refactor: Phase 7-3 - Clients + TaxFilings API-First (WIP)

**Clients Migration Complete:**
- ClientController: GET /api/client (paged), POST/PUT/DELETE
- ClientBrowserClient: IClientBrowserClient interface + implementation
- ClientList.razor: Service → API client
- ClientEdit.razor: Service → API client (Create/Update)

**TaxFilings API Framework Ready:**
- TaxFilingController: GET upcoming, GET by client, POST/PUT/DELETE
- TaxFilingBrowserClient: ITaxFilingBrowserClient interface + impl
- Registered in Program.cs with TokenRefreshHandler

**SOLID Applied:**
✓ Separation of concerns (Controller → Service → Repository)
✓ Dependency inversion (Blazor → Browser clients, not services)
✓ Interface segregation (Specialized clients per domain)

**Status:**
- Clients Blazor: ✅ ClientList + ClientEdit refactored
- TaxFilings Blazor: ⏳ Pending refactor (pages exist)
- Faqs: ⏳ API + Blazor pending
- Announcements: ⏳ API + Blazor pending
- Phase 6 SignalR: ⏳ Deferred

Next: Refactor TaxFilings Blazor pages, then Faqs & Announcements
Build: ✅ Success (0 errors, 2 warnings in Dashboard)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

TaxBaik.Web/Components/Admin/Pages/Clients/ClientEdit.razor

@@ -2,9 +2,9 @@
 @page "/admin/clients/{Id:int}/edit"
 @attribute [Authorize]
 @using TaxBaik.Application.DTOs
-@using TaxBaik.Application.Services
+@using TaxBaik.Web.Services
 @using TaxBaik.Domain.Entities
-@inject ClientService ClientService
+@inject IClientBrowserClient ClientClient
 @inject NavigationManager Navigation
 @inject ISnackbar Snackbar
 
@@ -124,25 +124,34 @@
     {
         if (Id.HasValue)
         {
-            var client = await ClientService.GetByIdAsync(Id.Value);
-            if (client is null)
+            try
             {
-                Snackbar.Add("고객을 찾을 수 없습니다.", Severity.Error);
+                var client = await ClientClient.GetByIdAsync(Id.Value);
+                if (client is null)
+                {
+                    Snackbar.Add("고객을 찾을 수 없습니다.", Severity.Error);
+                    Navigation.NavigateTo("/taxbaik/admin/clients");
+                    return;
+                }
+                dto = new CreateClientDto
+                {
+                    Name = client.Name,
+                    CompanyName = client.CompanyName,
+                    Phone = client.Phone,
+                    Email = client.Email,
+                    ServiceType = client.ServiceType,
+                    TaxType = client.TaxType,
+                    Status = client.Status,
+                    Source = client.Source,
+                    Memo = client.Memo
+                };
+            }
+            catch (Exception ex)
+            {
+                Snackbar.Add($"오류: {ex.Message}", Severity.Error);
                 Navigation.NavigateTo("/taxbaik/admin/clients");
                 return;
             }
-            dto = new CreateClientDto
-            {
-                Name = client.Name,
-                CompanyName = client.CompanyName,
-                Phone = client.Phone,
-                Email = client.Email,
-                ServiceType = client.ServiceType,
-                TaxType = client.TaxType,
-                Status = client.Status,
-                Source = client.Source,
-                Memo = client.Memo
-            };
         }
         isLoading = false;
     }
@@ -157,13 +166,19 @@
         {
             if (Id.HasValue)
             {
-                await ClientService.UpdateAsync(Id.Value, dto);
-                Snackbar.Add("고객 정보가 수정되었습니다.", Severity.Success);
+                var result = await ClientClient.UpdateAsync(Id.Value, dto);
+                if (result != null)
+                    Snackbar.Add("고객 정보가 수정되었습니다.", Severity.Success);
+                else
+                    Snackbar.Add("수정에 실패했습니다.", Severity.Error);
             }
             else
             {
-                var newId = await ClientService.CreateAsync(dto);
-                Snackbar.Add("고객이 등록되었습니다.", Severity.Success);
+                var result = await ClientClient.CreateAsync(dto);
+                if (result != null)
+                    Snackbar.Add("고객이 등록되었습니다.", Severity.Success);
+                else
+                    Snackbar.Add("등록에 실패했습니다.", Severity.Error);
             }
             Navigation.NavigateTo("/taxbaik/admin/clients");
         }

TaxBaik.Web/Components/Admin/Pages/Clients/ClientList.razor

@@ -1,8 +1,8 @@
 @page "/admin/clients"
 @attribute [Authorize]
-@using TaxBaik.Application.Services
+@using TaxBaik.Web.Services
 @using TaxBaik.Domain.Entities
-@inject ClientService ClientService
+@inject IClientBrowserClient ClientClient
 @inject NavigationManager Navigation
 @inject IDialogService DialogService
 @inject ISnackbar Snackbar
@@ -141,14 +141,24 @@
 
     private async Task LoadAsync()
     {
-        var (items, total) = await ClientService.GetPagedAsync(
-            currentPage, PageSize,
-            string.IsNullOrEmpty(statusFilter) ? null : statusFilter,
-            string.IsNullOrEmpty(searchText) ? null : searchText);
+        try
+        {
+            var (items, total) = await ClientClient.GetPagedAsync(
+                currentPage, PageSize,
+                string.IsNullOrEmpty(statusFilter) ? null : statusFilter,
+                string.IsNullOrEmpty(searchText) ? null : searchText);
 
-        clients = items.ToList();
-        totalCount = total;
-        totalPages = (int)Math.Ceiling((double)total / PageSize);
+            clients = items.ToList();
+            totalCount = total;
+            totalPages = (int)Math.Ceiling((double)total / PageSize);
+        }
+        catch (Exception ex)
+        {
+            Snackbar.Add($"오류: {ex.Message}", Severity.Error);
+            clients = [];
+            totalCount = 0;
+            totalPages = 0;
+        }
     }
 
     private async Task SearchAsync()
@@ -185,8 +195,23 @@
 
         if (confirmed != true) return;
 
-        await ClientService.DeleteAsync(client.Id);
-        Snackbar.Add($"{client.Name} 고객이 삭제되었습니다.", Severity.Success);
+        try
+        {
+            var success = await ClientClient.DeleteAsync(client.Id);
+            if (success)
+            {
+                Snackbar.Add($"{client.Name} 고객이 삭제되었습니다.", Severity.Success);
+                await LoadAsync();
+            }
+            else
+            {
+                Snackbar.Add("삭제에 실패했습니다.", Severity.Error);
+            }
+        }
+        catch (Exception ex)
+        {
+            Snackbar.Add($"오류: {ex.Message}", Severity.Error);
+        }
         await LoadAsync();
     }
 }

TaxBaik.Web/Controllers/ClientController.cs

@@ -0,0 +1,80 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using TaxBaik.Application.DTOs;
+using TaxBaik.Application.Services;
+
+namespace TaxBaik.Web.Controllers;
+
+[ApiController]
+[Route("api/[controller]")]
+[Authorize]
+public class ClientController : ControllerBase
+{
+    private readonly ClientService _clientService;
+
+    public ClientController(ClientService clientService)
+    {
+        _clientService = clientService;
+    }
+
+    [HttpGet]
+    public async Task<IActionResult> GetPaged(
+        [FromQuery] int page = 1,
+        [FromQuery] int pageSize = 20,
+        [FromQuery] string? status = null,
+        [FromQuery] string? search = null)
+    {
+        var (clients, total) = await _clientService.GetPagedAsync(page, pageSize, status, search);
+        return Ok(new { data = clients, total, page, pageSize });
+    }
+
+    [HttpGet("{id}")]
+    public async Task<IActionResult> GetById(int id)
+    {
+        var client = await _clientService.GetByIdAsync(id);
+        if (client == null)
+            return NotFound(new ProblemDetails { Title = "고객을 찾을 수 없습니다.", Status = StatusCodes.Status404NotFound });
+
+        return Ok(client);
+    }
+
+    [HttpPost]
+    public async Task<IActionResult> Create([FromBody] CreateClientDto dto)
+    {
+        try
+        {
+            var clientId = await _clientService.CreateAsync(dto);
+            var client = await _clientService.GetByIdAsync(clientId);
+            return CreatedAtAction(nameof(GetById), new { id = clientId }, client);
+        }
+        catch (ValidationException ex)
+        {
+            return BadRequest(new ProblemDetails { Title = ex.Message, Status = StatusCodes.Status400BadRequest });
+        }
+    }
+
+    [HttpPut("{id}")]
+    public async Task<IActionResult> Update(int id, [FromBody] CreateClientDto dto)
+    {
+        try
+        {
+            await _clientService.UpdateAsync(id, dto);
+            var client = await _clientService.GetByIdAsync(id);
+            if (client == null)
+                return NotFound(new ProblemDetails { Title = "고객을 찾을 수 없습니다.", Status = StatusCodes.Status404NotFound });
+
+            return Ok(client);
+        }
+        catch (ValidationException ex)
+        {
+            return BadRequest(new ProblemDetails { Title = ex.Message, Status = StatusCodes.Status400BadRequest });
+        }
+    }
+
+    [HttpDelete("{id}")]
+    public async Task<IActionResult> Delete(int id)
+    {
+        await _clientService.DeleteAsync(id);
+        return NoContent();
+    }
+}

TaxBaik.Web/Controllers/TaxFilingController.cs

@@ -0,0 +1,84 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using TaxBaik.Application.Services;
+using TaxBaik.Domain.Entities;
+
+namespace TaxBaik.Web.Controllers;
+
+[ApiController]
+[Route("api/[controller]")]
+[Authorize]
+public class TaxFilingController : ControllerBase
+{
+    private readonly TaxFilingService _taxFilingService;
+
+    public TaxFilingController(TaxFilingService taxFilingService)
+    {
+        _taxFilingService = taxFilingService;
+    }
+
+    [HttpGet("upcoming")]
+    public async Task<IActionResult> GetUpcoming([FromQuery] int daysAhead = 30)
+    {
+        var filings = await _taxFilingService.GetUpcomingAsync(daysAhead);
+        return Ok(new { data = filings });
+    }
+
+    [HttpGet("client/{clientId}")]
+    public async Task<IActionResult> GetByClientId(int clientId)
+    {
+        var filings = await _taxFilingService.GetByClientIdAsync(clientId);
+        return Ok(new { data = filings });
+    }
+
+    [HttpGet("{id}")]
+    public async Task<IActionResult> GetById(int id)
+    {
+        var filing = await _taxFilingService.GetByIdAsync(id);
+        if (filing == null)
+            return NotFound(new ProblemDetails { Title = "신고 일정을 찾을 수 없습니다.", Status = StatusCodes.Status404NotFound });
+
+        return Ok(filing);
+    }
+
+    [HttpPost]
+    public async Task<IActionResult> Create([FromBody] TaxFiling filing)
+    {
+        try
+        {
+            var filingId = await _taxFilingService.CreateAsync(filing);
+            var result = await _taxFilingService.GetByIdAsync(filingId);
+            return CreatedAtAction(nameof(GetById), new { id = filingId }, result);
+        }
+        catch (Exception ex)
+        {
+            return BadRequest(new ProblemDetails { Title = ex.Message, Status = StatusCodes.Status400BadRequest });
+        }
+    }
+
+    [HttpPut("{id}")]
+    public async Task<IActionResult> Update(int id, [FromBody] TaxFiling filing)
+    {
+        filing.Id = id;
+        try
+        {
+            await _taxFilingService.UpdateAsync(filing);
+            var result = await _taxFilingService.GetByIdAsync(id);
+            if (result == null)
+                return NotFound(new ProblemDetails { Title = "신고 일정을 찾을 수 없습니다.", Status = StatusCodes.Status404NotFound });
+
+            return Ok(result);
+        }
+        catch (Exception ex)
+        {
+            return BadRequest(new ProblemDetails { Title = ex.Message, Status = StatusCodes.Status400BadRequest });
+        }
+    }
+
+    [HttpDelete("{id}")]
+    public async Task<IActionResult> Delete(int id)
+    {
+        await _taxFilingService.DeleteAsync(id);
+        return NoContent();
+    }
+}

TaxBaik.Web/Program.cs

@@ -76,6 +76,16 @@ builder.Services.AddHttpClient<IAdminDashboardClient, AdminDashboardClient>(clie
 })
     .AddHttpMessageHandler<TokenRefreshHandler>();
 builder.Services.AddHttpClient<IInquiryBrowserClient, InquiryBrowserClient>(client =>
+{
+    client.BaseAddress = new Uri("http://localhost:5001/taxbaik/api/");
+})
+    .AddHttpMessageHandler<TokenRefreshHandler>();
+builder.Services.AddHttpClient<IClientBrowserClient, ClientBrowserClient>(client =>
+{
+    client.BaseAddress = new Uri("http://localhost:5001/taxbaik/api/");
+})
+    .AddHttpMessageHandler<TokenRefreshHandler>();
+builder.Services.AddHttpClient<ITaxFilingBrowserClient, TaxFilingBrowserClient>(client =>
 {
     client.BaseAddress = new Uri("http://localhost:5001/taxbaik/api/");
 })

TaxBaik.Web/Services/ClientBrowserClient.cs

@@ -0,0 +1,125 @@
+namespace TaxBaik.Web.Services;
+
+using System.Net.Http.Json;
+using TaxBaik.Application.DTOs;
+using TaxBaik.Domain.Entities;
+
+/// <summary>
+/// Client API Client for Admin Blazor
+/// SOLID: Single Responsibility - Client API calls only
+/// </summary>
+public interface IClientBrowserClient
+{
+    Task<(IEnumerable<Client> Items, int Total)> GetPagedAsync(
+        int page = 1, int pageSize = 20, string? status = null, string? search = null, CancellationToken ct = default);
+    Task<Client?> GetByIdAsync(int id, CancellationToken ct = default);
+    Task<Client?> CreateAsync(CreateClientDto dto, CancellationToken ct = default);
+    Task<Client?> UpdateAsync(int id, CreateClientDto dto, CancellationToken ct = default);
+    Task<bool> DeleteAsync(int id, CancellationToken ct = default);
+}
+
+public class ClientBrowserClient : IClientBrowserClient
+{
+    private readonly HttpClient _http;
+    private readonly ILogger<ClientBrowserClient> _logger;
+
+    public ClientBrowserClient(HttpClient http, ILogger<ClientBrowserClient> logger)
+    {
+        _http = http;
+        _logger = logger;
+    }
+
+    public async Task<(IEnumerable<Client> Items, int Total)> GetPagedAsync(
+        int page = 1, int pageSize = 20, string? status = null, string? search = null, CancellationToken ct = default)
+    {
+        try
+        {
+            var query = $"client?page={page}&pageSize={pageSize}";
+            if (!string.IsNullOrEmpty(status))
+                query += $"&status={status}";
+            if (!string.IsNullOrEmpty(search))
+                query += $"&search={Uri.EscapeDataString(search)}";
+
+            var result = await _http.GetFromJsonAsync<ClientPagedResponse>(query, cancellationToken: ct);
+            return result != null ? (result.Data, result.Total) : ([], 0);
+        }
+        catch (HttpRequestException ex)
+        {
+            _logger.LogError(ex, "Failed to fetch clients");
+            throw;
+        }
+    }
+
+    public async Task<Client?> GetByIdAsync(int id, CancellationToken ct = default)
+    {
+        try
+        {
+            return await _http.GetFromJsonAsync<Client>($"client/{id}", cancellationToken: ct);
+        }
+        catch (HttpRequestException ex)
+        {
+            _logger.LogError(ex, "Failed to fetch client {ClientId}", id);
+            throw;
+        }
+    }
+
+    public async Task<Client?> CreateAsync(CreateClientDto dto, CancellationToken ct = default)
+    {
+        try
+        {
+            var response = await _http.PostAsJsonAsync("client", dto, cancellationToken: ct);
+            if (!response.IsSuccessStatusCode)
+                return null;
+
+            var content = await response.Content.ReadAsStringAsync(ct);
+            return System.Text.Json.JsonSerializer.Deserialize<Client>(
+                content,
+                new System.Text.Json.JsonSerializerOptions { PropertyNameCaseInsensitive = true });
+        }
+        catch (HttpRequestException ex)
+        {
+            _logger.LogError(ex, "Failed to create client");
+            throw;
+        }
+    }
+
+    public async Task<Client?> UpdateAsync(int id, CreateClientDto dto, CancellationToken ct = default)
+    {
+        try
+        {
+            var response = await _http.PutAsJsonAsync($"client/{id}", dto, cancellationToken: ct);
+            if (!response.IsSuccessStatusCode)
+                return null;
+
+            var content = await response.Content.ReadAsStringAsync(ct);
+            return System.Text.Json.JsonSerializer.Deserialize<Client>(
+                content,
+                new System.Text.Json.JsonSerializerOptions { PropertyNameCaseInsensitive = true });
+        }
+        catch (HttpRequestException ex)
+        {
+            _logger.LogError(ex, "Failed to update client {ClientId}", id);
+            throw;
+        }
+    }
+
+    public async Task<bool> DeleteAsync(int id, CancellationToken ct = default)
+    {
+        try
+        {
+            var response = await _http.DeleteAsync($"client/{id}", cancellationToken: ct);
+            return response.IsSuccessStatusCode;
+        }
+        catch (HttpRequestException ex)
+        {
+            _logger.LogError(ex, "Failed to delete client {ClientId}", id);
+            throw;
+        }
+    }
+
+    private class ClientPagedResponse
+    {
+        public List<Client> Data { get; set; } = [];
+        public int Total { get; set; }
+    }
+}

TaxBaik.Web/Services/TaxFilingBrowserClient.cs

@@ -0,0 +1,132 @@
+namespace TaxBaik.Web.Services;
+
+using System.Net.Http.Json;
+using TaxBaik.Domain.Entities;
+
+/// <summary>
+/// TaxFiling API Client for Admin Blazor
+/// </summary>
+public interface ITaxFilingBrowserClient
+{
+    Task<IEnumerable<TaxFiling>> GetUpcomingAsync(int daysAhead = 30, CancellationToken ct = default);
+    Task<IEnumerable<TaxFiling>> GetByClientIdAsync(int clientId, CancellationToken ct = default);
+    Task<TaxFiling?> GetByIdAsync(int id, CancellationToken ct = default);
+    Task<TaxFiling?> CreateAsync(TaxFiling filing, CancellationToken ct = default);
+    Task<TaxFiling?> UpdateAsync(int id, TaxFiling filing, CancellationToken ct = default);
+    Task<bool> DeleteAsync(int id, CancellationToken ct = default);
+}
+
+public class TaxFilingBrowserClient : ITaxFilingBrowserClient
+{
+    private readonly HttpClient _http;
+    private readonly ILogger<TaxFilingBrowserClient> _logger;
+
+    public TaxFilingBrowserClient(HttpClient http, ILogger<TaxFilingBrowserClient> logger)
+    {
+        _http = http;
+        _logger = logger;
+    }
+
+    public async Task<IEnumerable<TaxFiling>> GetUpcomingAsync(int daysAhead = 30, CancellationToken ct = default)
+    {
+        try
+        {
+            var result = await _http.GetFromJsonAsync<TaxFilingListResponse>(
+                $"tax-filing/upcoming?daysAhead={daysAhead}", cancellationToken: ct);
+            return result?.Data ?? [];
+        }
+        catch (HttpRequestException ex)
+        {
+            _logger.LogError(ex, "Failed to fetch upcoming filings");
+            throw;
+        }
+    }
+
+    public async Task<IEnumerable<TaxFiling>> GetByClientIdAsync(int clientId, CancellationToken ct = default)
+    {
+        try
+        {
+            var result = await _http.GetFromJsonAsync<TaxFilingListResponse>(
+                $"tax-filing/client/{clientId}", cancellationToken: ct);
+            return result?.Data ?? [];
+        }
+        catch (HttpRequestException ex)
+        {
+            _logger.LogError(ex, "Failed to fetch filings for client {ClientId}", clientId);
+            throw;
+        }
+    }
+
+    public async Task<TaxFiling?> GetByIdAsync(int id, CancellationToken ct = default)
+    {
+        try
+        {
+            return await _http.GetFromJsonAsync<TaxFiling>(
+                $"tax-filing/{id}", cancellationToken: ct);
+        }
+        catch (HttpRequestException ex)
+        {
+            _logger.LogError(ex, "Failed to fetch filing {FilingId}", id);
+            throw;
+        }
+    }
+
+    public async Task<TaxFiling?> CreateAsync(TaxFiling filing, CancellationToken ct = default)
+    {
+        try
+        {
+            var response = await _http.PostAsJsonAsync("tax-filing", filing, cancellationToken: ct);
+            if (!response.IsSuccessStatusCode)
+                return null;
+
+            var content = await response.Content.ReadAsStringAsync(ct);
+            return System.Text.Json.JsonSerializer.Deserialize<TaxFiling>(
+                content,
+                new System.Text.Json.JsonSerializerOptions { PropertyNameCaseInsensitive = true });
+        }
+        catch (HttpRequestException ex)
+        {
+            _logger.LogError(ex, "Failed to create filing");
+            throw;
+        }
+    }
+
+    public async Task<TaxFiling?> UpdateAsync(int id, TaxFiling filing, CancellationToken ct = default)
+    {
+        try
+        {
+            var response = await _http.PutAsJsonAsync($"tax-filing/{id}", filing, cancellationToken: ct);
+            if (!response.IsSuccessStatusCode)
+                return null;
+
+            var content = await response.Content.ReadAsStringAsync(ct);
+            return System.Text.Json.JsonSerializer.Deserialize<TaxFiling>(
+                content,
+                new System.Text.Json.JsonSerializerOptions { PropertyNameCaseInsensitive = true });
+        }
+        catch (HttpRequestException ex)
+        {
+            _logger.LogError(ex, "Failed to update filing {FilingId}", id);
+            throw;
+        }
+    }
+
+    public async Task<bool> DeleteAsync(int id, CancellationToken ct = default)
+    {
+        try
+        {
+            var response = await _http.DeleteAsync($"tax-filing/{id}", cancellationToken: ct);
+            return response.IsSuccessStatusCode;
+        }
+        catch (HttpRequestException ex)
+        {
+            _logger.LogError(ex, "Failed to delete filing {FilingId}", id);
+            throw;
+        }
+    }
+
+    private class TaxFilingListResponse
+    {
+        public List<TaxFiling> Data { get; set; } = [];
+    }
+}