Merge pull request #579 from jefftime/master
Text format to return edited ranges instead of entire document
This commit is contained in:
Lee Cannon
GitHub
commit
163409f48f
@ -18,6 +18,7 @@ const Ast = std.zig.Ast;
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const tracy = @import("tracy.zig");
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const uri_utils = @import("uri.zig");
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const data = @import("data/data.zig");
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const diff = @import("diff.zig");
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// Server fields
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@ -2228,6 +2229,9 @@ fn formattingHandler(server: *Server, writer: anytype, id: types.RequestId, req:
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.Exited => |code| if (code == 0) {
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if (std.mem.eql(u8, handle.document.text, stdout_bytes)) return try respondGeneric(writer, id, null_result_response);
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var edits = diff.edits(server.allocator, handle.document.text, stdout_bytes) catch {
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// If there was an error trying to diff the text, return the formatted response
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// as the new text for the entire range of the document
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return try send(writer, server.arena.allocator(), types.Response{
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.id = id,
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.result = .{
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@ -2239,6 +2243,32 @@ fn formattingHandler(server: *Server, writer: anytype, id: types.RequestId, req:
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},
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},
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});
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};
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defer {
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for (edits.items) |item| item.newText.deinit();
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edits.deinit();
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}
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// Convert from `[]diff.Edit` to `[]types.TextEdit`
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var text_edits = try std
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.ArrayList(types.TextEdit)
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.initCapacity(server.allocator, edits.items.len);
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defer text_edits.deinit();
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for (edits.items) |edit| {
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try text_edits.append(.{
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.range = edit.range,
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.newText = edit.newText.items,
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});
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}
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return try send(
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writer,
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server.arena.allocator(),
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types.Response{
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.id = id,
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.result = .{ .TextEdits = text_edits.items },
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},
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);
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},
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else => {},
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}
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350
src/diff.zig
Normal file
350
src/diff.zig
Normal file
@ -0,0 +1,350 @@
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const std = @import("std");
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const types = @import("types.zig");
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// This is essentially the same as `types.TextEdit`, but we use an
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// ArrayList(u8) here to be able to clean up the memory later on
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pub const Edit = struct {
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range: types.Range,
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newText: std.ArrayList(u8),
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};
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// Whether the `Change` is an addition, deletion, or no change from the
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// original string to the new string
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const Operation = enum { Deletion, Addition, Nothing };
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/// A single character difference between two strings
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const Change = struct {
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operation: Operation,
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pos: usize,
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value: ?u8,
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};
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/// Given two input strings, `a` and `b`, return a list of Edits that
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/// describe the changes from `a` to `b`
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pub fn edits(
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allocator: std.mem.Allocator,
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a: []const u8,
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b: []const u8,
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) !std.ArrayList(Edit) {
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// Given the input strings A and B, we skip over the first N characters
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// where A[0..N] == B[0..N]. We want to trim the start (and end) of the
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// strings that have the same text. This decreases the size of the LCS
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// table and makes the diff comparison more efficient
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var a_trim: []const u8 = a;
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var b_trim: []const u8 = b;
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const a_trim_offset = trim_input(&a_trim, &b_trim);
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_ = a_trim_offset;
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const rows = a_trim.len + 1;
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const cols = b_trim.len + 1;
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var lcs = try Array2D.new(allocator, rows, cols);
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defer lcs.deinit();
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calculate_lcs(&lcs, a_trim, b_trim);
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return try get_changes(
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&lcs,
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a,
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a_trim_offset,
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a_trim,
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b_trim,
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allocator,
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);
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}
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fn trim_input(a_out: *[]const u8, b_out: *[]const u8) usize {
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if (a_out.len == 0 or b_out.len == 0) return 0;
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var a: []const u8 = a_out.*;
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var b: []const u8 = b_out.*;
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// Trim the beginning of the string
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var start: usize = 0;
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while (start < a.len and start < b.len and a[start] == b[start]) : ({
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start += 1;
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}) {}
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// Trim the end of the string
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var end: usize = 1;
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while (end < a.len and end < b.len and a[a.len - end] == b[b.len - end]) : ({
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end += 1;
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}) {}
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end -= 1;
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var a_start = start;
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var a_end = a.len - end;
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var b_start = start;
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var b_end = b.len - end;
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// In certain situations, the trimmed range can be "negative" where
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// `a_start` ends up being after `a_end` in the byte stream. If you
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// consider the following inputs:
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// a: "xx gg xx"
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// b: "xx gg xx"
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//
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// This will lead to the following calculations:
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// a_start: 4
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// a_end: 4
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// b_start: 4
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// b_end: 2
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//
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// In negative range situations, we add the absolute value of the
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// the negative range's length (`b_start - b_end` in this case) to the
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// other range's length (a_end + (b_start - b_end)), and then set the
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// negative range end to the negative range start (b_end = b_start)
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if (a_start > a_end) {
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const difference = a_start - a_end;
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a_end = a_start;
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b_end += difference;
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}
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if (b_start > b_end) {
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const difference = b_start - b_end;
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b_end = b_start;
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a_end += difference;
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}
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a_out.* = a[a_start..a_end];
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b_out.* = b[b_start..b_end];
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return start;
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}
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/// A 2D array that is addressable as a[row, col]
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pub const Array2D = struct {
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const Self = @This();
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data: [*]usize,
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allocator: std.mem.Allocator,
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rows: usize,
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cols: usize,
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pub fn new(
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allocator: std.mem.Allocator,
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rows: usize,
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cols: usize,
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) !Self {
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const data = try allocator.alloc(usize, rows * cols);
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return Self{
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.data = data.ptr,
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.allocator = allocator,
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.rows = rows,
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.cols = cols,
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};
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}
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pub fn deinit(self: *Self) void {
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self.allocator.free(self.data[0 .. self.rows * self.cols]);
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}
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pub fn get(self: *Self, row: usize, col: usize) *usize {
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return @ptrCast(*usize, self.data + (row * self.cols) + col);
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}
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};
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/// Build a Longest Common Subsequence table
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fn calculate_lcs(
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lcs: *Array2D,
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astr: []const u8,
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bstr: []const u8,
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) void {
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const rows = astr.len + 1;
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const cols = bstr.len + 1;
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std.mem.set(usize, lcs.data[0 .. rows * cols], 0);
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// This approach is a dynamic programming technique to calculate the
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// longest common subsequence between two strings, `a` and `b`. We start
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// at 1 for `i` and `j` because the first column and first row are always
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// set to zero
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//
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// You can find more information about this at the following url:
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// https://en.wikipedia.org/wiki/Longest_common_subsequence_problem
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var i: usize = 1;
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while (i < rows) : (i += 1) {
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var j: usize = 1;
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while (j < cols) : (j += 1) {
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if (astr[i - 1] == bstr[j - 1]) {
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lcs.get(i, j).* = lcs.get(i - 1, j - 1).* + 1;
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} else {
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lcs.get(i, j).* = std.math.max(
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lcs.get(i - 1, j).*,
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lcs.get(i, j - 1).*,
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);
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}
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}
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}
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}
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pub fn get_changes(
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lcs: *Array2D,
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a: []const u8,
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a_trim_offset: usize,
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a_trim: []const u8,
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b_trim: []const u8,
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allocator: std.mem.Allocator,
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) !std.ArrayList(Edit) {
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// First we get a list of changes between strings at the character level:
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// "addition", "deletion", and "no change" for each character
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var changes = try std.ArrayList(Change).initCapacity(allocator, a_trim.len);
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defer changes.deinit();
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try recur_changes(
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lcs,
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&changes,
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a_trim,
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b_trim,
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@intCast(i64, a_trim.len),
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@intCast(i64, b_trim.len),
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);
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// We want to group runs of deletions and additions, and separate them by
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// runs of `.Nothing` changes. This will allow us to calculate the
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// `TextEdit` ranges
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var groups = std.ArrayList([]Change).init(allocator);
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defer groups.deinit();
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var active_change: ?[]Change = null;
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for (changes.items) |ch, i| {
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switch (ch.operation) {
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.Addition, .Deletion => {
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if (active_change == null) {
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active_change = changes.items[i..];
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}
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},
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.Nothing => {
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if (active_change) |*ac| {
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ac.* = ac.*[0..(i - (changes.items.len - ac.*.len))];
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try groups.append(ac.*);
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active_change = null;
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}
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},
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}
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}
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if (active_change) |*ac| {
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ac.* = ac.*[0..(changes.items.len - (changes.items.len - ac.*.len))];
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try groups.append(ac.*);
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}
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// The LCS algorithm works "in reverse", so we're putting everything back
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// in ascending order
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var a_lines = std.mem.split(u8, a, "\n");
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std.mem.reverse([]Change, groups.items);
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for (groups.items) |group| std.mem.reverse(Change, group);
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var edit_results = std.ArrayList(Edit).init(allocator);
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errdefer edit_results.deinit();
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// Convert our grouped changes into `Edit`s
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for (groups.items) |group| {
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var range_start = group[0].pos;
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var range_len: usize = 0;
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var newText = std.ArrayList(u8).init(allocator);
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_ = range_start;
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_ = range_len;
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for (group) |ch| {
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switch (ch.operation) {
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.Addition => try newText.append(ch.value.?),
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.Deletion => range_len += 1,
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else => {},
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}
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}
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var range = try char_pos_to_range(
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&a_lines,
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a_trim_offset + range_start,
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a_trim_offset + range_start + range_len,
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);
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a_lines.reset();
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try edit_results.append(Edit{
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.range = range,
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.newText = newText,
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});
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}
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return edit_results;
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}
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fn recur_changes(
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lcs: *Array2D,
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changes: *std.ArrayList(Change),
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a: []const u8,
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b: []const u8,
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i: i64,
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j: i64,
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) anyerror!void {
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// This function recursively works backwards through the LCS table in
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// order to figure out what kind of changes took place to transform `a`
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// into `b`
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const ii = @intCast(usize, i);
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const jj = @intCast(usize, j);
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if (i > 0 and j > 0 and a[ii - 1] == b[jj - 1]) {
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try changes.append(.{
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.operation = .Nothing,
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.pos = ii - 1,
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.value = null,
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});
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try recur_changes(lcs, changes, a, b, i - 1, j - 1);
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} else if (j > 0 and (i == 0 or lcs.get(ii, jj - 1).* >= lcs.get(ii - 1, jj).*)) {
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try changes.append(.{
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.operation = .Addition,
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.pos = ii,
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.value = b[jj - 1],
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});
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try recur_changes(lcs, changes, a, b, i, j - 1);
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} else if (i > 0 and (j == 0 or lcs.get(ii, jj - 1).* < lcs.get(ii - 1, jj).*)) {
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try changes.append(.{
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.operation = .Deletion,
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.pos = ii - 1,
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.value = a[ii - 1],
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});
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try recur_changes(lcs, changes, a, b, i - 1, j);
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}
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}
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/// Accept a range that is solely based on buffer/character position and
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/// convert it to line number & character position range
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fn char_pos_to_range(
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lines: *std.mem.SplitIterator(u8),
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start: usize,
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end: usize,
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) !types.Range {
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var char_pos: usize = 0;
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var line_pos: usize = 0;
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var result_start_pos: ?types.Position = null;
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var result_end_pos: ?types.Position = null;
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while (lines.next()) |line| : ({
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char_pos += line.len + 1;
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line_pos += 1;
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}) {
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if (start >= char_pos and start <= char_pos + line.len) {
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result_start_pos = .{
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.line = @intCast(i64, line_pos),
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.character = @intCast(i64, start - char_pos),
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};
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}
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if (end >= char_pos and end <= char_pos + line.len) {
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result_end_pos = .{
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.line = @intCast(i64, line_pos),
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.character = @intCast(i64, end - char_pos),
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};
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}
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}
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if (result_start_pos == null) return error.InvalidRange;
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// If we did not find an end position, it is outside the range of the
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// string for some reason so clamp it to the string end position
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if (result_end_pos == null) {
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result_end_pos = types.Position{
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.line = @intCast(i64, line_pos),
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.character = @intCast(i64, char_pos),
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};
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}
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return types.Range{
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.start = result_start_pos.?,
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.end = result_end_pos.?,
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};
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}
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