package bot

import (
	"time"

	"queryorchestration/internal/database/repository"

	"github.com/google/uuid"
)

// sessionListRow is a small in-package shape that lets ListSessionsForOwner
// and ListSessionsForSuperAdmin share decorateSessionList without a generic
// or interface assertion at every site. The two underlying sqlc rows have
// the same columns but distinct Go types (per sqlc's row-per-query rule),
// so we copy the field values once at the boundary.
type sessionListRow struct {
	id           uuid.UUID
	clientID     string
	createdBy    string
	title        string
	state        []byte
	createdAt    time.Time
	updatedAt    time.Time
	lastTerminal int32
	isDeleted    bool
}

// rowsOwner adapts ListBotSessionsForOwnerRow rows to the shared shape.
func rowsOwner(rows []*repository.ListBotSessionsForOwnerRow) []sessionListRow {
	out := make([]sessionListRow, 0, len(rows))
	for _, r := range rows {
		out = append(out, sessionListRow{
			id:           r.ID,
			clientID:     r.ClientID,
			createdBy:    r.CreatedBy,
			title:        r.Title,
			state:        r.State,
			createdAt:    r.CreatedAt.Time,
			updatedAt:    r.UpdatedAt.Time,
			lastTerminal: r.LastTerminalOrdinal,
			isDeleted:    r.IsDeleted,
		})
	}
	return out
}

// rowsSuperAdmin adapts ListBotSessionsForSuperAdminRow rows to the shared
// shape. Identical to rowsOwner but on a different generated type.
func rowsSuperAdmin(rows []*repository.ListBotSessionsForSuperAdminRow) []sessionListRow {
	out := make([]sessionListRow, 0, len(rows))
	for _, r := range rows {
		out = append(out, sessionListRow{
			id:           r.ID,
			clientID:     r.ClientID,
			createdBy:    r.CreatedBy,
			title:        r.Title,
			state:        r.State,
			createdAt:    r.CreatedAt.Time,
			updatedAt:    r.UpdatedAt.Time,
			lastTerminal: r.LastTerminalOrdinal,
			isDeleted:    r.IsDeleted,
		})
	}
	return out
}

// dedupUUIDs returns the input slice with duplicates removed, preserving
// first-seen order. Returns a non-nil empty slice for nil input so the
// caller can pass the result directly to set-comparison helpers.
func dedupUUIDs(in []uuid.UUID) []uuid.UUID {
	if len(in) == 0 {
		return []uuid.UUID{}
	}
	seen := make(map[uuid.UUID]struct{}, len(in))
	out := make([]uuid.UUID, 0, len(in))
	for _, id := range in {
		if _, ok := seen[id]; ok {
			continue
		}
		seen[id] = struct{}{}
		out = append(out, id)
	}
	return out
}

// hasIntersection returns true when sets a and b share at least one
// element. Both inputs are expected to be deduplicated already.
func hasIntersection(a, b []uuid.UUID) bool {
	if len(a) == 0 || len(b) == 0 {
		return false
	}
	set := make(map[uuid.UUID]struct{}, len(a))
	for _, id := range a {
		set[id] = struct{}{}
	}
	for _, id := range b {
		if _, ok := set[id]; ok {
			return true
		}
	}
	return false
}

// computeUnion returns (existing - remove) ∪ add as a deduplicated
// slice in deterministic order: first the surviving existing ids in
// their original order, then any new add ids that are not already in
// the surviving set. The bot_session_documents / bot_session_folders
// PRIMARY KEY guarantees `existing` is already deduplicated when read
// from SQL, so the loop can rely on that invariant.
func computeUnion(existing, add, remove []uuid.UUID) []uuid.UUID {
	removeSet := make(map[uuid.UUID]struct{}, len(remove))
	for _, id := range remove {
		removeSet[id] = struct{}{}
	}
	out := make([]uuid.UUID, 0, len(existing)+len(add))
	seen := make(map[uuid.UUID]struct{}, len(existing)+len(add))
	for _, id := range existing {
		if _, dropped := removeSet[id]; dropped {
			continue
		}
		seen[id] = struct{}{}
		out = append(out, id)
	}
	for _, id := range add {
		if _, dup := seen[id]; dup {
			continue
		}
		seen[id] = struct{}{}
		out = append(out, id)
	}
	return out
}