add path param lure customization

Signed-off-by: RonniSkansing <rskansing@gmail.com>

backend/database/campaign.go

@@ -64,6 +64,15 @@ type Campaign struct {
 	WebhookIncludeData string `gorm:"not null;default:'full'"`
 	WebhookEvents      int    `gorm:"not null;default:0"`
 
+	// LureURLMode, LureCodeAlgo and LureCodeLength are snapshotted from the
+	// campaign template when the campaign is scheduled. Reading them from the
+	// campaign rather than the template keeps recipients added later to a self
+	// managed campaign consistent with the ones already scheduled, and keeps a
+	// template edit from changing the form of URLs already delivered.
+	LureURLMode    string `gorm:"not null;default:'query'"`
+	LureCodeAlgo   string `gorm:"not null;default:'crockford32'"`
+	LureCodeLength int    `gorm:"not null;default:12"`
+
 	// has one
 	CampaignTemplateID *uuid.UUID `gorm:"index;type:uuid;"`
 	CampaignTemplate   *CampaignTemplate

backend/database/campaignRecipient.go

@@ -4,6 +4,7 @@ import (
 	"time"
 
 	"github.com/google/uuid"
+	"gorm.io/gorm"
 )
 
 const (
@@ -45,8 +46,70 @@ type CampaignRecipient struct {
 	// NotableEventID is the most notable event for this recipient
 	NotableEvent   *Event     `gorm:"foreignKey:NotableEventID;references:ID"`
 	NotableEventID *uuid.UUID `gorm:"type:uuid;index"`
+
+	// LureCode is the short identifier that appears in the lure URL instead of
+	// the campaign recipient UUID, for example https://example.com/4H7K9QM2XR3T.
+	// It is stored exactly as written and matched exactly, which is what lets an
+	// operator pick a code such as Special-42 and get that link verbatim.
+	//
+	// Releasing a code sets this back to null. Nulling rather than flagging is
+	// what keeps a reclaimed code from still showing against its former owner,
+	// and it lets the unique index below need nothing but IS NOT NULL.
+	LureCode *string `gorm:"type:varchar(64)"`
+	// LureCodeCustom marks a code the operator set by hand. A custom code cannot
+	// be told apart from a generated one by shape, so the distinction is stored.
+	LureCodeCustom bool `gorm:"not null;default:false"`
 }
 
 func (CampaignRecipient) TableName() string {
 	return CAMPAIGN_RECIPIENT_TABLE_NAME
 }
+
+// Migrate creates the partial unique index backing lure code allocation.
+//
+// The predicate has to exclude rows carrying no code, otherwise every recipient
+// in a query mode campaign enters the index under the same value and the second
+// insert fails. Because releasing a code nulls it, that single predicate also
+// covers reuse: a released code leaves the index and is free to claim again.
+//
+// This is raw SQL rather than a gorm index tag because only the sqlite driver
+// emits the WHERE clause. The generic migrator drops it, which would silently
+// produce a full unique index and break reuse.
+func (CampaignRecipient) Migrate(db *gorm.DB) error {
+	// lure_code is the only code column this table carries. AutoMigrate adds
+	// columns but never drops them, so any other lure column and its indexes are
+	// removed here. errors are ignored because on a fresh install there is
+	// nothing to drop.
+	db.Exec(`DROP INDEX IF EXISTS idx_campaign_recipients_lure_code_lookup`)
+	db.Exec(`DROP INDEX IF EXISTS idx_campaign_recipients_lure_code_released_at`)
+	db.Exec(`DROP INDEX IF EXISTS idx_campaign_recipients_lure_code_folded`)
+	db.Exec(`ALTER TABLE campaign_recipients DROP COLUMN lure_code_lookup`)
+	db.Exec(`ALTER TABLE campaign_recipients DROP COLUMN lure_code_released_at`)
+	db.Exec(`ALTER TABLE campaign_recipients DROP COLUMN lure_code_folded`)
+
+	createIndex := func() error {
+		return db.Exec(`CREATE UNIQUE INDEX IF NOT EXISTS idx_campaign_recipients_lure_code
+			ON campaign_recipients (lure_code)
+			WHERE lure_code IS NOT NULL`).Error
+	}
+	err := createIndex()
+	if err == nil {
+		return nil
+	}
+
+	// the index fails when two rows already hold the same code. keep the first
+	// row for each code and release the rest, then build the index.
+	//
+	// this runs only after a failure, because the scan and grouping it needs
+	// are too costly to pay on every startup.
+	if dedupErr := db.Exec(`UPDATE campaign_recipients SET lure_code = NULL
+		WHERE lure_code IS NOT NULL
+		  AND rowid NOT IN (
+		    SELECT MIN(rowid) FROM campaign_recipients
+		    WHERE lure_code IS NOT NULL
+		    GROUP BY lure_code
+		  )`).Error; dedupErr != nil {
+		return dedupErr
+	}
+	return createIndex()
+}

backend/database/campaignTemplate.go

@@ -21,6 +21,18 @@ type CampaignTemplate struct {
 
 	URLPath string `gorm:"not null;default:'';index"`
 
+	// LureURLMode selects how a delivered lure URL carries the recipient
+	// identifier. "query" appends ?id=<uuid>, "path" appends /<code> after
+	// URLPath. The resolver accepts both forms regardless of this setting, so
+	// changing it never breaks links that are already out.
+	LureURLMode string `gorm:"not null;default:'query'"`
+	// LureCodeAlgo names the generator that allocates codes for campaigns
+	// created from this template.
+	LureCodeAlgo string `gorm:"not null;default:'crockford32'"`
+	// LureCodeLength is the number of characters in a generated code. Shorter
+	// codes are easier to read aloud and easier to guess.
+	LureCodeLength int `gorm:"not null;default:12"`
+
 	// IsUsable indicates if a template is usable based on if it has all the required
 	// data such as domainID, landingPage and etc to be used in a campaign
 	IsUsable bool `gorm:"not null;default:false;index"`