using Duempelkas.App.Services;
using Duempelkas.App.Services.Models;
using Duempelkas.Domain.Entities;
using Duempelkas.Domain.Enums;
using Duempelkas.Infrastructure.Persistence;
using Microsoft.EntityFrameworkCore;

namespace Duempelkas.Infrastructure.Services;

public class AccountService : IAccountService
{
    private readonly IDbContextFactory<FinanceDbContext> _dbFactory;

    private readonly DatabaseLocation? _location;

    public AccountService(IDbContextFactory<FinanceDbContext> dbFactory, DatabaseLocation? location = null)
    {
        _dbFactory = dbFactory;
        _location = location;
    }

    public Task<List<AccountSummaryDto>> GetAllAccountsAsync()
    {
        return GetAllAccountsAsync(null);
    }

    public async Task<List<AccountSummaryDto>> GetAllAccountsAsync(int? year)
    {
        using var lease = await DatabaseLease.AcquireAsync(_location);
        await using var db = await _dbFactory.CreateDbContextAsync();

        var accounts = await db.Accounts
            .OrderBy(a => a.Name)
            .ToListAsync();

        var entries = db.Entries.Where(e => !e.IsDeleted);

        if (year.HasValue)
        {
            var movementBeforeYearByAccountId = await entries
                .Where(e => e.Date.Year < year.Value)
                .GroupBy(e => e.AccountId)
                .ToDictionaryAsync(
                    g => g.Key,
                    g => g.Sum(e => e.Type == EntryType.Income ? e.Amount : -e.Amount));

            var movementInYearByAccountId = await entries
                .Where(e => e.Date.Year == year.Value)
                .GroupBy(e => e.AccountId)
                .ToDictionaryAsync(
                    g => g.Key,
                    g => g.Sum(e => e.Type == EntryType.Income ? e.Amount : -e.Amount));

            return accounts
                .Select(account =>
                {
                    var carryoverForYear = account.CarryoverBalance + movementBeforeYearByAccountId.GetValueOrDefault(account.Id);
                    var totalBalance = carryoverForYear + movementInYearByAccountId.GetValueOrDefault(account.Id);
                    return new AccountSummaryDto(account.Id, account.Name, carryoverForYear, totalBalance, account.CreatedUtc);
                })
                .ToList();
        }

        var movementAllByAccountId = await entries
            .GroupBy(e => e.AccountId)
            .ToDictionaryAsync(
                g => g.Key,
                g => g.Sum(e => e.Type == EntryType.Income ? e.Amount : -e.Amount));

        return accounts
            .Select(account =>
            {
                var totalBalance = account.CarryoverBalance + movementAllByAccountId.GetValueOrDefault(account.Id);
                return new AccountSummaryDto(account.Id, account.Name, account.CarryoverBalance, totalBalance, account.CreatedUtc);
            })
            .ToList();
    }

    public async Task<AccountSummaryDto> GetAccountAsync(int accountId)
    {
        using var lease = await DatabaseLease.AcquireAsync(_location);
        await using var db = await _dbFactory.CreateDbContextAsync();

        var account = await db.Accounts
            .Include(a => a.Entries)
            .FirstOrDefaultAsync(a => a.Id == accountId)
            ?? throw new InvalidOperationException($"Account {accountId} not found.");

        var totalIncome = account.Entries.Where(e => !e.IsDeleted && e.Type == EntryType.Income).Sum(e => e.Amount);
        var totalExpense = account.Entries.Where(e => !e.IsDeleted && e.Type == EntryType.Expense).Sum(e => e.Amount);
        var totalBalance = account.CarryoverBalance + totalIncome - totalExpense;

        return new AccountSummaryDto(account.Id, account.Name, account.CarryoverBalance, totalBalance, account.CreatedUtc);
    }

    public async Task<AccountSummaryDto> CreateAccountAsync(string name)
    {
        using var lease = await DatabaseLease.AcquireAsync(_location);
        await using var db = await _dbFactory.CreateDbContextAsync();

        var account = new Account { Name = name };
        db.Accounts.Add(account);
        await db.SaveChangesAsync();
        return new AccountSummaryDto(account.Id, account.Name, 0m, 0m, account.CreatedUtc);
    }

    public async Task RenameAccountAsync(int accountId, string newName)
    {
        using var lease = await DatabaseLease.AcquireAsync(_location);
        await using var db = await _dbFactory.CreateDbContextAsync();

        var account = await db.Accounts.FindAsync(accountId)
            ?? throw new InvalidOperationException($"Account {accountId} not found.");
        account.Name = newName;
        await db.SaveChangesAsync();
    }

    public async Task UpdateCarryoverAsync(int accountId, decimal carryoverBalance)
    {
        using var lease = await DatabaseLease.AcquireAsync(_location);
        await using var db = await _dbFactory.CreateDbContextAsync();

        var account = await db.Accounts.FindAsync(accountId)
            ?? throw new InvalidOperationException($"Account {accountId} not found.");
        account.CarryoverBalance = carryoverBalance;
        await db.SaveChangesAsync();
    }

    public async Task UpdateCarryoverAsync(int accountId, decimal carryoverBalance, int? year)
    {
        if (!year.HasValue)
        {
            await UpdateCarryoverAsync(accountId, carryoverBalance);
            return;
        }

        using var lease = await DatabaseLease.AcquireAsync(_location);
        await using var db = await _dbFactory.CreateDbContextAsync();

        var account = await db.Accounts.FindAsync(accountId)
            ?? throw new InvalidOperationException($"Account {accountId} not found.");

        var movementBeforeYear = await db.Entries
            .Where(e => e.AccountId == accountId && !e.IsDeleted && e.Date.Year < year.Value)
            .SumAsync(e => e.Type == EntryType.Income ? e.Amount : -e.Amount);

        account.CarryoverBalance = carryoverBalance - movementBeforeYear;
        await db.SaveChangesAsync();
    }

    public async Task DeleteAccountAsync(int accountId)
    {
        using var lease = await DatabaseLease.AcquireAsync(_location);
        await using var db = await _dbFactory.CreateDbContextAsync();

        var account = await db.Accounts
            .Include(a => a.Entries)
            .FirstOrDefaultAsync(a => a.Id == accountId)
            ?? throw new InvalidOperationException($"Account {accountId} not found.");

        var entryIds = account.Entries.Select(e => e.Id).ToList();
        var transferLinks = await db.TransferLinks
            .Where(tl => entryIds.Contains(tl.SourceEntryId) || entryIds.Contains(tl.TargetEntryId))
            .ToListAsync();

        foreach (var link in transferLinks)
        {
            var otherEntryId = entryIds.Contains(link.SourceEntryId) ? link.TargetEntryId : link.SourceEntryId;
            var otherEntry = await db.Entries.FindAsync(otherEntryId);
            if (otherEntry != null)
                db.Entries.Remove(otherEntry);
        }
        db.TransferLinks.RemoveRange(transferLinks);

        db.Accounts.Remove(account);
        await db.SaveChangesAsync();
    }

}