1 files changed, 49 insertions, 3 deletions

diff --git a/src/pardes.zig b/src/pardes.zig
index eb9aa11f..f0d22d57 100644
--- a/src/pardes.zig
+++ b/src/pardes.zig
@@ -1112,6 +1112,36 @@ test "first document fallback splits like Tty from the originating pane" {
     };
 }
 
+test "Lspwhy after a Hover asks to explain that hover, at its place" {
+    if (!lsp.supports.contains(.hover)) return error.SkipZigTest;
+    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
+    defer p.deinit();
+    const pane = try p.setTestFile("const a = 1;\nconst b = a;\n");
+    const f = &pane.file.?;
+    p.gpa.free(f.path);
+    f.path = try p.gpa.dupe(u8, "/tmp/x.zig");
+    while (p.nextEffect()) |_| {}
+    pane.body.cur_row = 1;
+    pane.body.cur_col = 10;
+    p.lspRequest(0, .hover, "");
+    var hover_at: u32 = 0;
+    while (p.nextEffect()) |e| if (e == .lsp) {
+        hover_at = e.lsp.offset;
+    };
+    pane.body.cur_row = 0;
+    pane.body.cur_col = 0;
+    p.lsp_wait = null;
+    p.lspRequest(0, .explain, "");
+    var seen = false;
+    while (p.nextEffect()) |e| if (e == .lsp) {
+        try std.testing.expectEqual(lsp.Kind.explain, e.lsp.kind);
+        try std.testing.expectEqualStrings("hover ", e.lsp.arg.slice());
+        try std.testing.expectEqual(hover_at, e.lsp.offset);
+        seen = true;
+    };
+    try std.testing.expect(seen);
+}
+
 test "the Tutor pane is named +Tutor in the session's directory, never a bare path at the root" {
     const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true });
     defer p.deinit();
@@ -3553,7 +3583,9 @@ pub const Effect = union(enum) {
     write_dump,
     set_clipboard,
     read_clipboard,
-    lsp: struct { id: u32, kind: lsp.Kind, pane: u8, offset: u32, arg: Buf(128) },
+    /// `arg` up to 128 bytes, or for `explain` the query it explains,
+    /// `<kind> <arg>`.
+    lsp: struct { id: u32, kind: lsp.Kind, pane: u8, offset: u32, arg: Buf(160) },
     /// Snapshot the matching request with pipeRequest(id), then run it away
     /// from the UI/event loop and answer with pipe_resp.
     pipe: struct { id: u32 },
@@ -4351,6 +4383,9 @@ pub const Pardes = struct {
     can_ask: bool = false,
 
     lsp_seq: u32 = 0,
+    /// The last query asked (Lspwhy explains it): its kind, argument, and
+    /// the pane and place it was asked at.
+    lsp_last: ?struct { kind: lsp.Kind, arg: Effect.Buf(128), serial: u32, offset: u32 } = null,
     lsp_wait: ?struct {
         id: u32,
         kind: lsp.Kind,
@@ -6295,6 +6330,17 @@ pub const Pardes = struct {
             .row = @intCast(@max(0, pane.body.cur_row)),
             .col = @intCast(@max(0, pane.body.cur_col)),
         }) else 0;
+        // Lspwhy asks the last query again, narrated: its kind and argument,
+        // at its place when asked from its pane. None yet: a definition.
+        var explained: [160]u8 = undefined;
+        var sent = arg;
+        var at = off;
+        if (kind == .explain) {
+            if (p.lsp_last) |last| {
+                sent = std.fmt.bufPrint(&explained, "{s} {s}", .{ @tagName(last.kind), last.arg.slice() }) catch "";
+                if (last.serial == pane.serial) at = last.offset;
+            }
+        } else if (kind != .status) p.lsp_last = .{ .kind = kind, .arg = .from(arg), .serial = pane.serial, .offset = @intCast(off) };
         p.lsp_seq +%= 1;
         // A 9P write that asked it is answered once the answer is in.
         if (p.fs.serving) p.fs.lsp_answer_at = turn.lsp_answers;
@@ -6312,8 +6358,8 @@ pub const Pardes = struct {
             .id = p.lsp_seq,
             .kind = kind,
             .pane = @intCast(id),
-            .offset = @intCast(off),
-            .arg = .from(arg),
+            .offset = @intCast(at),
+            .arg = .from(sent),
         } });
     }