Bind history to the recipient session and channel, not the name (closes #148)

History was selected by msg_to, so whoever next held a released nick, or
created a deleted channel again under its old name, could read the
earlier holder's messages. Each message row now records the session a
DM or INVITE was sent to (to_session_id) and the channel a channel
message was sent to (to_channel_id), and GET /api/v1/history selects by
the one that applies, using its index. A session's DM history now also
follows it across nick changes. A DM or channel message whose recipient
is deleted before it is stored gets the unknown nick or channel error.

Model: opus-5-5

internal/db/queries.go

@@ -9,6 +9,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"math"
 	"strconv"
 	"strings"
 	"time"
@@ -940,9 +941,14 @@ func (database *Database) GetSessionChannelIDs(
 }
 
 // InsertMessage stores a message and returns its DB ID.
+// toSessionID is the session a DM or INVITE is sent to and
+// toChannelID the channel a channel message is sent to;
+// GetHistory selects by them. Pass 0 for one that does not
+// apply, which stores NULL.
 func (database *Database) InsertMessage(
 	ctx context.Context,
 	command, from, target string,
+	toSessionID, toChannelID int64,
 	params json.RawMessage,
 	body json.RawMessage,
 	meta json.RawMessage,
@@ -965,9 +971,12 @@ func (database *Database) InsertMessage(
 	res, err := database.conn.ExecContext(ctx,
 		`INSERT INTO messages
 		 (uuid, command, msg_from, msg_to,
+		  to_session_id, to_channel_id,
 		  params, body, meta, created_at)
-		 VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
+		 VALUES (?, ?, ?, ?, NULLIF(?, 0), NULLIF(?, 0),
+		  ?, ?, ?, ?)`,
 		msgUUID, command, from, target,
+		toSessionID, toChannelID,
 		string(params), string(body), string(meta), now)
 	if err != nil {
 		return 0, "", fmt.Errorf(
@@ -1058,26 +1067,31 @@ func (database *Database) PollMessages(
 	return msgs, lastQID, nil
 }
 
-// GetHistory returns message history for a target. A
-// non-empty before is the id of a message sent to target,
-// and only messages older than it are returned; an id with
-// no such message gives an error wrapping sql.ErrNoRows.
+// GetHistory returns the PRIVMSG history of one recipient:
+// the DMs sent to session toSessionID, or the messages sent
+// to channel toChannelID. Pass 0 for the other. A non-empty
+// before is the id of a PRIVMSG in that history, and only
+// messages older than it are returned; an id with no such
+// message gives an error wrapping sql.ErrNoRows.
 func (database *Database) GetHistory(
 	ctx context.Context,
-	target, before string,
+	toSessionID, toChannelID int64,
+	before string,
 	limit int,
 ) ([]IRCMessage, error) {
 	if limit <= 0 {
 		limit = defaultHistLimit
 	}
 
-	var beforeID int64
+	// With no before, every message is older than this.
+	beforeID := int64(math.MaxInt64)
 
 	if before != "" {
 		err := database.conn.QueryRowContext(ctx,
 			`SELECT id FROM messages
-			 WHERE uuid = ? AND msg_to = ?`,
-			before, target,
+			 WHERE uuid = ? AND command = 'PRIVMSG'
+			   AND (to_session_id = ? OR to_channel_id = ?)`,
+			before, toSessionID, toChannelID,
 		).Scan(&beforeID)
 		if err != nil {
 			return nil, fmt.Errorf(
@@ -1087,7 +1101,7 @@ func (database *Database) GetHistory(
 	}
 
 	rows, err := database.queryHistory(
-		ctx, target, beforeID, limit,
+		ctx, toSessionID, toChannelID, beforeID, limit,
 	)
 	if err != nil {
 		return nil, err
@@ -1107,21 +1121,23 @@ func (database *Database) GetHistory(
 	return msgs, nil
 }
 
+// queryHistory selects by to_session_id when toSessionID is
+// set and by to_channel_id otherwise, so that the column's
+// (column, id) index serves the order and the limit.
 func (database *Database) queryHistory(
 	ctx context.Context,
-	target string,
-	beforeID int64,
+	toSessionID, toChannelID, beforeID int64,
 	limit int,
 ) (*sql.Rows, error) {
-	if beforeID > 0 {
+	if toSessionID != 0 {
 		rows, err := database.conn.QueryContext(ctx,
 			`SELECT id, uuid, command, msg_from,
 			   msg_to, params, body, meta, created_at
 			 FROM messages
-			 WHERE msg_to = ? AND id < ?
+			 WHERE to_session_id = ? AND id < ?
 			   AND command = 'PRIVMSG'
 			 ORDER BY id DESC LIMIT ?`,
-			target, beforeID, limit)
+			toSessionID, beforeID, limit)
 		if err != nil {
 			return nil, fmt.Errorf(
 				"query history: %w", err,
@@ -1135,10 +1151,10 @@ func (database *Database) queryHistory(
 		`SELECT id, uuid, command, msg_from,
 		   msg_to, params, body, meta, created_at
 		 FROM messages
-		 WHERE msg_to = ?
+		 WHERE to_channel_id = ? AND id < ?
 		   AND command = 'PRIVMSG'
 		 ORDER BY id DESC LIMIT ?`,
-		target, limit)
+		toChannelID, beforeID, limit)
 	if err != nil {
 		return nil, fmt.Errorf("query history: %w", err)
 	}