using System.Data.Common;
using Microsoft.EntityFrameworkCore;

namespace MeterVault.Integration.Tests;

[Collection("Timescale")]
public sealed class SchemaTests(TimescaleFixture fx)
{
    [Fact]
    public async Task Migrations_are_applied()
    {
        await using var ctx = fx.CreateContext();
        var applied = (await ctx.Database.GetAppliedMigrationsAsync()).ToList();

        Assert.Contains(applied, m => m.EndsWith("InitialSchema", StringComparison.Ordinal));
        Assert.Contains(applied, m => m.EndsWith("TimescaleHypertables", StringComparison.Ordinal));
        Assert.Contains(applied, m => m.EndsWith("AnalysisRollups", StringComparison.Ordinal));
    }

    [Fact]
    public async Task The_continuous_aggregates_and_their_refresh_jobs_are_gone()
    {
        // D-17: nothing read them, they were Berlin-only and stale; the analysis tables replace them.
        await using var ctx = fx.CreateContext();
        var conn = ctx.Database.GetDbConnection();
        await conn.OpenAsync();

        Assert.Empty(await QueryStringsAsync(conn,
            "SELECT view_name::text FROM timescaledb_information.continuous_aggregates;"));
        Assert.Empty(await QueryStringsAsync(conn,
            "SELECT proc_name::text FROM timescaledb_information.jobs WHERE proc_name = 'policy_refresh_continuous_aggregate';"));
        Assert.Empty(await QueryStringsAsync(conn,
            "SELECT relname::text FROM pg_class WHERE relname IN ('consumption_daily', 'consumption_monthly', 'consumption_yearly');"));
    }

    [Fact]
    public async Task The_analysis_tables_are_plain_tables_that_go_with_their_meter()
    {
        // D-12: plain tables (the hypertable list above stays reading + consumption), each tied to its meter by a
        // cascading foreign key, so deleting a meter — or wiping all of them — never trips over them.
        await using var ctx = fx.CreateContext();
        var conn = ctx.Database.GetDbConnection();
        await conn.OpenAsync();

        var cascading = await QueryStringsAsync(conn,
            "SELECT tc.table_name::text FROM information_schema.table_constraints tc " +
            "JOIN information_schema.referential_constraints rc ON rc.constraint_name = tc.constraint_name " +
            "JOIN information_schema.constraint_column_usage cu ON cu.constraint_name = tc.constraint_name " +
            "WHERE tc.constraint_type = 'FOREIGN KEY' AND rc.delete_rule = 'CASCADE' AND cu.table_name = 'meter' " +
            "AND tc.table_name IN ('consumption_rollup', 'consumption_rollup_month', 'meter_coverage', 'meter_rollup_state') " +
            "ORDER BY 1;");

        Assert.Equal(["consumption_rollup", "consumption_rollup_month", "meter_coverage", "meter_rollup_state"], cascading);
    }

    [Fact]
    public async Task Reading_and_consumption_are_hypertables()
    {
        await using var ctx = fx.CreateContext();
        var conn = ctx.Database.GetDbConnection();
        await conn.OpenAsync();

        var names = await QueryStringsAsync(conn,
            "SELECT hypertable_name FROM timescaledb_information.hypertables ORDER BY hypertable_name;");

        Assert.Equal(["consumption", "reading"], names);
    }

    [Fact]
    public async Task Reading_has_a_compression_policy()
    {
        await using var ctx = fx.CreateContext();
        var conn = ctx.Database.GetDbConnection();
        await conn.OpenAsync();

        // A compression/columnstore policy shows up as a scheduled job against the hypertable.
        var jobs = await QueryStringsAsync(conn,
            "SELECT hypertable_name FROM timescaledb_information.jobs " +
            "WHERE proc_name IN ('policy_compression', 'policy_columnstore') AND hypertable_name = 'reading';");

        Assert.Contains("reading", jobs);
    }

    private static async Task<List<string>> QueryStringsAsync(DbConnection conn, string sql)
    {
        await using var cmd = conn.CreateCommand();
        cmd.CommandText = sql;
        var results = new List<string>();
        await using var reader = await cmd.ExecuteReaderAsync();
        while (await reader.ReadAsync())
        {
            results.Add(reader.GetString(0));
        }

        return results;
    }
}