userId, today)).get(
      colonyId,
    );
    if (view === undefined) {
      throw new NotFoundException('Colony not found');
    }
    return view;
  }

  /** Unknown colonies are left out of the map. */
  async forColonies(
    colonyIds: readonly string[],
    userId: string,
    today: string = berlinToday(),
    permissions?: ReadonlySet<string>,
  ): Promise<Map<string, ColonyNextSteps>> {
    const held =
      permissions ?? (await this.permissionResolver.getPermissions(userId));
    const { colonies } = await this.compute(colonyIds, held, today);
    return new Map(
      [...colonies].map(([id, colony]) => [id, colony.view] as const),
    );
  }

  /**
   * Open HIGH / URGENT suggestions per colony: the "warnings" and
   * "critical" of the colony traffic light. Only what the user may see
   * (`tasks:read` and the permission of each suggestion).
   */
  async warningCounts(
    colonyIds: readonly string[],
    userId: string,
    permissions?: ReadonlySet<string>,
  ): Promise<Map<string, WarningCount>> {
    const held =
      permissions ?? (await this.permissionResolver.getPermissions(userId));
    const counts = new Map<string, WarningCount>();
    if (!held.has('tasks:read') || colonyIds.length === 0) {
      return counts;
    }
    const groups = await this.prisma.suggestion.groupBy({
      by: ['colonyId', 'priority'],
      where: {
        AND: [
          this.suggestionViews.visibleWhere(held),
          {
            status: 'OPEN',
            colonyId: { in: [...colonyIds] },
            priority: { in: [...WARNING_PRIORITIES] },
          },
        ],
      },
      _count: { _all: true },
    });
    for (const group of groups) {
      if (group.colonyId === null) {
        continue;
      }
      const current = counts.get(group.colonyId) ?? {
        warnings: 0,
        critical: 0,
      };
      counts.set(
        group.colonyId,
        group.priority === 'URGENT'
          ? { ...current, critical: group._count._all }
          : { ...current, warnings: group._count._all },
      );
    }
    return counts;
  }

  async today(
    userId: string,
    today: string = berlinToday(),
  ): Promise<AutopilotToday> {
    const held = await this.permissionResolver.getPermissions(userId);
    const living = await this.prisma.colony.findMany({
      where: LIVING_COLONY_WHERE,
      select: { id: true },
    });
    const { colonies, seasons, intervalDays } = await this.compute(
      living.map((colony) => colony.id),
      held,
      today,
    );
    const apiaries = await this.prisma.apiary.findMany({
      where: { id: { in: [...seasons.keys()] } },
      select: { id: true, name: true },
    });
    const apiaryName = new Map(apiaries.map((a) => [a.id, a.name] as const));
    const nameOf = (apiaryId: string): string => apiaryName.get(apiaryId) ?? '';
    const suggestionsOpen = held.has('tasks:read')
      ? await this.prisma.suggestion.count({
          where: {
            AND: [this.suggestionViews.visibleWhere(held), { status: 'OPEN' }],
          },
        })
      : 0;
    const sortedApiaries = [...seasons.values()].sort((a, b) =>
      nameOf(a.apiaryId).localeCompare(nameOf(b.apiaryId), 'de', {
        numeric: true,
      }),
    );
    return {
      nextStep: this.mostUrgent(colonies, today),
      inspectionDue: this.dueInspections(
        colonies,
        sortedApiaries,
        intervalDays,
        nameOf,
        today,
      ),
      suggestionsOpen,
      seasons: sortedApiaries.map((season) => ({
        apiaryId: season.apiaryId,
        apiaryName: nameOf(season.apiaryId),
        segment: season.segment,
        phase: season.phase,
        phaseSource: season.phaseSource,
      })),
      tasksVisible: held.has('tasks:read'),
    };
  }

  /**
   * Only the due inspections of all living colonies, whatever the reader
   * may see (the caller filters by right): the digest's input.
   */
  async inspectionDueAll(
    today: string = berlinToday(),
  ): Promise<AutopilotToday['inspectionDue']> {
    const living = await this.prisma.colony.findMany({
      where: LIVING_COLONY_WHERE,
      select: { id: true },
    });
    const { colonies, seasons, intervalDays } = await this.compute(
      living.map((colony) => colony.id),
      new Set(['inspections:read']),
      today,
    );
    const apiaries = await this.prisma.apiary.findMany({
      where: { id: { in: [...seasons.keys()] } },
      select: { id: true, name: true },
    });
    const names = new Map(apiaries.map((a) => [a.id, a.name] as const));
    const nameOf = (apiaryId: string): string => names.get(apiaryId) ?? '';
    const sorted = [...seasons.values()].sort((a, b) =>
      nameOf(a.apiaryId).localeCompare(nameOf(b.apiaryId), 'de', {
        numeric: true,
      }),
    );
    return this.dueInspections(colonies, sorted, intervalDays, nameOf, today);
  }

  private dueInspections(
    colonies: ReadonlyMap<string, ColonyComputation>,
    sortedSeasons: readonly SeasonState[],
    intervalDays: Computation['intervalDays'],
    nameOf: (apiaryId: string) => string,
    today: string,
  ): AutopilotToday['inspectionDue'] {
    return sortedSeasons.flatMap((season) => {
      const due = [...colonies]
        .filter(
          ([, c]) =>
            c.apiaryId === season.apiaryId &&
            c.view.inspectionDueOn !== null &&
            c.view.inspectionDueOn <= today,
        )
        .map(([id, c]) => ({
          id,
          code: c.code,
          dueOn: c.view.inspectionDueOn ?? today,
          overdueDays: daysBetween(c.view.inspectionDueOn ?? today, today),
        }))
        .sort((a, b) => a.dueOn.localeCompare(b.dueOn) || byCode(a, b));
      return due.length === 0
        ? []
        : [
            {
              apiaryId: season.apiaryId,
              apiaryName: nameOf(season.apiaryId),
              segment: season.segment,
              intervalDays: inspectionIntervalOf(season.segment, intervalDays),
              colonies: due,
            },
          ];
    });
  }

  private mostUrgent(
    colonies: ReadonlyMap<string, ColonyComputation>,
    today: string,
  ): AutopilotToday['nextStep'] {
    const candidates = [...colonies].flatMap(([colonyId, colony]) =>
      colony.head === null || colony.view.steps.length === 0
        ? []
        : [{ colonyId, colony, head: colony.head }],
    );
    candidates.sort((a, b) => compareSources(a.head, b.head, today));
    const best = candidates.at(0);
    return best === undefined
      ? null
      : {
          ...best.colony.view.steps[0],
          colonyId: best.colonyId,
          colonyCode: best.colony.code,
        };
  }

  private async compute(
    colonyIds: readonly string[],
    held: ReadonlySet<string>,
    today: string,
  ): Promise<Computation> {
    const ids = [...new Set(colonyIds)];
    const rows =
      ids.length === 0
        ? []
        : await this.prisma.colony.findMany({
            where: { id: { in: ids } },
            select: { id: true, code: true, apiaryId: true, createdAt: true },
          });
    const [states, interval, autopilot] = await Promise.all([
      this.seasons.statesFor(
        this.prisma,
        rows.map((row) => row.apiaryId),
        today,
      ),
      readRule(this.prisma, 'INSPECTION_INTERVAL'),
      readRule(this.prisma, 'SEASON_AUTOPILOT'),
    ]);
    const foundIds = rows.map((row) => row.id);
    const [lastInspections, sources, withdrawals] = await Promise.all([
      this.lastInspectionDays(foundIds, held),
      this.stepSources(foundIds, held, today),
      this.withdrawalUntil(foundIds, held, today),
    ]);
    const colonies = new Map<string, ColonyComputation>();
    for (const row of rows) {
      const season = states.get(row.apiaryId);
      if (season === undefined) {
        continue;
      }
      const due = interval.active
        ? inspectionDueOn(
            {
              createdOn: berlinDayOf(row.createdAt),
              lastInspectedOn: lastInspections.get(row.id) ?? null,
            },
            season,
            interval.config,
          )
        : null;
      const own = sources.get(row.id) ?? [];
      const steps = topSteps(own, today, {
        limit: autopilot.config.maxStepsPerColony,
        canAccept: held.has('tasks:create'),
      });
      colonies.set(row.id, {
        code: row.code,
        apiaryId: row.apiaryId,
        head: this.headOf(own, steps),
        view: {
          colonyId: row.id,
          segment: season.segment,
          phase: season.phase,
          phaseSource: season.phaseSource,
          inspectionDueOn:
            due !== null && held.has('inspections:read') ? due.dueOn : null,
          withdrawalUntil: withdrawals.get(row.id) ?? null,
          steps,
        },
      });
    }
    return {
      colonies,
      seasons: states,
      intervalDays: interval.config.intervalDays,
    };
  }

  /** The source that stands for the first step (for the cross-colony order). */
  private headOf(
    own: readonly StepSource[],
    steps: readonly NextStep[],
  ): StepSource | null {
    const first = steps.at(0);
    if (first === undefined) {
      return null;
    }
    const byId = new Map(own.map((source) => [source.id, source] as const));
    const id =
      first.suggestionIds.at(0) ??
      (first.action.type === 'OPEN_TASK' ? first.action.taskId : null);
    return id === null ? null : (byId.get(id) ?? null);
  }

  /** Last inspection day per colony; nothing without `inspections:read`. */
  private async lastInspectionDays(
    colonyIds: readonly string[],
    held: ReadonlySet<string>,
  ): Promise<Map<string, string>> {
    const days = new Map<string, string>();
    if (!held.has('inspections:read') || colonyIds.length === 0) {
      return days;
    }
    const groups = await this.prisma.inspection.groupBy({
      by: ['colonyId'],
      where: { colonyId: { in: [...colonyIds] } },
      _max: { date: true },
    });
    for (const group of groups) {
      if (group._max.date) {
        days.set(group.colonyId, berlinDayOf(group._max.date));
      }
    }
    return days;
  }

  /** The youngest running withdrawal period per colony (treatments:read). */
  private async withdrawalUntil(
    colonyIds: readonly string[],
    held: ReadonlySet<string>,
    today: string,
  ): Promise<Map<string, string>> {
    const until = new Map<string, string>();
    if (!held.has('treatments:read') || colonyIds.length === 0) {
      return until;
    }
    const cutoff = dayToDate(addDays(today, -WITHDRAWAL_LOOKBACK_DAYS));
    const treatments = await this.prisma.treatment.findMany({
      where: {
        colonyId: { in: [...colonyIds] },
        withdrawalPeriodDays: { not: null },
        OR: [{ endDate: { gte: cutoff } }, { date: { gte: cutoff } }],
      },
      select: {
        id: true,
        colonyId: true,
        product: true,
        date: true,
        startDate: true,
        endDate: true,
        withdrawalPeriodDays: true,
      },
    });
    for (const treatment of treatments) {
      const window = withdrawalWindowOf(treatment);
      if (window === null || !isInWindow(window, today)) {
        continue;
      }
      const current = until.get(treatment.colonyId);
      if (current === undefined || window.untilDay > current) {
        until.set(treatment.colonyId, window.untilDay);
      }
    }
    return until;
  }

  /**
   * Open suggestions (visible ones, and only with `tasks:read`) and open
   * tasks (`tasks:read`) of the colonies, as rankable sources.
   */
  private async stepSources(
    colonyIds: readonly string[],
    held: ReadonlySet<string>,
    today: string,
  ): Promise<Map<string, StepSource[]>> {
    const sources = new Map<string, StepSource[]>();
    if (!held.has('tasks:read') || colonyIds.length === 0) {
      return sources;
    }
    const [suggestions, tasks] = await Promise.all([
      this.prisma.suggestion.findMany({
        where: {
          AND: [
            this.suggestionViews.visibleWhere(held),
            { status: 'OPEN', colonyId: { in: [...colonyIds] } },
          ],
        },
        select: {
          id: true,
          ruleKey: true,
          reasonCode: true,
          evidence: true,
          intent: true,
          mode: true,
          status: true,
          priority: true,
          dueDate: true,
          createdAt: true,
          colonyId: true,
        },
      }),
      this.prisma.task.findMany({
        where: {
          status: { in: [...OPEN_TASK_STATUSES] },
          relatedType: 'COLONY',
          relatedId: { in: [...colonyIds] },
        },
        select: {
          id: true,
          title: true,
          status: true,
          priority: true,
          dueDate: true,
          createdAt: true,
          relatedId: true,
          sourceAutomationTrigger: true,
          sourceSuggestion: { select: { intent: true } },
        },
      }),
    ]);
    const [lookup, templates] = await Promise.all([
      buildEvidenceLookup(
        this.prisma,
        suggestions.map((row) => row.evidence as SuggestionEvidence),
      ),
      this.titleTemplates(suggestions.map((row) => row.ruleKey)),
    ]);
    const add = (colonyId: string, source: StepSource): void => {
      sources.set(colonyId, [...(sources.get(colonyId) ?? []), source]);
    };
    // One open thing per intent and colony: an open task of the same intent
    // (accepted suggestion or legacy rule task) hides an open suggestion.
    const openTaskIntents = new Set(
      tasks.flatMap((row) => {
        const intent = taskIntentOf(row);
        return row.relatedId === null || intent === null
          ? []
          : [`${row.relatedId}|${intent}`];
      }),
    );
    for (const row of suggestions) {
      if (
        row.colonyId === null ||
        openTaskIntents.has(`${row.colonyId}|${row.intent}`)
      ) {
        continue;
      }
      const text = renderSuggestion(
        row,
        lookup,
        today,
        templates.get(row.ruleKey),
      );
      add(row.colonyId, {
        kind: 'SUGGESTION',
        id: row.id,
        intent: row.intent,
        mode: row.mode,
        status: row.status,
        priority: row.priority,
        dueOn: row.dueDate === null ? null : berlinDayOf(row.dueDate),
        createdAt: row.createdAt,
        title: text.title,
        reasons: text.reasons,
        colonyId: row.colonyId,
      });
    }
    for (const row of tasks) {
      if (row.relatedId === null) {
        continue;
      }
      add(row.relatedId, {
        kind: 'TASK',
        id: row.id,
        intent: taskIntentOf(row),
        mode: null,
        status: row.status,
        priority: row.priority,
        dueOn: row.dueDate === null ? null : berlinDayOf(row.dueDate),
        createdAt: row.createdAt,
        title: row.title,
        reasons: [],
        colonyId: row.relatedId,
      });
    }
    return sources;
  }

  /** The `actionTemplate` of each rule replaces the title of its suggestions. */
  private async titleTemplates(
    ruleKeys: readonly AutomationTriggerType[],
  ): Promise<Map<AutomationTriggerType, string | null>> {
    if (ruleKeys.length === 0) {
      return new Map();
    }
    const rules = await this.prisma.automationRule.findMany({
      where: { triggerType: { in: [...new Set(ruleKeys)] } },
      select: { triggerType: true, actionTemplate: true },
    });
    return new Map(
      rules.map((rule) => [rule.triggerType, rule.actionTemplate] as const),
    );
  }
}