using Microsoft.EntityFrameworkCore;
using Tiku.Application.Catalog;
using Tiku.Domain.Catalog;
using Tiku.Infrastructure.Persistence;

namespace Tiku.Infrastructure.Catalog;

public sealed class CatalogQueryService(TikuDbContext dbContext) : ICatalogQueryService
{
    private const int DefaultLimit = 500;
    private const int MaxLimit = 2000;

    public async Task<CatalogList<RegionCatalogItem>> GetRegionsAsync(
        CatalogFilter filter,
        CancellationToken cancellationToken = default)
    {
        var query = dbContext.Regions
            .AsNoTracking()
            .Where(region =>
                region.TenantId == filter.TenantId &&
                region.IsActive);

        query = ApplyKeyword(query, filter.Keyword);

        var items = await query
            .OrderBy(region => region.SortOrder)
            .ThenBy(region => region.Name)
            .ThenBy(region => region.CreatedAt)
            .Take(ResolveLimit(filter.Limit))
            .Select(region => new RegionCatalogItem(
                region.Id,
                region.LegacyId,
                region.Name,
                region.Code,
                region.ShortName,
                region.FullName,
                region.Icon,
                region.Pinyin,
                region.SortOrder,
                region.IsHot))
            .ToArrayAsync(cancellationToken);

        return new CatalogList<RegionCatalogItem>(items);
    }

    public async Task<CatalogList<RegionModuleCatalogItem>> GetRegionModulesAsync(
        CatalogFilter filter,
        CancellationToken cancellationToken = default)
    {
        var query = dbContext.RegionModules
            .AsNoTracking()
            .Where(module =>
                module.TenantId == filter.TenantId &&
                module.IsActive);

        if (filter.RegionId.HasValue)
        {
            query = query.Where(module => module.RegionId == filter.RegionId.Value);
        }

        query = ApplyKeyword(query, filter.Keyword);

        var items = await query
            .OrderBy(module => module.SortOrder)
            .ThenBy(module => module.Name)
            .ThenBy(module => module.CreatedAt)
            .Take(ResolveLimit(filter.Limit))
            .Select(module => new RegionModuleCatalogItem(
                module.Id,
                module.LegacyId,
                module.RegionId,
                module.Name,
                module.Type,
                module.Icon,
                module.Color,
                module.TextColor,
                module.Description,
                module.Route,
                module.SortOrder,
                module.IsPrimarySchoolModule))
            .ToArrayAsync(cancellationToken);

        return new CatalogList<RegionModuleCatalogItem>(items);
    }

    public async Task<CatalogList<ModuleNodeCatalogItem>> GetModuleNodesAsync(
        CatalogFilter filter,
        CancellationToken cancellationToken = default)
    {
        var query = dbContext.ModuleNodes
            .AsNoTracking()
            .Where(node =>
                node.TenantId == filter.TenantId &&
                node.IsActive);

        if (filter.RegionId.HasValue)
        {
            query = query.Where(node => node.RegionId == filter.RegionId.Value);
        }

        if (filter.ModuleId.HasValue)
        {
            query = query.Where(node => node.ModuleId == filter.ModuleId.Value);
        }

        if (filter.ParentIsRoot)
        {
            query = query.Where(node => node.ParentId == null);
        }
        else if (filter.ParentId.HasValue)
        {
            query = query.Where(node => node.ParentId == filter.ParentId.Value);
        }

        if (TryParseModuleNodeType(filter.Type, out var nodeType))
        {
            query = query.Where(node => node.Type == nodeType);
        }

        query = ApplyKeyword(query, filter.Keyword);

        var items = await query
            .OrderBy(node => node.SortOrder)
            .ThenBy(node => node.Name)
            .ThenBy(node => node.CreatedAt)
            .Take(ResolveLimit(filter.Limit))
            .Select(node => new ModuleNodeCatalogItem(
                node.Id,
                node.LegacyId,
                node.RegionId,
                node.ModuleId,
                node.ParentId,
                node.LegacyParentId,
                node.Type,
                node.Name,
                node.Path,
                node.SortOrder,
                node.Metadata))
            .ToArrayAsync(cancellationToken);

        return new CatalogList<ModuleNodeCatalogItem>(items);
    }

    public async Task<CatalogList<SchoolCatalogItem>> GetSchoolsAsync(
        CatalogFilter filter,
        CancellationToken cancellationToken = default)
    {
        var query = dbContext.Schools
            .AsNoTracking()
            .Where(school => school.TenantId == filter.TenantId);

        if (filter.RegionId.HasValue)
        {
            query = query.Where(school => school.RegionId == filter.RegionId.Value);
        }

        if (filter.ModuleId.HasValue)
        {
            query = query.Where(school => school.ModuleId == filter.ModuleId.Value);
        }

        query = ApplyKeyword(query, filter.Keyword);

        var items = await query
            .OrderBy(school => school.Name)
            .ThenBy(school => school.CreatedAt)
            .Take(ResolveLimit(filter.Limit))
            .Select(school => new SchoolCatalogItem(
                school.Id,
                school.LegacyId,
                school.RegionId,
                school.ModuleId,
                school.Name,
                school.ProfessionalExamDate,
                school.Metadata))
            .ToArrayAsync(cancellationToken);

        return new CatalogList<SchoolCatalogItem>(items);
    }

    public async Task<CatalogList<MajorCatalogItem>> GetMajorsAsync(
        CatalogFilter filter,
        CancellationToken cancellationToken = default)
    {
        var query = dbContext.Majors
            .AsNoTracking()
            .Where(major =>
                major.TenantId == filter.TenantId &&
                major.IsActive);

        if (filter.RegionId.HasValue)
        {
            query = query.Where(major => major.RegionId == filter.RegionId.Value);
        }

        if (filter.SchoolId.HasValue)
        {
            query = query.Where(major => major.SchoolId == filter.SchoolId.Value);
        }

        query = ApplyKeyword(query, filter.Keyword);

        var items = await query
            .OrderBy(major => major.SortOrder)
            .ThenBy(major => major.Name)
            .ThenBy(major => major.CreatedAt)
            .Take(ResolveLimit(filter.Limit))
            .Select(major => new MajorCatalogItem(
                major.Id,
                major.LegacyId,
                major.RegionId,
                major.SchoolId,
                major.Name,
                major.Description,
                major.StudyTips,
                major.SortOrder))
            .ToArrayAsync(cancellationToken);

        return new CatalogList<MajorCatalogItem>(items);
    }

    public async Task<CatalogList<SubjectCatalogItem>> GetSubjectsAsync(
        CatalogFilter filter,
        CancellationToken cancellationToken = default)
    {
        var query = dbContext.Subjects
            .AsNoTracking()
            .Where(subject =>
                subject.TenantId == filter.TenantId &&
                subject.IsActive);

        if (filter.RegionId.HasValue)
        {
            query = query.Where(subject => subject.RegionId == filter.RegionId.Value);
        }

        if (filter.SchoolId.HasValue)
        {
            query = query.Where(subject => subject.SchoolId == filter.SchoolId.Value);
        }

        if (filter.MajorId.HasValue)
        {
            query = query.Where(subject => subject.MajorId == filter.MajorId.Value);
        }

        if (filter.ModuleId.HasValue)
        {
            query = query.Where(subject => subject.ModuleId == filter.ModuleId.Value);
        }

        if (TryParseSubjectType(filter.Type, out var subjectType))
        {
            query = query.Where(subject => subject.Type == subjectType);
        }

        query = ApplyKeyword(query, filter.Keyword);

        var items = await query
            .OrderBy(subject => subject.SortOrder)
            .ThenBy(subject => subject.Name)
            .ThenBy(subject => subject.CreatedAt)
            .Take(ResolveLimit(filter.Limit))
            .Select(subject => new SubjectCatalogItem(
                subject.Id,
                subject.LegacyId,
                subject.RegionId,
                subject.ModuleId,
                subject.SchoolId,
                subject.MajorId,
                subject.NodeId,
                subject.Name,
                subject.Type,
                subject.Icon,
                subject.Description,
                subject.Stats,
                subject.SortOrder))
            .ToArrayAsync(cancellationToken);

        return new CatalogList<SubjectCatalogItem>(items);
    }

    public async Task<CatalogList<CategoryCatalogItem>> GetCategoriesAsync(
        CatalogFilter filter,
        CancellationToken cancellationToken = default)
    {
        var query = dbContext.Categories
            .AsNoTracking()
            .Where(category =>
                category.TenantId == filter.TenantId &&
                category.IsActive);

        if (filter.SubjectId.HasValue)
        {
            query = query.Where(category => category.SubjectId == filter.SubjectId.Value);
        }

        if (filter.NodeId.HasValue)
        {
            query = query.Where(category => category.NodeId == filter.NodeId.Value);
        }

        if (TryParseCategoryType(filter.Type, out var categoryType))
        {
            query = query.Where(category => category.CategoryType == categoryType);
        }

        query = ApplyKeyword(query, filter.Keyword);

        var items = await query
            .OrderBy(category => category.SortOrder)
            .ThenBy(category => category.Name)
            .ThenBy(category => category.CreatedAt)
            .Take(ResolveLimit(filter.Limit))
            .Select(category => new CategoryCatalogItem(
                category.Id,
                category.LegacyId,
                category.SubjectId,
                category.NodeId,
                category.Name,
                category.CategoryType,
                category.SortOrder,
                category.SvipQuestionLimit))
            .ToArrayAsync(cancellationToken);

        return new CatalogList<CategoryCatalogItem>(items);
    }

    private static IQueryable<T> ApplyKeyword<T>(IQueryable<T> query, string? keyword)
        where T : class
    {
        if (string.IsNullOrWhiteSpace(keyword))
        {
            return query;
        }

        var trimmed = keyword.Trim();
        return query.Where(entity => EF.Property<string>(entity, nameof(Region.Name)).Contains(trimmed));
    }

    private static int ResolveLimit(int? limit)
    {
        return Math.Clamp(limit ?? DefaultLimit, 1, MaxLimit);
    }

    private static bool TryParseSubjectType(string? value, out SubjectType type)
    {
        return Enum.TryParse(NormalizeEnumValue(value), ignoreCase: true, out type);
    }

    private static bool TryParseModuleNodeType(string? value, out ModuleNodeType type)
    {
        return Enum.TryParse(NormalizeEnumValue(value), ignoreCase: true, out type);
    }

    private static bool TryParseCategoryType(string? value, out CategoryType type)
    {
        return Enum.TryParse(NormalizeEnumValue(value), ignoreCase: true, out type);
    }

    private static string? NormalizeEnumValue(string? value)
    {
        return string.IsNullOrWhiteSpace(value)
            ? null
            : value.Replace("_", string.Empty, StringComparison.Ordinal)
                .Replace("-", string.Empty, StringComparison.Ordinal);
    }
}