// handleContent fetches the content of a document from the Bigtable and returns it.
func handleContent(w http.ResponseWriter, r *http.Request, table *bigtable.Table) {
ctx, _ := context.WithTimeout(context.Background(), 10*time.Second)
name := r.FormValue("name")
if len(name) == 0 {
http.Error(w, "No document name supplied.", http.StatusBadRequest)
return
}
row, err := table.ReadRow(ctx, name)
if err != nil {
http.Error(w, "Error reading content: "+err.Error(), http.StatusInternalServerError)
return
}
content := row[contentColumnFamily]
if len(content) == 0 {
http.Error(w, "Document not found.", http.StatusNotFound)
return
}
var buf bytes.Buffer
if err := contentTemplate.ExecuteTemplate(&buf, "", struct{ Title, Content string }{name, string(content[0].Value)}); err != nil {
http.Error(w, "Error executing HTML template: "+err.Error(), http.StatusInternalServerError)
return
}
io.Copy(w, &buf)
}
// handleAddDoc adds a document to the index.
func handleAddDoc(w http.ResponseWriter, r *http.Request, table *bigtable.Table) {
if r.Method != "POST" {
http.Error(w, "POST requests only", http.StatusMethodNotAllowed)
return
}
ctx, _ := context.WithTimeout(context.Background(), time.Minute)
name := r.FormValue("name")
if len(name) == 0 {
http.Error(w, "Empty document name!", http.StatusBadRequest)
return
}
content := r.FormValue("content")
if len(content) == 0 {
http.Error(w, "Empty document content!", http.StatusBadRequest)
return
}
var (
writeErr error // Set if any write fails.
mu sync.Mutex // Protects writeErr
wg sync.WaitGroup // Used to wait for all writes to finish.
)
// writeOneColumn writes one column in one row, updates err if there is an error,
// and signals wg that one operation has finished.
writeOneColumn := func(row, family, column, value string, ts bigtable.Timestamp) {
mut := bigtable.NewMutation()
mut.Set(family, column, ts, []byte(value))
err := table.Apply(ctx, row, mut)
if err != nil {
mu.Lock()
writeErr = err
mu.Unlock()
}
}
// Start a write to store the document content.
wg.Add(1)
go func() {
writeOneColumn(name, contentColumnFamily, "", content, bigtable.Now())
wg.Done()
}()
// Start writes to store the document name in the index for each word in the document.
words := tokenize(content)
for _, word := range words {
var (
row = word
family = indexColumnFamily
column = name
value = ""
ts = bigtable.Now()
)
wg.Add(1)
go func() {
// TODO: should use a semaphore to limit the number of concurrent writes.
writeOneColumn(row, family, column, value, ts)
wg.Done()
}()
}
wg.Wait()
if writeErr != nil {
http.Error(w, "Error writing to Bigtable: "+writeErr.Error(), http.StatusInternalServerError)
return
}
var buf bytes.Buffer
if err := addTemplate.ExecuteTemplate(&buf, "", struct{ Title string }{name}); err != nil {
http.Error(w, "Error executing HTML template: "+err.Error(), http.StatusInternalServerError)
return
}
io.Copy(w, &buf)
}
// handleSearch responds to search queries, returning links and snippets for matching documents.
func handleSearch(w http.ResponseWriter, r *http.Request, table *bigtable.Table) {
ctx, _ := context.WithTimeout(context.Background(), 10*time.Second)
query := r.FormValue("q")
// Split the query into words.
words := tokenize(query)
if len(words) == 0 {
http.Error(w, "Empty query.", http.StatusBadRequest)
return
}
// readRows reads from many rows concurrently.
readRows := func(rows []string) ([]bigtable.Row, error) {
results := make([]bigtable.Row, len(rows))
errors := make([]error, len(rows))
var wg sync.WaitGroup
for i, row := range rows {
wg.Add(1)
go func(i int, row string) {
defer wg.Done()
results[i], errors[i] = table.ReadRow(ctx, row, bigtable.RowFilter(bigtable.LatestNFilter(1)))
}(i, row)
}
wg.Wait()
for _, err := range errors {
if err != nil {
return nil, err
}
}
return results, nil
}
// For each query word, get the list of documents containing it.
results, err := readRows(words)
if err != nil {
http.Error(w, "Error reading index: "+err.Error(), http.StatusInternalServerError)
return
}
// Count how many of the query words each result contained.
hits := make(map[string]int)
for _, r := range results {
for _, r := range r[indexColumnFamily] {
hits[r.Column]++
}
}
// Build a slice of all the documents that matched every query word.
var matches []string
for doc, count := range hits {
if count == len(words) {
matches = append(matches, doc[len(indexColumnFamily+":"):])
}
}
// Fetch the content of those documents from the Bigtable.
content, err := readRows(matches)
if err != nil {
http.Error(w, "Error reading results: "+err.Error(), http.StatusInternalServerError)
return
}
type result struct{ Title, Snippet string }
data := struct {
Query string
Results []result
}{query, nil}
// Output links and snippets.
for i, doc := range matches {
var text string
c := content[i][contentColumnFamily]
if len(c) > 0 {
text = string(c[0].Value)
}
if len(text) > 100 {
text = text[:100] + "..."
}
data.Results = append(data.Results, result{doc, text})
}
var buf bytes.Buffer
if err := searchTemplate.ExecuteTemplate(&buf, "", data); err != nil {
http.Error(w, "Error executing HTML template: "+err.Error(), http.StatusInternalServerError)
return
}
io.Copy(w, &buf)
}