using StellaOps.Signals.Scm.Models;
using System.Globalization;
using System.Text.Json;

namespace StellaOps.Signals.Scm.Webhooks;

/// <summary>
/// Maps GitHub webhook events to normalized SCM events.
/// </summary>
public sealed class GitHubEventMapper : IScmEventMapper
{
    public ScmProvider Provider => ScmProvider.GitHub;

    public NormalizedScmEvent? Map(string eventType, string deliveryId, JsonElement payload)
    {
        var (scmEventType, extractor) = eventType.ToLowerInvariant() switch
        {
            "push" => (ScmEventType.Push, (Func<JsonElement, (ScmEventType, string?, string?)>)ExtractPushDetails),
            "pull_request" => (ScmEventType.Unknown, ExtractPullRequestDetails),
            "release" => (ScmEventType.ReleasePublished, ExtractReleaseDetails),
            "create" => (ScmEventType.Unknown, ExtractCreateDetails),
            "workflow_run" => (ScmEventType.Unknown, ExtractWorkflowRunDetails),
            "check_run" => (ScmEventType.Unknown, ExtractCheckRunDetails),
            _ => (ScmEventType.Unknown, (Func<JsonElement, (ScmEventType, string?, string?)>?)null)
        };

        // Unsupported event types return null
        if (extractor is null)
        {
            return null;
        }

        var repository = ExtractRepository(payload);
        if (repository is null && scmEventType != ScmEventType.Unknown)
        {
            return null;
        }

        repository ??= new ScmRepository
        {
            FullName = "unknown"
        };

        var (extractedType, commitSha, refName) = extractor(payload);
        if (extractedType != ScmEventType.Unknown)
        {
            scmEventType = extractedType;
        }

        return new NormalizedScmEvent
        {
            EventId = deliveryId,
            Provider = ScmProvider.GitHub,
            EventType = scmEventType,
            Timestamp = ExtractTimestamp(payload),
            Repository = repository,
            Actor = ExtractActor(payload),
            Ref = refName ?? GetString(payload, "ref"),
            CommitSha = commitSha ?? GetNestedString(payload, "head_commit", "id"),
            PullRequest = ExtractPullRequest(payload),
            Release = ExtractRelease(payload),
            Pipeline = ExtractWorkflow(payload)
        };
    }

    private static (ScmEventType, string?, string?) ExtractPushDetails(JsonElement payload)
    {
        var sha = GetNestedString(payload, "head_commit", "id") ?? GetString(payload, "after");
        var refName = GetString(payload, "ref");
        return (ScmEventType.Push, sha, refName);
    }

    private static (ScmEventType, string?, string?) ExtractPullRequestDetails(JsonElement payload)
    {
        var action = GetString(payload, "action");
        var eventType = action switch
        {
            "opened" or "reopened" => ScmEventType.PullRequestOpened,
            "closed" when GetNestedBool(payload, "pull_request", "merged") => ScmEventType.PullRequestMerged,
            "closed" => ScmEventType.PullRequestClosed,
            _ => ScmEventType.Unknown
        };

        var sha = GetNestedString(payload, "pull_request", "head", "sha");
        var refName = GetNestedString(payload, "pull_request", "head", "ref");
        return (eventType, sha, refName);
    }

    private static (ScmEventType, string?, string?) ExtractReleaseDetails(JsonElement payload)
    {
        var action = GetString(payload, "action");
        if (action != "published")
        {
            return (ScmEventType.Unknown, null, null);
        }

        var tagName = GetNestedString(payload, "release", "tag_name");
        return (ScmEventType.ReleasePublished, null, tagName);
    }

    private static (ScmEventType, string?, string?) ExtractCreateDetails(JsonElement payload)
    {
        var refType = GetString(payload, "ref_type");
        if (refType != "tag")
        {
            return (ScmEventType.Unknown, null, null);
        }

        var refName = GetString(payload, "ref");
        return (ScmEventType.TagCreated, null, refName);
    }

    private static (ScmEventType, string?, string?) ExtractWorkflowRunDetails(JsonElement payload)
    {
        var action = GetString(payload, "action");
        var conclusion = GetNestedString(payload, "workflow_run", "conclusion");

        var eventType = action switch
        {
            "requested" or "in_progress" => ScmEventType.PipelineStarted,
            "completed" when conclusion == "success" => ScmEventType.PipelineSucceeded,
            "completed" => ScmEventType.PipelineFailed,
            _ => ScmEventType.Unknown
        };

        var sha = GetNestedString(payload, "workflow_run", "head_sha");
        var refName = GetNestedString(payload, "workflow_run", "head_branch");
        return (eventType, sha, refName);
    }

    private static (ScmEventType, string?, string?) ExtractCheckRunDetails(JsonElement payload)
    {
        var action = GetString(payload, "action");
        var status = GetNestedString(payload, "check_run", "status");
        var conclusion = GetNestedString(payload, "check_run", "conclusion");

        var eventType = (action, status, conclusion) switch
        {
            ("created", _, _) => ScmEventType.PipelineStarted,
            ("completed", _, "success") => ScmEventType.PipelineSucceeded,
            ("completed", _, _) => ScmEventType.PipelineFailed,
            _ => ScmEventType.Unknown
        };

        var sha = GetNestedString(payload, "check_run", "head_sha");
        return (eventType, sha, null);
    }

    private static ScmRepository? ExtractRepository(JsonElement payload)
    {
        if (!payload.TryGetProperty("repository", out var repo))
        {
            return null;
        }

        return new ScmRepository
        {
            Id = GetString(repo, "id")?.ToString(),
            FullName = GetString(repo, "full_name") ?? string.Empty,
            Owner = GetNestedString(repo, "owner", "login"),
            Name = GetString(repo, "name"),
            CloneUrl = GetString(repo, "clone_url"),
            DefaultBranch = GetString(repo, "default_branch"),
            IsPrivate = GetBool(repo, "private")
        };
    }

    private static ScmActor? ExtractActor(JsonElement payload)
    {
        if (!payload.TryGetProperty("sender", out var sender))
        {
            return null;
        }

        var actorType = GetString(sender, "type") switch
        {
            "User" => ScmActorType.User,
            "Bot" => ScmActorType.Bot,
            _ => ScmActorType.Unknown
        };

        return new ScmActor
        {
            Id = GetString(sender, "id")?.ToString(),
            Username = GetString(sender, "login"),
            Type = actorType
        };
    }

    private static ScmPullRequest? ExtractPullRequest(JsonElement payload)
    {
        if (!payload.TryGetProperty("pull_request", out var pr))
        {
            return null;
        }

        var state = GetString(pr, "state") ?? GetString(payload, "action");

        return new ScmPullRequest
        {
            Number = GetInt(pr, "number"),
            Title = GetString(pr, "title"),
            SourceBranch = GetNestedString(pr, "head", "ref"),
            TargetBranch = GetNestedString(pr, "base", "ref"),
            State = state,
            Url = GetString(pr, "html_url")
        };
    }

    private static ScmRelease? ExtractRelease(JsonElement payload)
    {
        if (!payload.TryGetProperty("release", out var release))
        {
            return null;
        }

        return new ScmRelease
        {
            Id = GetString(release, "id")?.ToString(),
            TagName = GetString(release, "tag_name"),
            Name = GetString(release, "name"),
            IsPrerelease = GetBool(release, "prerelease"),
            IsDraft = GetBool(release, "draft"),
            Url = GetString(release, "html_url")
        };
    }

    private static ScmPipeline? ExtractWorkflow(JsonElement payload)
    {
        if (!payload.TryGetProperty("workflow_run", out var run))
        {
            if (!payload.TryGetProperty("check_run", out var checkRun))
            {
                return null;
            }

            return new ScmPipeline
            {
                Id = GetString(checkRun, "id")?.ToString(),
                Name = GetString(checkRun, "name"),
                Status = GetString(checkRun, "status") switch
                {
                    "queued" => ScmPipelineStatus.Queued,
                    "in_progress" => ScmPipelineStatus.InProgress,
                    "completed" => ScmPipelineStatus.Completed,
                    _ => ScmPipelineStatus.Unknown
                },
                Conclusion = GetString(checkRun, "conclusion"),
                Url = GetString(checkRun, "html_url")
            };
        }

        return new ScmPipeline
        {
            Id = GetString(run, "id")?.ToString(),
            Name = GetString(run, "name"),
            RunNumber = GetLong(run, "run_number"),
            Status = GetString(run, "status") switch
            {
                "queued" => ScmPipelineStatus.Queued,
                "in_progress" => ScmPipelineStatus.InProgress,
                "completed" => ScmPipelineStatus.Completed,
                _ => ScmPipelineStatus.Unknown
            },
            Conclusion = GetString(run, "conclusion"),
            Url = GetString(run, "html_url")
        };
    }

    private static DateTimeOffset ExtractTimestamp(JsonElement payload)
    {
        var timestamp = GetNestedString(payload, "head_commit", "timestamp")
            ?? GetNestedString(payload, "workflow_run", "updated_at")
            ?? GetNestedString(payload, "workflow_run", "created_at")
            ?? GetNestedString(payload, "pull_request", "updated_at")
            ?? GetNestedString(payload, "pull_request", "created_at")
            ?? GetNestedString(payload, "release", "published_at")
            ?? GetNestedString(payload, "check_run", "completed_at")
            ?? GetNestedString(payload, "check_run", "started_at");

        return TryParseTimestamp(timestamp) ?? DateTimeOffset.UnixEpoch;
    }

    private static DateTimeOffset? TryParseTimestamp(string? value)
    {
        if (string.IsNullOrWhiteSpace(value))
        {
            return null;
        }

        return DateTimeOffset.TryParse(
            value,
            CultureInfo.InvariantCulture,
            DateTimeStyles.AssumeUniversal | DateTimeStyles.AdjustToUniversal,
            out var parsed)
            ? parsed
            : null;
    }

    private static string? GetString(JsonElement element, string property)
    {
        return element.TryGetProperty(property, out var value) && value.ValueKind == JsonValueKind.String
            ? value.GetString()
            : null;
    }

    private static bool GetBool(JsonElement element, string property)
    {
        return element.TryGetProperty(property, out var value) &&
               value.ValueKind == JsonValueKind.True;
    }

    private static int GetInt(JsonElement element, string property)
    {
        return element.TryGetProperty(property, out var value) && value.ValueKind == JsonValueKind.Number
            ? value.GetInt32()
            : 0;
    }

    private static long GetLong(JsonElement element, string property)
    {
        return element.TryGetProperty(property, out var value) && value.ValueKind == JsonValueKind.Number
            ? value.GetInt64()
            : 0;
    }

    private static string? GetNestedString(JsonElement element, params string[] path)
    {
        var current = element;
        foreach (var prop in path)
        {
            if (!current.TryGetProperty(prop, out current))
            {
                return null;
            }
        }

        return current.ValueKind == JsonValueKind.String ? current.GetString() : null;
    }

    private static bool GetNestedBool(JsonElement element, params string[] path)
    {
        var current = element;
        foreach (var prop in path)
        {
            if (!current.TryGetProperty(prop, out current))
            {
                return false;
            }
        }

        return current.ValueKind == JsonValueKind.True;
    }
}