1// Copyright 2009 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// This file contains the infrastructure to create a code
6// snippet for search results.
7//
8// Note: At the moment, this only creates HTML snippets.
9
10package godoc
11
12import (
13	"bytes"
14	"fmt"
15	"go/ast"
16	"go/token"
17)
18
19type Snippet struct {
20	Line int
21	Text string // HTML-escaped
22}
23
24func (p *Presentation) newSnippet(fset *token.FileSet, decl ast.Decl, id *ast.Ident) *Snippet {
25	// TODO instead of pretty-printing the node, should use the original source instead
26	var buf1 bytes.Buffer
27	p.writeNode(&buf1, nil, fset, decl)
28	// wrap text with <pre> tag
29	var buf2 bytes.Buffer
30	buf2.WriteString("<pre>")
31	FormatText(&buf2, buf1.Bytes(), -1, true, id.Name, nil)
32	buf2.WriteString("</pre>")
33	return &Snippet{fset.Position(id.Pos()).Line, buf2.String()}
34}
35
36func findSpec(list []ast.Spec, id *ast.Ident) ast.Spec {
37	for _, spec := range list {
38		switch s := spec.(type) {
39		case *ast.ImportSpec:
40			if s.Name == id {
41				return s
42			}
43		case *ast.ValueSpec:
44			for _, n := range s.Names {
45				if n == id {
46					return s
47				}
48			}
49		case *ast.TypeSpec:
50			if s.Name == id {
51				return s
52			}
53		}
54	}
55	return nil
56}
57
58func (p *Presentation) genSnippet(fset *token.FileSet, d *ast.GenDecl, id *ast.Ident) *Snippet {
59	s := findSpec(d.Specs, id)
60	if s == nil {
61		return nil //  declaration doesn't contain id - exit gracefully
62	}
63
64	// only use the spec containing the id for the snippet
65	dd := &ast.GenDecl{
66		Doc:    d.Doc,
67		TokPos: d.Pos(),
68		Tok:    d.Tok,
69		Lparen: d.Lparen,
70		Specs:  []ast.Spec{s},
71		Rparen: d.Rparen,
72	}
73
74	return p.newSnippet(fset, dd, id)
75}
76
77func (p *Presentation) funcSnippet(fset *token.FileSet, d *ast.FuncDecl, id *ast.Ident) *Snippet {
78	if d.Name != id {
79		return nil //  declaration doesn't contain id - exit gracefully
80	}
81
82	// only use the function signature for the snippet
83	dd := &ast.FuncDecl{
84		Doc:  d.Doc,
85		Recv: d.Recv,
86		Name: d.Name,
87		Type: d.Type,
88	}
89
90	return p.newSnippet(fset, dd, id)
91}
92
93// NewSnippet creates a text snippet from a declaration decl containing an
94// identifier id. Parts of the declaration not containing the identifier
95// may be removed for a more compact snippet.
96func NewSnippet(fset *token.FileSet, decl ast.Decl, id *ast.Ident) *Snippet {
97	// TODO(bradfitz, adg): remove this function.  But it's used by indexer, which
98	// doesn't have a *Presentation, and NewSnippet needs a TabWidth.
99	var p Presentation
100	p.TabWidth = 4
101	return p.NewSnippet(fset, decl, id)
102}
103
104// NewSnippet creates a text snippet from a declaration decl containing an
105// identifier id. Parts of the declaration not containing the identifier
106// may be removed for a more compact snippet.
107func (p *Presentation) NewSnippet(fset *token.FileSet, decl ast.Decl, id *ast.Ident) *Snippet {
108	var s *Snippet
109	switch d := decl.(type) {
110	case *ast.GenDecl:
111		s = p.genSnippet(fset, d, id)
112	case *ast.FuncDecl:
113		s = p.funcSnippet(fset, d, id)
114	}
115
116	// handle failure gracefully
117	if s == nil {
118		var buf bytes.Buffer
119		fmt.Fprintf(&buf, `<span class="alert">could not generate a snippet for <span class="highlight">%s</span></span>`, id.Name)
120		s = &Snippet{fset.Position(id.Pos()).Line, buf.String()}
121	}
122	return s
123}
124