using System.Text.RegularExpressions;
using Humanizer;
using MycroForge.CLI.Commands;
using MycroForge.Core;

namespace MycroForge.CLI.CodeGen;

public class RequestClassGenerator
{
    private static readonly List<string> PythonTypingImports = ["Any", "Dict", "List", "Optional"];

    private record Import(string Name, List<string> Types)
    {
        public bool Match(string type) => Types.Any(t => type == t || type.StartsWith(t));

        public string FindType(string type) => Types.First(t => type == t || type.StartsWith(t));
    };

    private record Field(string Name, string Type);

    public enum Type
    {
        Create,
        Update
    }

    private static readonly string[] Template =
    [
        "from pydantic import BaseModel",
        "%imports%",
        "",
        "class %request_type%%entity_class_name%Request(BaseModel):",
        "%fields%",
    ];

    private static readonly Regex ImportInfoRegex = new(@"from\s+(.+)\s+import\s+(.+)");
    private static readonly Regex FieldInfoRegex = new(@"([_a-zA-Z-0-9]+)\s*:\s*Mapped\s*\[\s*(.+)\s*\]\s*=\s*.+");

    private readonly ProjectContext _context;

    public RequestClassGenerator(ProjectContext context)
    {
        _context = context;
    }

    public async Task Generate(FullyQualifiedName fqn, Type type)
    {
        var entityFilePath = Path.Join(Features.Db.FeatureName, "entities", $"{fqn.FilePath}.py");
        var entitySource = await _context.ReadFile(entityFilePath);
        var fieldInfo = ReadFields(entitySource);
        var fields = string.Join('\n', fieldInfo.Select(x => ToFieldString(x, type)));

        var requestFilePath = Path.Join(
            Features.Api.FeatureName,
            "requests",
            fqn.Namespace,
            $"{type.ToString().ToLower()}_{fqn.SnakeCasedName}_request.py"
        );

        var service = string.Join("\n", Template)
                .Replace("%imports%", GetImportString(entitySource, fieldInfo, type))
                .Replace("%request_type%", type.ToString().Pascalize())
                .Replace("%entity_class_name%", fqn.PascalizedName)
                .Replace("%fields%", fields)
            ;

        await _context.CreateFile(requestFilePath, service);
    }

    private string ToFieldString(Field field, Type type)
    {
        var @string = $"\t{field.Name}: ";

        if (type == Type.Create)
        {
            @string += $"{field.Type} = None";
        }
        else if (type == Type.Update)
        {
            @string += $"Optional[{field.Type}] = None";
        }
        else throw new Exception($"Request type {type} is not supported.");

        return @string;
    }

    private string GetImportString(string entitySource, List<Field> fields, Type type)
    {
        var imports = GetImports(entitySource);
        var importStringBuffer = type == Type.Create
            ? new Dictionary<string, List<string>>()
            : new Dictionary<string, List<string>> { ["typing"] = ["Optional"] };

        foreach (var field in fields)
        {
            /*
                The following snippet will allow importing nested types if necessary.

                var str = "List[Dict[str, Any]]";
                str = str.Replace("[", ",")
                    .Replace("]", "")
                    .Replace(" ", "");
                Console.WriteLine(str); // = "List,Dict,str,Any"
             */
            var dissectedTypes = field.Type
                .Replace("[", ",")
                .Replace("]", "")
                .Replace(" ", "")
                .Split(',');

            foreach (var dissectedType in dissectedTypes)
            {
                if (imports.FirstOrDefault(i => i.Match(dissectedType)) is Import import)
                {
                    if (!importStringBuffer.ContainsKey(import.Name))
                    {
                        importStringBuffer.Add(import.Name, []);
                    }

                    importStringBuffer[import.Name].Add(import.FindType(field.Type));
                }
            }
        }

        return string.Join("\n", importStringBuffer.Select(
            pair => $"from {pair.Key} import {string.Join(", ", pair.Value)}\n")
        );
    }

    private List<Field> ReadFields(string entitySource)
    {
        var fields = new List<Field>();
        var matches = FieldInfoRegex.Matches(entitySource);

        foreach (Match match in matches)
        {
            // Index 0 contains the full Regex match
            var fullMatch = match.Groups[0].Value;

            // Ignore primary_key fields
            if (fullMatch.IndexOf("=", StringComparison.Ordinal) <
                fullMatch.IndexOf("primary_key", StringComparison.Ordinal)) continue;

            // Ignore relationship fields, these need to be done manually
            if (fullMatch.IndexOf("=", StringComparison.Ordinal) <
                fullMatch.IndexOf("relationship(", StringComparison.Ordinal)) continue;

            var name = Clean(match.Groups[1].Value);
            var type = Clean(match.Groups[2].Value);
            fields.Add(new Field(name, type));
        }

        return fields;
    }

    private List<Import> GetImports(string entitySource)
    {
        var imports = new List<Import>();

        var matches = ImportInfoRegex.Matches(entitySource);

        foreach (Match match in matches)
        {
            // Index 0 contains the whole Regex match, so we ignore this, since we're only interested in the captured groups.
            var name = Clean(match.Groups[1].Value);
            var types = Clean(match.Groups[2].Value)
                .Split(',')
                .Select(s => s.Trim())
                .ToArray();
            imports.Add(new Import(name, new List<string>(types)));
        }

        if (imports.FirstOrDefault(i => i.Name == "typing") is Import typingImport)
        {
            typingImport.Types.AddRange(PythonTypingImports);
        }
        else
        {
            imports.Add(new Import("typing", PythonTypingImports));
        }

        return imports;
    }

    private static string Clean(string value) => value.Replace(" ", string.Empty).Trim();
}