using ControlPlane.Core.Models;
using LibGit2Sharp;

namespace ControlPlane.Api.Endpoints;

public static class GitEndpoints
{
    public static IEndpointRouteBuilder MapGitEndpoints(this IEndpointRouteBuilder app)
    {
        app.MapGet("/api/git/log",             GetLog);
        app.MapGet("/api/git/commits/{hash}",  GetCommit);
        app.MapGet("/api/git/branches",        GetBranches);
        app.MapGet("/api/git/branch-coverage", GetBranchCoverage);
        return app;
    }

    // GET /api/git/log?grep=OPC+%23+0001&limit=50&repo=all
    // repo can be "all" (default) or a named key from Git:Repos (e.g. "Clarity", "OPC", "Gateway").
    // All responses include a repoKey field so the caller knows which repo each commit came from.
    // GET /api/git/log?grep=...&limit=25&page=1&repo=all
    // page is 1-based. Each repo contributes up to limit*page commits before merge-sort+skip/take.
    // branch filters to commits reachable from the named local branch; requires a specific repo (not "all").
    // Each result includes a branches[] array listing local branches that contain that commit.
    private static IResult GetLog(
        IConfiguration config,
        string? grep   = null,
        int     limit  = 25,
        int     page   = 1,
        string  repo   = "all",
        string? branch = null)
    {
        if (!string.IsNullOrWhiteSpace(branch) && repo == "all")
            return Results.BadRequest("'branch' filter requires a specific 'repo' parameter.");

        var repos = repo == "all"
            ? ResolveAllRepos(config)
            : ResolveNamedRepo(config, repo) is { } p
                ? new Dictionary<string, string> { [repo] = p }
                : null;

        if (repos is null || repos.Count == 0)
            return Results.Problem("Could not locate any git repositories. Set Git:Repos in appsettings.");

        var bucket = new List<(DateTimeOffset When, string RepoKey, GitCommit Commit)>();

        foreach (var (repoKey, repoPath) in repos)
        {
            if (!Directory.Exists(repoPath)) continue;

            using var r = new Repository(repoPath);

            CommitFilter filter;
            if (!string.IsNullOrWhiteSpace(branch))
            {
                var branchRef = r.Branches[branch];
                if (branchRef?.Tip is null)
                    return Results.BadRequest($"Branch '{branch}' not found in repo '{repoKey}'.");
                filter = new CommitFilter
                {
                    SortBy               = CommitSortStrategies.Topological | CommitSortStrategies.Time,
                    IncludeReachableFrom = branchRef.Tip,
                };
            }
            else
            {
                var tips = r.Branches
                    .Where(b => b.Tip != null)
                    .Select(b => (GitObject)b.Tip)
                    .ToList();
                filter = new CommitFilter
                {
                    SortBy               = CommitSortStrategies.Topological | CommitSortStrategies.Time,
                    IncludeReachableFrom = tips.Count > 0 ? tips : (object)r.Head,
                };
            }

            IEnumerable<Commit> query = r.Commits.QueryBy(filter);

            if (!string.IsNullOrWhiteSpace(grep))
                query = query.Where(c => c.Message.Contains(grep, StringComparison.OrdinalIgnoreCase));

            foreach (var c in query.Take(limit * page))
                bucket.Add((c.Author.When, repoKey, ToGitCommit(r, c)));
        }

        var pageEntries = bucket
            .OrderByDescending(x => x.When)
            .Skip((page - 1) * limit)
            .Take(limit)
            .ToList();

        // Annotate each commit with the local branches whose tip is a descendant of that commit.
        var branchMap = new Dictionary<string, List<string>>(StringComparer.Ordinal);
        foreach (var grp in pageEntries.GroupBy(x => x.RepoKey))
        {
            if (!repos.TryGetValue(grp.Key, out var rPath) || !Directory.Exists(rPath)) continue;
            using var annotRepo = new Repository(rPath);
            var localBranches = annotRepo.Branches.Where(b => !b.IsRemote && b.Tip != null).ToList();
            foreach (var (_, _, c) in grp)
            {
                var target = annotRepo.Lookup<Commit>(c.Hash);
                if (target is null) { branchMap[c.Hash] = []; continue; }
                branchMap[c.Hash] = localBranches
                    .Where(b => annotRepo.ObjectDatabase.FindMergeBase(b.Tip, target)?.Sha == target.Sha)
                    .Select(b => b.FriendlyName)
                    .ToList();
            }
        }

        var commits = pageEntries.Select(x => new
        {
            repoKey   = x.RepoKey,
            hash      = x.Commit.Hash,
            shortHash = x.Commit.ShortHash,
            author    = x.Commit.Author,
            date      = x.Commit.Date,
            subject   = x.Commit.Subject,
            files     = x.Commit.Files,
            branches  = branchMap.TryGetValue(x.Commit.Hash, out var br) ? (IReadOnlyList<string>)br : Array.Empty<string>(),
        }).ToList();

        return Results.Ok(commits);
    }

    // GET /api/git/commits/{hash}
    // Searches all registered repos — hash may belong to any of the three repos.
    private static IResult GetCommit(string hash, IConfiguration config)
    {
        var repos = ResolveAllRepos(config);
        if (repos.Count == 0)
            return Results.Problem("Could not locate any git repositories.");

        foreach (var (_, repoPath) in repos)
        {
            if (!Directory.Exists(repoPath)) continue;
            using var repo = new Repository(repoPath);
            var commit = repo.Lookup<Commit>(hash);
            if (commit is null) continue;

            var parentTree = commit.Parents.FirstOrDefault()?.Tree;
            var changes    = repo.Diff.Compare<TreeChanges>(parentTree, commit.Tree);
            var patch      = repo.Diff.Compare<Patch>(parentTree, commit.Tree);

            var files = changes.Select(c => new
            {
                path      = c.Path,
                oldPath   = c.OldPath,
                status    = c.Status.ToString(),
                additions = patch[c.Path]?.LinesAdded   ?? 0,
                deletions = patch[c.Path]?.LinesDeleted ?? 0,
                patch     = patch[c.Path]?.Patch        ?? string.Empty,
            }).ToList();

            return Results.Ok(new
            {
                hash      = commit.Sha,
                shortHash = commit.Sha[..7],
                author    = commit.Author.Name,
                email     = commit.Author.Email,
                date      = commit.Author.When.ToString("yyyy-MM-dd HH:mm:ss zzz"),
                subject   = commit.MessageShort,
                body      = commit.Message,
                files,
            });
        }

        return Results.NotFound();
    }

    // GET /api/git/branches?repo=all
    // repo defaults to "default" (single configured repo). Pass "all" to get branches from all
    // registered repos. Each result includes repoKey so the caller can group branches by repo.
    private static IResult GetBranches(IConfiguration config, string repo = "default")
    {
        if (repo == "all")
        {
            var allRepos = ResolveAllRepos(config);
            if (allRepos.Count == 0)
                return Results.Problem("Could not locate any git repositories.");

            var allBranches = new List<object>();
            foreach (var (repoKey, rPath) in allRepos)
            {
                if (!Directory.Exists(rPath)) continue;
                using var gitRepo = new Repository(rPath);
                allBranches.AddRange(gitRepo.Branches
                    .Where(b => !b.IsRemote && b.Tip != null)
                    .OrderBy(b => b.FriendlyName)
                    .Select(b => (object)new
                    {
                        repoKey,
                        name      = b.FriendlyName,
                        hash      = b.Tip.Sha,
                        shortHash = b.Tip.Sha[..7],
                        subject   = b.Tip.MessageShort,
                        author    = b.Tip.Author.Name,
                        date      = b.Tip.Author.When.ToString("yyyy-MM-dd HH:mm:ss zzz"),
                        isHead    = b.IsCurrentRepositoryHead,
                    }));
            }
            return Results.Ok(allBranches);
        }

        var repoPath = repo == "default"
            ? ResolveRepo(config)
            : ResolveNamedRepo(config, repo) ?? ResolveRepo(config);

        if (repoPath is null)
            return Results.Problem("Could not locate a git repository.");

        var repoLabel = repo == "default" ? "default" : repo;
        using var singleRepo = new Repository(repoPath);
        var branches = singleRepo.Branches
            .Where(b => !b.IsRemote && b.Tip != null)
            .OrderBy(b => b.FriendlyName)
            .Select(b => new
            {
                repoKey   = repoLabel,
                name      = b.FriendlyName,
                hash      = b.Tip.Sha,
                shortHash = b.Tip.Sha[..7],
                subject   = b.Tip.MessageShort,
                author    = b.Tip.Author.Name,
                date      = b.Tip.Author.When.ToString("yyyy-MM-dd HH:mm:ss zzz"),
                isHead    = b.IsCurrentRepositoryHead,
            })
            .ToList();

        return Results.Ok(branches);
    }

    // GET /api/git/branch-coverage?commits=hash1,hash2,hash3&repo=OPC
    // repo defaults to the single configured repo. Pass a named key from Git:Repos to
    // query a specific repo — the backend silently ignores hashes it cannot find.
    private static IResult GetBranchCoverage(IConfiguration config, string? commits = null, string? repo = null)
    {
        if (string.IsNullOrWhiteSpace(commits)) return Results.Ok(Array.Empty<object>());

        var hashes = commits.Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
        if (hashes.Length == 0) return Results.Ok(Array.Empty<object>());

        var repoPath = repo is not null
            ? ResolveNamedRepo(config, repo) ?? ResolveRepo(config)
            : ResolveRepo(config);
        if (repoPath is null)
            return Results.Problem("Could not locate a git repository.");

        using var r = new Repository(repoPath);

        var targetCommits = hashes
            .Select(h => r.Lookup<Commit>(h))
            .Where(c => c is not null)
            .ToList();

        if (targetCommits.Count == 0) return Results.Ok(Array.Empty<object>());

        var result = r.Branches
            .Where(b => !b.IsRemote && b.Tip != null)
            .Select(b =>
            {
                var contains = targetCommits.All(tc =>
                {
                    // If merge base of branch tip and target == target, then target is an ancestor
                    var mergeBase = r.ObjectDatabase.FindMergeBase(b.Tip, tc!);
                    return mergeBase?.Sha == tc!.Sha;
                });
                return new
                {
                    branch   = b.FriendlyName,
                    contains,
                    tipHash  = b.Tip.Sha[..7],
                    isHead   = b.IsCurrentRepositoryHead,
                };
            })
            .OrderBy(b => b.branch)
            .ToList();

        return Results.Ok(result);
    }

    // ── Helpers ───────────────────────────────────────────────────────────────

    /// Resolves a named repo from the Git:Repos registry.
    private static string? ResolveNamedRepo(IConfiguration config, string repoKey)
    {
        var path = config[$"Git:Repos:{repoKey}"];
        return !string.IsNullOrWhiteSpace(path) && Directory.Exists(path) ? path : null;
    }

    /// Returns all repos from the Git:Repos registry that exist on disk.
    /// Falls back to the single configured repo if the registry is empty.
    private static IReadOnlyDictionary<string, string> ResolveAllRepos(IConfiguration config)
    {
        var result = new Dictionary<string, string>();
        foreach (var child in config.GetSection("Git:Repos").GetChildren())
        {
            var path = child.Value;
            if (!string.IsNullOrWhiteSpace(path) && Directory.Exists(path))
                result[child.Key] = path;
        }
        if (result.Count == 0 && ResolveRepo(config) is { } single)
            result["default"] = single;
        return result;
    }

    /// Resolves the repo root: explicit config overrides, otherwise auto-discover
    /// from the running assembly directory upward via LibGit2Sharp.
    private static string? ResolveRepo(IConfiguration config)
    {
        var configured = config["Git:RepoRoot"] ?? config["Docker:RepoRoot"];
        if (!string.IsNullOrWhiteSpace(configured) && Directory.Exists(configured))
            return configured;

        // Auto-discover: walk up from the app's own directory
        var startPath = AppContext.BaseDirectory;
        var discovered = Repository.Discover(startPath);
        if (discovered is null) return null;

        // Repository.Discover returns the .git directory path; get the working dir
        using var probe = new Repository(discovered);
        return probe.Info.WorkingDirectory;
    }

    private static GitCommit ToGitCommit(Repository repo, Commit c)
    {
        string[] files;
        try
        {
            var parentTree = c.Parents.FirstOrDefault()?.Tree;
            var changes    = repo.Diff.Compare<TreeChanges>(parentTree, c.Tree);
            files = changes.Select(ch => ch.Path).ToArray();
        }
        catch { files = []; }

        return new GitCommit(
            Hash:      c.Sha,
            ShortHash: c.Sha[..7],
            Author:    c.Author.Name,
            Date:      c.Author.When.ToString("yyyy-MM-dd HH:mm:ss zzz"),
            Subject:   c.MessageShort,
            Files:     files
        );
    }
}