import { createAiClient, isAiConfigured, loggedAiCall, parseAiError } from "../ai-client.js";
import { controllerProcedure, createTRPCRouter } from "../trpc.js";
import { TRPCError } from "@trpc/server";
import { z } from "zod";
import { buildInsightSnapshot, type InsightsDbAccess } from "./insights-anomalies.js";

/**
 * Count business days between two dates (Mon–Fri).
 */
function countBusinessDays(start: Date, end: Date): number {
  let count = 0;
  const d = new Date(start);
  while (d <= end) {
    const dow = d.getDay();
    if (dow !== 0 && dow !== 6) count++;
    d.setDate(d.getDate() + 1);
  }
  return count;
}

// ─── Router ──────────────────────────────────────────────────────────────────

export const insightsRouter = createTRPCRouter({
  getAnomalyDetail: controllerProcedure.query(async ({ ctx }) => {
    const snapshot = await buildInsightSnapshot(ctx.db as unknown as InsightsDbAccess);
    return {
      anomalies: snapshot.anomalies,
      count: snapshot.anomalies.length,
    };
  }),

  /**
   * Generate an AI-powered executive narrative for a project.
   * Caches the result in the project's dynamicFields.aiNarrative to avoid
   * calling the AI on every click.
   */
  generateProjectNarrative: controllerProcedure
    .input(z.object({ projectId: z.string() }))
    .mutation(async ({ ctx, input }) => {
      const [project, settings] = await Promise.all([
        ctx.db.project.findUnique({
          where: { id: input.projectId },
          include: {
            demandRequirements: {
              select: {
                id: true,
                role: true,
                headcount: true,
                hoursPerDay: true,
                startDate: true,
                endDate: true,
                status: true,
                _count: { select: { assignments: true } },
              },
            },
            assignments: {
              select: {
                id: true,
                role: true,
                hoursPerDay: true,
                startDate: true,
                endDate: true,
                status: true,
                dailyCostCents: true,
                resource: { select: { displayName: true } },
              },
            },
          },
        }),
        ctx.db.systemSettings.findUnique({ where: { id: "singleton" } }),
      ]);

      if (!project) {
        throw new TRPCError({ code: "NOT_FOUND", message: "Project not found" });
      }

      if (!isAiConfigured(settings)) {
        throw new TRPCError({
          code: "PRECONDITION_FAILED",
          message: "AI is not configured. Please set credentials in Admin \u2192 Settings.",
        });
      }

      // Build context data for the prompt
      const now = new Date();
      const totalDays = countBusinessDays(project.startDate, project.endDate);
      const elapsedDays = countBusinessDays(project.startDate, now < project.endDate ? now : project.endDate);
      const progressPercent = totalDays > 0 ? Math.round((elapsedDays / totalDays) * 100) : 0;

      const totalDemandHeadcount = project.demandRequirements.reduce((s, d) => s + d.headcount, 0);
      const filledDemandHeadcount = project.demandRequirements.reduce(
        (s, d) => s + Math.min(d._count.assignments, d.headcount),
        0,
      );
      const staffingPercent = totalDemandHeadcount > 0
        ? Math.round((filledDemandHeadcount / totalDemandHeadcount) * 100)
        : 100;

      // Estimated cost from assignments
      const totalCostCents = project.assignments.reduce((s, a) => {
        const days = countBusinessDays(a.startDate, a.endDate);
        return s + a.dailyCostCents * days;
      }, 0);

      const budgetCents = project.budgetCents;
      const budgetUsedPercent = budgetCents > 0 ? Math.round((totalCostCents / budgetCents) * 100) : 0;

      const overrunAssignments = project.assignments.filter(
        (a) => a.endDate > project.endDate,
      );

      const dataContext = [
        `Project: ${project.name} (${project.shortCode})`,
        `Status: ${project.status}`,
        `Timeline: ${project.startDate.toISOString().slice(0, 10)} to ${project.endDate.toISOString().slice(0, 10)} (${progressPercent}% elapsed)`,
        `Budget: ${(budgetCents / 100).toLocaleString("en-US", { style: "currency", currency: "EUR" })} | Estimated cost: ${(totalCostCents / 100).toLocaleString("en-US", { style: "currency", currency: "EUR" })} (${budgetUsedPercent}% of budget)`,
        `Staffing: ${filledDemandHeadcount}/${totalDemandHeadcount} positions filled (${staffingPercent}%)`,
        `Active assignments: ${project.assignments.filter((a) => a.status === "ACTIVE" || a.status === "CONFIRMED").length}`,
        overrunAssignments.length > 0
          ? `Timeline risk: ${overrunAssignments.length} assignment(s) extend beyond project end date`
          : "No timeline overruns detected",
      ].join("\n");

      const prompt = `Generate a concise executive summary for this project covering: budget status, staffing completeness, timeline risk, and key action items. Be specific with numbers. Keep it to 3-5 sentences.

${dataContext}`;

      const client = createAiClient(settings!);
      const model = settings!.azureOpenAiDeployment!;
      const maxTokens = settings!.aiMaxCompletionTokens ?? 300;
      const temperature = settings!.aiTemperature ?? 1;

      const provider = settings!.aiProvider ?? "openai";
      let narrative = "";
      try {
        const completion = await loggedAiCall(provider, model, prompt.length, () =>
          client.chat.completions.create({
            messages: [
              { role: "system", content: "You are a project management analyst providing brief executive summaries. Be factual and action-oriented." },
              { role: "user", content: prompt },
            ],
            max_completion_tokens: maxTokens,
            model,
            ...(temperature !== 1 ? { temperature } : {}),
          }),
        );
        narrative = completion.choices[0]?.message?.content?.trim() ?? "";
      } catch (err) {
        throw new TRPCError({
          code: "INTERNAL_SERVER_ERROR",
          message: `AI call failed: ${parseAiError(err)}`,
        });
      }

      if (!narrative) {
        throw new TRPCError({
          code: "INTERNAL_SERVER_ERROR",
          message: "AI returned an empty response.",
        });
      }

      const generatedAt = new Date().toISOString();

      // Cache in project dynamicFields
      const existingDynamic = (project.dynamicFields as Record<string, unknown>) ?? {};
      await ctx.db.project.update({
        where: { id: input.projectId },
        data: {
          dynamicFields: {
            ...existingDynamic,
            aiNarrative: narrative,
            aiNarrativeGeneratedAt: generatedAt,
          },
        },
      });

      return { narrative, generatedAt };
    }),

  /**
   * Rule-based anomaly detection across all active projects.
   * No AI involved — pure data analysis.
   */
  detectAnomalies: controllerProcedure.query(async ({ ctx }) => {
    const snapshot = await buildInsightSnapshot(ctx.db as unknown as InsightsDbAccess);
    return snapshot.anomalies;
  }),

  /**
   * Dashboard-friendly summary: anomaly counts by category + total.
   */
  getInsightsSummary: controllerProcedure.query(async ({ ctx }) => {
    const snapshot = await buildInsightSnapshot(ctx.db as unknown as InsightsDbAccess);
    return snapshot.summary;
  }),

  /**
   * Retrieve a cached AI narrative for a project (if one was previously generated).
   */
  getCachedNarrative: controllerProcedure
    .input(z.object({ projectId: z.string() }))
    .query(async ({ ctx, input }) => {
      const project = await ctx.db.project.findUnique({
        where: { id: input.projectId },
        select: { dynamicFields: true },
      });
      if (!project) {
        throw new TRPCError({ code: "NOT_FOUND", message: "Project not found" });
      }
      const df = project.dynamicFields as Record<string, unknown> | null;
      const narrative = (df?.aiNarrative as string) ?? null;
      const generatedAt = (df?.aiNarrativeGeneratedAt as string) ?? null;
      return { narrative, generatedAt };
    }),
});
