import { NextRequest, NextResponse } from "next/server";
import { getCurrentUser } from "@/lib/auth";
import { prisma } from "@/lib/prisma";

// Exercise name mapping - CSV shorthand to DB names
const NAME_MAP: Record<string, string> = {
  "Ab Wheel": "Ab Wheel Rollout",
  "BB Upright Row": "Upright Row",
  "Ball Situp": "Exercise Ball Situp",
  "Bench": "Bench Press",
  "DB Lateral Raise": "Lateral Raise",
  "Dip": "Dips (Chest)",
  "Face Pull": "Face Pulls",
  "SA Lat Pulldown": "Lat Pulldown",
  "SL Calf Raise": "Calf Raise",
  "BB Row": "Barbell Row",
  "DB Row": "Dumbbell Row",
  "GHD": "Glute ham developer",
  "Hamstring DL": "Hamstring deadlift",
  "BB Curl": "Barbell Curl",
  "BB Hip Bridge": "Hip Thrust",
  "Cable Trap": "Rear delt",
  "Chinup (Narrow)": "Chinup",
  "Chinup Negatives": "Chinup",
  "Squat (Foot Elevated)": "Squat",
  "Ball Bicep Curl": "Dumbbell Curl",
  "KB Hip Flexor": "Hip Flexor",
  "Hamstring Deadlift": "Hamstring deadlift",
  "Shoulder Press": "Overhead Press",
  "CoC": "Captains of Crush",
  "Hex DL": "Hex Bar Deadlift",
  "KB Extension": "Kettlebell Leg Extension",
  "Ski": "SkiErg",
};

interface ParsedSet {
  setNumber: number;
  weight?: number;
  weightUnit: string;
  reps?: number;
  notes?: string;
}

interface ParsedExercise {
  exerciseId: string;
  exerciseName: string;
  sets: ParsedSet[];
}

interface ParsedWorkout {
  date: string;
  exercises: ParsedExercise[];
}

interface ParseResponse {
  workouts: ParsedWorkout[];
  unmapped: string[];
}

function parseCSV(content: string): Array<Record<string, string>> {
  const lines = content.trim().split("\n");
  if (lines.length === 0) return [];

  // Parse header
  const header = lines[0].split(",").map((h) => h.trim().toLowerCase());
  const rows = [];

  // Parse data rows
  for (let i = 1; i < lines.length; i++) {
    const line = lines[i].trim();
    if (!line) continue;

    const values = line.split(",").map((v) => v.trim());
    const row: Record<string, string> = {};

    header.forEach((col, idx) => {
      if (values[idx]) {
        row[col] = values[idx];
      }
    });

    rows.push(row);
  }

  return rows;
}

function getVariationNote(originalName: string): string | null {
  if (originalName.includes("Narrow")) return "narrow";
  if (originalName.includes("Negatives")) return "negatives";
  if (originalName.includes("Foot Elevated")) return "foot elevated";
  return null;
}

function resolveExerciseName(csvName: string): string {
  // Check if it's in the name map
  if (NAME_MAP[csvName]) {
    return NAME_MAP[csvName];
  }
  // Return as-is for direct lookup
  return csvName;
}

// Parse dates like "1/27/2026" or "2026-01-27" into ISO date string
function parseDate(dateStr: string): string {
  // Try M/D/YYYY format
  const mdyMatch = dateStr.match(/^(\d{1,2})\/(\d{1,2})\/(\d{4})$/);
  if (mdyMatch) {
    const month = mdyMatch[1].padStart(2, "0");
    const day = mdyMatch[2].padStart(2, "0");
    const year = mdyMatch[3];
    return `${year}-${month}-${day}T12:00:00.000Z`;
  }
  // Try ISO format
  if (dateStr.includes("-")) {
    return new Date(dateStr + "T12:00:00.000Z").toISOString();
  }
  // Fallback
  return new Date(dateStr).toISOString();
}

export async function POST(request: NextRequest) {
  try {
    const user = await getCurrentUser();
    if (!user) {
      return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
    }

    const formData = await request.formData();
    const file = formData.get("file") as File;

    if (!file) {
      return NextResponse.json({ error: "No file provided" }, { status: 400 });
    }

    if (!file.name.endsWith(".csv")) {
      return NextResponse.json(
        { error: "File must be a CSV file" },
        { status: 400 }
      );
    }

    const content = await file.text();
    const rows = parseCSV(content);

    if (rows.length === 0) {
      return NextResponse.json(
        { error: "CSV is empty or invalid format" },
        { status: 400 }
      );
    }

    // Get all user exercises for matching
    const exercises = await prisma.exercise.findMany({
      where: { userId: user.id },
      select: { id: true, name: true },
    });

    // Build case-insensitive lookup map
    const exerciseMap = new Map<string, string>();
    for (const ex of exercises) {
      exerciseMap.set(ex.name.toLowerCase(), ex.id);
    }

    // Group rows by date
    const workoutsByDate = new Map<string, Array<Record<string, string>>>();

    const unmappedExercises = new Set<string>();

    for (const row of rows) {
      const date = row.date || row.date_str || row.workout_date || "";
      const exerciseName = row.exercise || row.exercise_name || "";

      if (!date || !exerciseName) {
        continue;
      }

      if (!workoutsByDate.has(date)) {
        workoutsByDate.set(date, []);
      }

      workoutsByDate.get(date)!.push(row);

      // Check if exercise can be resolved
      const resolvedName = resolveExerciseName(exerciseName);
      const isKnown = exerciseMap.has(resolvedName.toLowerCase());
      if (!isKnown) {
        unmappedExercises.add(exerciseName);
      }
    }

    // Build parsed workouts
    const parsedWorkouts: ParsedWorkout[] = [];

    for (const [date, rowsForDate] of workoutsByDate) {
      const exercisesMap = new Map<
        string,
        {
          exerciseId: string;
          exerciseName: string;
          sets: ParsedSet[];
        }
      >();

      for (const row of rowsForDate) {
        const csvExerciseName = row.exercise || row.exercise_name || "";
        const resolvedName = resolveExerciseName(csvExerciseName);
        const exerciseId =
          exerciseMap.get(resolvedName.toLowerCase()) || "";

        if (!exerciseId) {
          unmappedExercises.add(csvExerciseName);
          continue;
        }

        if (!exercisesMap.has(exerciseId)) {
          exercisesMap.set(exerciseId, {
            exerciseId,
            exerciseName: resolvedName,
            sets: [],
          });
        }

        const exerciseData = exercisesMap.get(exerciseId)!;
        const weight = row.weight ? parseFloat(row.weight) : undefined;
        const reps = row.reps ? parseInt(row.reps, 10) : undefined;
        let notes = row.notes || "";

        // Detect weight unit from notes
        let weightUnit = "lbs";
        if (notes.toLowerCase().includes("kg")) {
          weightUnit = "kg";
        }

        // Add variation note if applicable
        const variationNote = getVariationNote(csvExerciseName);
        if (variationNote) {
          notes = notes
            ? `${notes} (${variationNote})`
            : `(${variationNote})`;
        }

        const setNumber = exerciseData.sets.length + 1;

        exerciseData.sets.push({
          setNumber,
          weight,
          weightUnit,
          reps,
          notes: notes || undefined,
        });
      }

      const workoutExercises = Array.from(exercisesMap.values());
      if (workoutExercises.length > 0) {
        parsedWorkouts.push({
          date: parseDate(date),
          exercises: workoutExercises,
        });
      }
    }

    // Sort by date ascending (oldest first)
    parsedWorkouts.sort(
      (a, b) => new Date(a.date).getTime() - new Date(b.date).getTime()
    );

    const response: ParseResponse = {
      workouts: parsedWorkouts,
      unmapped: Array.from(unmappedExercises),
    };

    return NextResponse.json(response);
  } catch (error) {
    console.error("CSV parsing error:", error);
    return NextResponse.json(
      { error: "Failed to parse CSV file" },
      { status: 500 }
    );
  }
}