Local queries (#641)

* Read local queries from pgweb home directory
* Refactor local query functionality
* Allow picking local query in the query tab
* WIP
* Disable local query dropdown during execution
* Only allow local queries running in a single session mode
* Add middleware to enforce local query endpoint availability
* Fix query check
* Add query store tests
* Make query store errors portable
* Skip building specific tests on windows

pkg/queries/metadata.go

@@ -0,0 +1,148 @@
+package queries
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var (
+	reMetaPrefix  = regexp.MustCompile(`(?m)^\s*--\s*pgweb:\s*(.+)`)
+	reMetaContent = regexp.MustCompile(`([\w]+)\s*=\s*"([^"]+)"`)
+	reMatchAll    = regexp.MustCompile(`^(.+)$`)
+	reExpression  = regexp.MustCompile(`[\[\]\(\)\+\*]+`)
+
+	allowedKeys  = []string{"title", "description", "host", "user", "database", "mode", "timeout"}
+	allowedModes = map[string]bool{"readonly": true, "*": true}
+)
+
+type Metadata struct {
+	Title       string
+	Description string
+	Host        field
+	User        field
+	Database    field
+	Mode        field
+	Timeout     *time.Duration
+}
+
+func parseMetadata(input string) (*Metadata, error) {
+	fields, err := parseFields(input)
+	if err != nil {
+		return nil, err
+	}
+	if fields == nil {
+		return nil, nil
+	}
+
+	// Host must be set to limit queries availability
+	if fields["host"] == "" {
+		return nil, fmt.Errorf("host field must be set")
+	}
+
+	// Allow matching for any user, database and mode by default
+	if fields["user"] == "" {
+		fields["user"] = "*"
+	}
+	if fields["database"] == "" {
+		fields["database"] = "*"
+	}
+	if fields["mode"] == "" {
+		fields["mode"] = "*"
+	}
+
+	hostField, err := newField(fields["host"])
+	if err != nil {
+		return nil, fmt.Errorf(`error initializing "host" field: %w`, err)
+	}
+
+	userField, err := newField(fields["user"])
+	if err != nil {
+		return nil, fmt.Errorf(`error initializing "user" field: %w`, err)
+	}
+
+	dbField, err := newField(fields["database"])
+	if err != nil {
+		return nil, fmt.Errorf(`error initializing "database" field: %w`, err)
+	}
+
+	if !allowedModes[fields["mode"]] {
+		return nil, fmt.Errorf(`invalid "mode" field value: %q`, fields["mode"])
+	}
+	modeField, err := newField(fields["mode"])
+	if err != nil {
+		return nil, fmt.Errorf(`error initializing "mode" field: %w`, err)
+	}
+
+	var timeout *time.Duration
+	if fields["timeout"] != "" {
+		timeoutSec, err := strconv.Atoi(fields["timeout"])
+		if err != nil {
+			return nil, fmt.Errorf(`error initializing "timeout" field: %w`, err)
+		}
+		timeoutVal := time.Duration(timeoutSec) * time.Second
+		timeout = &timeoutVal
+	}
+
+	return &Metadata{
+		Title:       fields["title"],
+		Description: fields["description"],
+		Host:        hostField,
+		User:        userField,
+		Database:    dbField,
+		Mode:        modeField,
+		Timeout:     timeout,
+	}, nil
+}
+
+func parseFields(input string) (map[string]string, error) {
+	result := map[string]string{}
+	seenKeys := map[string]bool{}
+
+	allowed := map[string]bool{}
+	for _, key := range allowedKeys {
+		allowed[key] = true
+	}
+
+	matches := reMetaPrefix.FindAllStringSubmatch(input, -1)
+	if len(matches) == 0 {
+		return nil, nil
+	}
+
+	for _, match := range matches {
+		content := reMetaContent.FindAllStringSubmatch(match[1], -1)
+		if len(content) == 0 {
+			continue
+		}
+
+		for _, field := range content {
+			key := field[1]
+			value := field[2]
+
+			if !allowed[key] {
+				return result, fmt.Errorf("unknown key: %q", key)
+			}
+			if seenKeys[key] {
+				return result, fmt.Errorf("duplicate key: %q", key)
+			}
+
+			seenKeys[key] = true
+			result[key] = value
+		}
+	}
+
+	return result, nil
+}
+
+func sanitizeMetadata(input string) string {
+	lines := []string{}
+	for _, line := range strings.Split(input, "\n") {
+		line = reMetaPrefix.ReplaceAllString(line, "")
+		if len(line) > 0 {
+			lines = append(lines, line)
+		}
+	}
+	return strings.Join(lines, "\n")
+}