var AllHelp = func(h map[string]HelpMessageBody) string {

    cmds := make(map[string][]string)
    for c, details := range h {
        if details.Category == "" {
            continue
        }
        cmds[details.Category] = append(cmds[details.Category], c)
    }

    // Ensure the result is deterministic.
    var categories []string
    for c, l := range cmds {
        categories = append(categories, c)
        sort.Strings(l)
    }
    sort.Strings(categories)

    // Compile the final help index.
    var buf bytes.Buffer
    w := tabwriter.NewWriter(&buf, 0, 0, 1, ' ', 0)
    for _, cat := range categories {
        fmt.Fprintf(w, "%s:\n", strings.Title(cat))
        for _, item := range cmds[cat] {
            fmt.Fprintf(w, "\t\t%s\t%s\n", item, h[item].ShortDescription)
        }
        fmt.Fprintln(w)
    }
    _ = w.Flush()
    return buf.String()
}(helpMessages)

var HelpMessages = func(h map[string]HelpMessageBody) map[string]HelpMessageBody {
    appendSeeAlso := func(newItem, prevItems string) string {

        if prevItems != "" {
            return newItem + "\n  " + prevItems
        }
        return newItem
    }
    reformatSeeAlso := func(seeAlso string) string {
        return strings.Replace(
            strings.Replace(seeAlso, ", ", "\n  ", -1),
            "WEBDOCS", base.DocsURLBase, -1)
    }
    srcMsg := h["<SOURCE>"]
    srcMsg.SeeAlso = reformatSeeAlso(strings.TrimSpace(srcMsg.SeeAlso))
    selectMsg := h["<SELECTCLAUSE>"]
    selectMsg.SeeAlso = reformatSeeAlso(strings.TrimSpace(selectMsg.SeeAlso))
    for k, m := range h {
        m = h[k]
        m.ShortDescription = strings.TrimSpace(m.ShortDescription)
        m.Text = strings.TrimSpace(m.Text)
        m.SeeAlso = strings.TrimSpace(m.SeeAlso)

        if strings.Contains(m.Text, "<source>") && k != "<SOURCE>" {
            m.Text = strings.TrimSpace(m.Text) + "\n\n" + strings.TrimSpace(srcMsg.Text)
            m.SeeAlso = appendSeeAlso(srcMsg.SeeAlso, m.SeeAlso)
        }

        if strings.Contains(m.Text, "<selectclause>") && k != "<SELECTCLAUSE>" {
            m.Text = strings.TrimSpace(m.Text) + "\n\n" + strings.TrimSpace(selectMsg.Text)
            m.SeeAlso = appendSeeAlso(selectMsg.SeeAlso, m.SeeAlso)
        }

        if strings.Contains(m.Text, "<tablename>") {
            m.SeeAlso = appendSeeAlso("SHOW TABLES", m.SeeAlso)
        }
        m.SeeAlso = reformatSeeAlso(m.SeeAlso)
        h[k] = m
    }
    return h
}(helpMessages)

type HelpMessage struct {
    // Command is set if the message is about a statement.
    Command string
    // Function is set if the message is about a built-in function.
    Function string

    // HelpMessageBody contains the details of the message.
    HelpMessageBody
}

type HelpMessageBody struct {
    Category         string
    ShortDescription string
    Text             string
    SeeAlso          string
}

type Parser struct {
    // contains filtered or unexported fields
}

type Statement struct {
    // AST is the root of the AST tree for the parsed statement.
    AST tree.Statement

    // SQL is the original SQL from which the statement was parsed. Note that this
    // is not appropriate for use in logging, as it may contain passwords and
    // other sensitive data.
    SQL string

    // NumPlaceholders indicates the number of arguments to the statement (which
    // are referenced through placeholders). This corresponds to the highest
    // argument position (i.e. the x in "$x") that appears in the query.
    //
    // Note: where there are "gaps" in the placeholder positions, this number is
    // based on the highest position encountered. For example, for `SELECT $3`,
    // NumPlaceholders is 3. These cases are malformed and will result in a
    // type-check error.
    NumPlaceholders int
}

type Statements []Statement