1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
const std = @import("std");
const jv = @import("../jv.zig");
const Token = @import("./tokenize.zig").Token;
const TokenKind = @import("./tokenize.zig").TokenKind;
pub const ParseError = error{
UnexpectedEnd,
InvalidQuery,
};
pub const AstKind = enum {
identity,
array_index,
object_key,
literal,
};
pub const Ast = union(AstKind) {
identity,
array_index: *Ast,
object_key: []const u8,
literal: *jv.Value,
pub fn kind(self: @This()) AstKind {
return self;
}
};
pub const TokenStream = struct {
const Self = @This();
tokens: []const Token,
current_position: usize,
pub fn init(tokens: []const Token) Self {
return .{
.tokens = tokens,
.current_position = 0,
};
}
pub fn next(self: *Self) ParseError!Token {
if (self.current_position >= self.tokens.len) {
return error.UnexpectedEnd;
}
const token = self.tokens[self.current_position];
self.current_position += 1;
return token;
}
pub fn peek(self: *Self) ParseError!Token {
if (self.current_position >= self.tokens.len) {
return error.UnexpectedEnd;
}
return self.tokens[self.current_position];
}
pub fn expect(self: *Self, expected: TokenKind) ParseError!Token {
const token = try self.next();
if (token.kind() != expected) {
return error.InvalidQuery;
}
return token;
}
};
pub fn parse(allocator: std.mem.Allocator, tokens: []const Token) !*Ast {
var token_stream = TokenStream.init(tokens);
return parseQuery(allocator, &token_stream);
}
// GRAMMAR
// query := filter
fn parseQuery(allocator: std.mem.Allocator, tokens: *TokenStream) !*Ast {
const result = try parseFilter(allocator, tokens);
_ = try tokens.expect(.end);
return result;
}
// GRAMMAR
// filter := "." accessor?
fn parseFilter(allocator: std.mem.Allocator, tokens: *TokenStream) !*Ast {
_ = try tokens.expect(.dot);
const next_token = try tokens.peek();
if (next_token.kind() == .end) {
const ast = try allocator.create(Ast);
ast.* = .identity;
return ast;
}
return parseAccessor(allocator, tokens);
}
// GRAMMAR
// accessor := field_access | index_access
fn parseAccessor(allocator: std.mem.Allocator, tokens: *TokenStream) !*Ast {
const token = try tokens.peek();
if (token.kind() == .identifier) {
return parseFieldAccess(allocator, tokens);
}
if (token.kind() == .bracket_left) {
return parseIndexAccess(allocator, tokens);
}
return error.InvalidQuery;
}
// GRAMMAR
// field_access := IDENTIFIER
fn parseFieldAccess(allocator: std.mem.Allocator, tokens: *TokenStream) !*Ast {
const token = try tokens.expect(.identifier);
const ast = try allocator.create(Ast);
ast.* = .{ .object_key = token.identifier };
return ast;
}
// GRAMMAR
// index_access := "[" NUMBER "]"
fn parseIndexAccess(allocator: std.mem.Allocator, tokens: *TokenStream) !*Ast {
_ = try tokens.expect(.bracket_left);
const index_token = try tokens.expect(.number);
_ = try tokens.expect(.bracket_right);
const index_value = try allocator.create(jv.Value);
index_value.* = .{ .integer = index_token.number };
const index_node = try allocator.create(Ast);
index_node.* = .{ .literal = index_value };
const ast = try allocator.create(Ast);
ast.* = .{ .array_index = index_node };
return ast;
}
|
