RealCV/src/TrueCV.Infrastructure/Services/CompanyVerifierService.cs

using FuzzySharp;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using TrueCV.Application.DTOs;
using TrueCV.Application.Helpers;
using TrueCV.Application.Interfaces;
using TrueCV.Application.Models;
using TrueCV.Domain.Entities;
using TrueCV.Infrastructure.Data;
using TrueCV.Infrastructure.ExternalApis;

namespace TrueCV.Infrastructure.Services;

public sealed class CompanyVerifierService : ICompanyVerifierService
{
    private readonly CompaniesHouseClient _companiesHouseClient;
    private readonly ApplicationDbContext _dbContext;
    private readonly ILogger<CompanyVerifierService> _logger;

    private const int FuzzyMatchThreshold = 70;
    private const int CacheExpirationDays = 30;

    public CompanyVerifierService(
        CompaniesHouseClient companiesHouseClient,
        ApplicationDbContext dbContext,
        ILogger<CompanyVerifierService> logger)
    {
        _companiesHouseClient = companiesHouseClient;
        _dbContext = dbContext;
        _logger = logger;
    }

    public async Task<CompanyVerificationResult> VerifyCompanyAsync(
        string companyName,
        DateOnly? startDate,
        DateOnly? endDate)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(companyName);

        _logger.LogDebug("Verifying company: {CompanyName}", companyName);

        // Try to find a cached match first
        var cachedMatch = await FindCachedMatchAsync(companyName);
        if (cachedMatch is not null)
        {
            _logger.LogDebug("Found cached company match for: {CompanyName}", companyName);
            return CreateVerificationResult(companyName, cachedMatch, startDate, endDate);
        }

        // Search Companies House
        try
        {
            var searchResponse = await _companiesHouseClient.SearchCompaniesAsync(companyName);

            if (searchResponse?.Items is null || searchResponse.Items.Count == 0)
            {
                _logger.LogDebug("No companies found for: {CompanyName}", companyName);
                return CreateUnverifiedResult(companyName, startDate, endDate, "No matching company found in Companies House");
            }

            // Find best fuzzy match
            var bestMatch = FindBestMatch(companyName, searchResponse.Items);

            if (bestMatch is null)
            {
                _logger.LogDebug("No fuzzy match above threshold for: {CompanyName}", companyName);
                return CreateUnverifiedResult(companyName, startDate, endDate,
                    $"No company name matched above {FuzzyMatchThreshold}% threshold");
            }

            // Cache the matched company
            var match = bestMatch.Value;
            await CacheCompanyAsync(match.Item);

            _logger.LogInformation(
                "Verified company {ClaimedName} matched to {MatchedName} with score {Score}%",
                companyName, match.Item.Title, match.Score);

            return new CompanyVerificationResult
            {
                ClaimedCompany = companyName,
                MatchedCompanyName = match.Item.Title,
                MatchedCompanyNumber = match.Item.CompanyNumber,
                MatchScore = match.Score,
                IsVerified = true,
                VerificationNotes = $"Matched with {match.Score}% confidence",
                ClaimedStartDate = startDate,
                ClaimedEndDate = endDate
            };
        }
        catch (CompaniesHouseRateLimitException ex)
        {
            _logger.LogWarning(ex, "Rate limit hit while verifying company: {CompanyName}", companyName);
            return CreateUnverifiedResult(companyName, startDate, endDate,
                "Verification temporarily unavailable due to rate limiting");
        }
    }

    public async Task<List<CompanySearchResult>> SearchCompaniesAsync(string query)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(query);

        _logger.LogDebug("Searching companies for query: {Query}", query);

        var response = await _companiesHouseClient.SearchCompaniesAsync(query);

        if (response?.Items is null)
        {
            return [];
        }

        return response.Items.Select(item => new CompanySearchResult
        {
            CompanyNumber = item.CompanyNumber,
            CompanyName = item.Title,
            CompanyStatus = item.CompanyStatus ?? "Unknown",
            IncorporationDate = DateHelpers.ParseDate(item.DateOfCreation),
            AddressSnippet = item.AddressSnippet
        }).ToList();
    }

    private async Task<CompanyCache?> FindCachedMatchAsync(string companyName)
    {
        var cutoffDate = DateTime.UtcNow.AddDays(-CacheExpirationDays);

        // Get recent cached companies
        var cachedCompanies = await _dbContext.CompanyCache
            .Where(c => c.CachedAt >= cutoffDate)
            .ToListAsync();

        if (cachedCompanies.Count == 0)
        {
            return null;
        }

        // Find best fuzzy match in cache
        var matches = cachedCompanies
            .Select(c => new { Company = c, Score = Fuzz.Ratio(companyName.ToUpperInvariant(), c.CompanyName.ToUpperInvariant()) })
            .Where(m => m.Score >= FuzzyMatchThreshold)
            .OrderByDescending(m => m.Score)
            .FirstOrDefault();

        return matches?.Company;
    }

    private static (CompaniesHouseSearchItem Item, int Score)? FindBestMatch(
        string companyName,
        List<CompaniesHouseSearchItem> items)
    {
        var normalizedSearch = companyName.ToUpperInvariant();

        var matches = items
            .Select(item => (Item: item, Score: Fuzz.Ratio(normalizedSearch, item.Title.ToUpperInvariant())))
            .Where(m => m.Score >= FuzzyMatchThreshold)
            .OrderByDescending(m => m.Score)
            .ToList();

        return matches.Count > 0 ? matches[0] : null;
    }

    private async Task CacheCompanyAsync(CompaniesHouseSearchItem item)
    {
        var existingCache = await _dbContext.CompanyCache
            .FirstOrDefaultAsync(c => c.CompanyNumber == item.CompanyNumber);

        if (existingCache is not null)
        {
            existingCache.CompanyName = item.Title;
            existingCache.Status = item.CompanyStatus ?? "Unknown";
            existingCache.IncorporationDate = DateHelpers.ParseDate(item.DateOfCreation);
            existingCache.DissolutionDate = DateHelpers.ParseDate(item.DateOfCessation);
            existingCache.CachedAt = DateTime.UtcNow;
        }
        else
        {
            var cacheEntry = new CompanyCache
            {
                CompanyNumber = item.CompanyNumber,
                CompanyName = item.Title,
                Status = item.CompanyStatus ?? "Unknown",
                IncorporationDate = DateHelpers.ParseDate(item.DateOfCreation),
                DissolutionDate = DateHelpers.ParseDate(item.DateOfCessation),
                CachedAt = DateTime.UtcNow
            };

            _dbContext.CompanyCache.Add(cacheEntry);
        }

        await _dbContext.SaveChangesAsync();
    }

    private static CompanyVerificationResult CreateVerificationResult(
        string claimedCompany,
        CompanyCache cached,
        DateOnly? startDate,
        DateOnly? endDate)
    {
        var matchScore = Fuzz.Ratio(
            claimedCompany.ToUpperInvariant(),
            cached.CompanyName.ToUpperInvariant());

        return new CompanyVerificationResult
        {
            ClaimedCompany = claimedCompany,
            MatchedCompanyName = cached.CompanyName,
            MatchedCompanyNumber = cached.CompanyNumber,
            MatchScore = matchScore,
            IsVerified = true,
            VerificationNotes = $"Matched from cache with {matchScore}% confidence",
            ClaimedStartDate = startDate,
            ClaimedEndDate = endDate
        };
    }

    private static CompanyVerificationResult CreateUnverifiedResult(
        string companyName,
        DateOnly? startDate,
        DateOnly? endDate,
        string reason)
    {
        return new CompanyVerificationResult
        {
            ClaimedCompany = companyName,
            MatchedCompanyName = null,
            MatchedCompanyNumber = null,
            MatchScore = 0,
            IsVerified = false,
            VerificationNotes = reason,
            ClaimedStartDate = startDate,
            ClaimedEndDate = endDate
        };
    }

}