Implement broader search functionality

1 files changed, 162 insertions, 0 deletions

diff --git a/plugins/base/search.go b/plugins/base/search.go
new file mode 100644
index 0000000..4d8cef8
--- /dev/null
+++ b/plugins/base/search.go
@@ -0,0 +1,162 @@
+package alpsbase
+
+import (
+	"bufio"
+	"bytes"
+	"net/textproto"
+	"strings"
+
+	"github.com/emersion/go-imap"
+)
+
+func searchCriteriaHeader(k, v string) *imap.SearchCriteria {
+	return &imap.SearchCriteria{
+		Header: map[string][]string{
+			k: []string{v},
+		},
+	}
+}
+
+func searchCriteriaOr(criteria ...*imap.SearchCriteria) *imap.SearchCriteria {
+	if criteria[0] == nil {
+		criteria = criteria[1:]
+	}
+	or := criteria[0]
+	for _, c := range criteria[1:] {
+		or = &imap.SearchCriteria{
+			Or: [][2]*imap.SearchCriteria{{or, c}},
+		}
+	}
+	return or
+}
+
+func searchCriteriaAnd(criteria ...*imap.SearchCriteria) *imap.SearchCriteria {
+	if criteria[0] == nil {
+		criteria = criteria[1:]
+	}
+	and := criteria[0]
+	for _, c := range criteria[1:] {
+		// TODO: Maybe pitch the AND and OR functions to go-imap upstream
+		if c.Header != nil {
+			if and.Header == nil {
+				and.Header = make(textproto.MIMEHeader)
+			}
+
+			for key, value := range c.Header {
+				if _, ok := and.Header[key]; !ok {
+					and.Header[key] = nil
+				}
+				and.Header[key] = append(and.Header[key], value...)
+			}
+		}
+		and.Body = append(and.Body, c.Body...)
+		and.Text = append(and.Text, c.Text...)
+		and.WithFlags = append(and.WithFlags, c.WithFlags...)
+		and.WithoutFlags = append(and.WithoutFlags, c.WithoutFlags...)
+		// TODO: Merge more things
+	}
+	return and
+}
+
+// Splits search up into the longest string of non-functional parts and
+// functional parts
+//
+// Input: hello world foo:bar baz trains:"are cool"
+// Output: ["hello world", "foo:bar", "baz", "trains:are cool"]
+func splitSearchTokens(buf []byte, eof bool) (int, []byte, error) {
+	if len(buf) == 0 {
+		return 0, nil, nil
+	}
+
+	if buf[0] == ' ' {
+		return 1, nil, nil
+	}
+
+	colon := bytes.IndexByte(buf, byte(':'))
+	if colon == -1 && eof {
+		return len(buf), buf, nil
+	} else if colon == -1 {
+		return 0, nil, nil
+	} else {
+		space := bytes.LastIndexByte(buf[:colon], byte(' '))
+		if space != -1 {
+			return space, buf[:space], nil
+		}
+
+		var (
+			terminator int
+			quoted     bool
+		)
+		if colon + 1 < len(buf) && buf[colon+1] == byte('"') {
+			terminator = bytes.IndexByte(buf[colon+2:], byte('"'))
+			terminator += colon + 3
+			quoted = true
+		} else {
+			terminator = bytes.IndexByte(buf[colon:], byte(' '))
+			terminator += colon
+		}
+
+		if terminator == -1 {
+			return 0, nil, nil
+		} else if terminator == -1 && eof {
+			terminator = len(buf)
+		}
+
+		if quoted {
+			trimmed := append(buf[:colon+1], buf[colon+2:terminator-1]...)
+			return terminator, trimmed, nil
+		}
+
+		return terminator, buf[:terminator], nil
+	}
+}
+
+// TODO: Document search functionality somewhere
+func PrepareSearch(terms string) *imap.SearchCriteria {
+	// XXX: If Migadu's IMAP servers can learn a better Full-Text Search then
+	// we can probably start matching on the message bodies by default (gated
+	// behind some kind of flag, perhaps)
+	var criteria *imap.SearchCriteria
+
+	scanner := bufio.NewScanner(strings.NewReader(terms))
+	scanner.Split(splitSearchTokens)
+
+	for scanner.Scan() {
+		term := scanner.Text()
+		if !strings.ContainsRune(term, ':') {
+			criteria = searchCriteriaAnd(
+				criteria,
+				searchCriteriaOr(
+					searchCriteriaHeader("From", term),
+					searchCriteriaHeader("To", term),
+					searchCriteriaHeader("Cc", term),
+					searchCriteriaHeader("Subject", term),
+				),
+			)
+		} else {
+			parts := strings.SplitN(term, ":", 2)
+			key, value := parts[0], parts[1]
+			switch strings.ToLower(key) {
+			case "from":
+				criteria = searchCriteriaAnd(
+					criteria, searchCriteriaHeader("From", value))
+			case "to":
+				criteria = searchCriteriaAnd(
+					criteria, searchCriteriaHeader("To", value))
+			case "cc":
+				criteria = searchCriteriaAnd(
+					criteria, searchCriteriaHeader("Cc", value))
+			case "subject":
+				criteria = searchCriteriaAnd(
+					criteria, searchCriteriaHeader("Subject", value))
+			case "body":
+				criteria = searchCriteriaAnd(
+					criteria, &imap.SearchCriteria{Body: []string{value}})
+			default:
+				continue
+			}
+		}
+	}
+
+	return criteria
+}