// Package queryapi: handler implementations for the BotService user
// routes. M2 covers session create/get/list and scope patch. Plan §3
// mandates singular `/client/{clientId}/...` routes; the OpenAPI spec
// declares them that way and the generated ServerInterface wires the
// path params into these handlers.
//
// Every handler:
//  1. Extracts the authenticated Cognito subject via cognitoauth.GetUserSubject.
//     Returns 401 when the subject is missing.
//  2. Calls the bot.Service method with the (clientID, actor) tuple.
//  3. Maps the bot.Err* sentinels onto HTTP status codes via mapBotError.
//  4. Translates the service-layer Session into the generated
//     BotSessionResponse / BotSessionListResponse.
package queryapi

import (
	"encoding/json"
	"errors"
	"log/slog"
	"net/http"

	"queryorchestration/internal/bot"
	"queryorchestration/internal/cognitoauth"

	"github.com/google/uuid"
	"github.com/labstack/echo/v4"
	"github.com/oapi-codegen/nullable"
	openapi_types "github.com/oapi-codegen/runtime/types"
)

const (
	defaultBotListLimit  = 20
	defaultBotListOffset = 0
)

// CreateBotSession is POST /client/{clientId}/bot/sessions.
//
// Body is an empty CreateBotSessionRequest object (placeholder for
// future fields). The service mints the session id and timestamps;
// title remains empty until M4's first turn arrives.
func (s *Controllers) CreateBotSession(ctx echo.Context, clientId BotClientID) error {
	actor, ok := cognitoauth.GetUserSubject(ctx)
	if !ok {
		return echo.NewHTTPError(http.StatusUnauthorized, "missing user subject")
	}
	session, err := s.svc.Bot.CreateSession(ctx.Request().Context(), clientId, actor)
	if err != nil {
		return mapBotError(err)
	}
	resp, err := sessionToResponse(session)
	if err != nil {
		return echo.NewHTTPError(http.StatusInternalServerError, "failed to encode session response")
	}
	return ctx.JSON(http.StatusCreated, resp)
}

// GetBotSession is GET /client/{clientId}/bot/sessions/{sessionId}.
// Owner-scoped read: returns 404 when the session does not match
// (clientId, actor, is_deleted=false).
func (s *Controllers) GetBotSession(ctx echo.Context, clientId BotClientID, sessionId BotSessionID) error {
	actor, ok := cognitoauth.GetUserSubject(ctx)
	if !ok {
		return echo.NewHTTPError(http.StatusUnauthorized, "missing user subject")
	}
	session, err := s.svc.Bot.GetSessionForOwner(ctx.Request().Context(), uuid.UUID(sessionId), clientId, actor)
	if err != nil {
		return mapBotError(err)
	}
	resp, err := sessionToResponse(session)
	if err != nil {
		return echo.NewHTTPError(http.StatusInternalServerError, "failed to encode session response")
	}
	return ctx.JSON(http.StatusOK, resp)
}

// ListBotSessions is GET /client/{clientId}/bot/sessions.
//
// Owner-scoped list, paged by limit/offset. Each item carries up to
// MinTurnLimit(limit, cfg.RecentTurns) preview turns.
func (s *Controllers) ListBotSessions(ctx echo.Context, clientId BotClientID, params ListBotSessionsParams) error {
	actor, ok := cognitoauth.GetUserSubject(ctx)
	if !ok {
		return echo.NewHTTPError(http.StatusUnauthorized, "missing user subject")
	}
	limit, offset, err := resolveListBotSessionParams(params.Limit, params.Offset)
	if err != nil {
		return err
	}
	sessions, err := s.svc.Bot.ListSessionsForOwner(ctx.Request().Context(), clientId, actor, bot.ListSessionsInput{
		Limit:  limit,
		Offset: offset,
	})
	if err != nil {
		return mapBotError(err)
	}
	return ctx.JSON(http.StatusOK, sessionsToListResponse(sessions))
}

// PatchBotSessionScope is PATCH /client/{clientId}/bot/sessions/{sessionId}/scope.
func (s *Controllers) PatchBotSessionScope(ctx echo.Context, clientId BotClientID, sessionId BotSessionID) error {
	actor, ok := cognitoauth.GetUserSubject(ctx)
	if !ok {
		return echo.NewHTTPError(http.StatusUnauthorized, "missing user subject")
	}
	var req BotSessionScopePatchRequest
	if err := ctx.Bind(&req); err != nil {
		slog.Error("failed to parse scope patch request", "error", err)
		return echo.NewHTTPError(http.StatusBadRequest, "invalid request body")
	}
	input := bot.PatchScopeInput{
		AddDocuments:    derefUUIDList(req.AddDocuments),
		RemoveDocuments: derefUUIDList(req.RemoveDocuments),
		AddFolders:      derefUUIDList(req.AddFolders),
		RemoveFolders:   derefUUIDList(req.RemoveFolders),
	}
	session, err := s.svc.Bot.PatchScope(ctx.Request().Context(), uuid.UUID(sessionId), clientId, actor, input)
	if err != nil {
		return mapBotError(err)
	}
	resp, err := sessionToResponse(session)
	if err != nil {
		return echo.NewHTTPError(http.StatusInternalServerError, "failed to encode session response")
	}
	return ctx.JSON(http.StatusOK, resp)
}

// resolveListBotSessionParams normalises and validates the optional
// limit/offset query params. Plan §3 mandates limit in [1, 200] and
// offset >= 0; this is the gate before the service layer.
func resolveListBotSessionParams(limitPtr, offsetPtr *int32) (int, int, error) {
	limit := defaultBotListLimit
	offset := defaultBotListOffset
	if limitPtr != nil {
		limit = int(*limitPtr)
	}
	if offsetPtr != nil {
		offset = int(*offsetPtr)
	}
	if limit < 1 || limit > 200 {
		return 0, 0, echo.NewHTTPError(http.StatusBadRequest, "limit must be in [1, 200]")
	}
	if offset < 0 {
		return 0, 0, echo.NewHTTPError(http.StatusBadRequest, "offset must be >= 0")
	}
	return limit, offset, nil
}

// derefUUIDList unpacks the optional pointer-to-slice that oapi-codegen
// emits for nullable arrays into a plain slice. nil input returns a
// non-nil empty slice so service-layer dedup helpers see a consistent
// shape.
func derefUUIDList(in *[]openapi_types.UUID) []uuid.UUID {
	if in == nil {
		return []uuid.UUID{}
	}
	out := make([]uuid.UUID, 0, len(*in))
	for _, id := range *in {
		out = append(out, uuid.UUID(id))
	}
	return out
}

// mapBotError translates internal/bot sentinel errors into HTTP errors.
// M4 sentinels live in mapBotTurnError so the M2/M3 cases below stay
// short. Any unrecognized error is logged and surfaced as 500.
func mapBotError(err error) error {
	if turnMapped := mapBotTurnError(err); turnMapped != nil {
		return turnMapped
	}
	switch {
	case errors.Is(err, bot.ErrSessionNotFound):
		return echo.NewHTTPError(http.StatusNotFound, "session not found")
	case errors.Is(err, bot.ErrAddRemoveConflict):
		return echo.NewHTTPError(http.StatusBadRequest, "add_remove_conflict")
	case errors.Is(err, bot.ErrDocumentCrossClient):
		return echo.NewHTTPError(http.StatusBadRequest, "document_cross_client")
	case errors.Is(err, bot.ErrFolderCrossClient):
		return echo.NewHTTPError(http.StatusBadRequest, "folder_cross_client")
	case errors.Is(err, bot.ErrInvalidLimit):
		return echo.NewHTTPError(http.StatusBadRequest, err.Error())
	case errors.Is(err, bot.ErrInvalidOffset):
		return echo.NewHTTPError(http.StatusBadRequest, err.Error())
	case errors.Is(err, bot.ErrMissingClientID):
		return echo.NewHTTPError(http.StatusBadRequest, "clientId is required")
	}
	slog.Error("bot handler internal error", "error", err)
	return echo.NewHTTPError(http.StatusInternalServerError, "internal server error")
}

// sessionToResponse converts the service-layer Session into the
// generated BotSessionResponse type. State is unmarshalled into a
// map[string]interface{} so the wire shape is a JSON object, not a
// base64 string. recentTurns is omitted from single-session reads
// (where the service did not populate them).
func sessionToResponse(s *bot.Session) (BotSessionResponse, error) {
	stateMap := map[string]interface{}{}
	if len(s.State) > 0 {
		if err := json.Unmarshal(s.State, &stateMap); err != nil {
			return BotSessionResponse{}, err
		}
	}
	docs := make([]openapi_types.UUID, 0, len(s.Scope.DocumentIDs))
	for _, id := range s.Scope.DocumentIDs {
		docs = append(docs, openapi_types.UUID(id))
	}
	folders := make([]openapi_types.UUID, 0, len(s.Scope.FolderIDs))
	for _, id := range s.Scope.FolderIDs {
		folders = append(folders, openapi_types.UUID(id))
	}
	previews := previewsToResponse(s.RecentTurns)
	if previews == nil {
		previews = []BotTurnPreview{}
	}
	resp := BotSessionResponse{
		Id:        openapi_types.UUID(s.ID),
		ClientId:  s.ClientID,
		CreatedBy: s.CreatedBy,
		Title:     s.Title,
		State:     stateMap,
		LastTurn:  s.LastTurn,
		CreatedAt: s.CreatedAt,
		UpdatedAt: s.UpdatedAt,
		Scope: BotSessionScope{
			DocumentIds: docs,
			FolderIds:   folders,
		},
		RecentTurns: previews,
	}
	return resp, nil
}

// previewsToResponse converts service-layer turn previews into the
// generated BotTurnPreview slice. Returns nil for empty input so
// callers can decide whether to substitute an empty slice.
func previewsToResponse(in []bot.TurnPreview) []BotTurnPreview {
	if len(in) == 0 {
		return nil
	}
	out := make([]BotTurnPreview, 0, len(in))
	for _, p := range in {
		row := BotTurnPreview{
			Ordinal:   p.Ordinal,
			Prompt:    p.Prompt,
			Status:    BotTurnPreviewStatus(p.Status),
			CreatedAt: p.CreatedAt,
		}
		if p.Completion != nil {
			row.Completion = nullable.NewNullableWithValue(*p.Completion)
		} else {
			row.Completion = nullable.NewNullNullable[string]()
		}
		out = append(out, row)
	}
	return out
}

// sessionsToListResponse builds the wire shape for list endpoints. The
// list always emits a non-nil array even when empty.
func sessionsToListResponse(in []*bot.Session) BotSessionListResponse {
	out := BotSessionListResponse{
		Sessions: make([]BotSessionResponse, 0, len(in)),
	}
	for _, s := range in {
		resp, err := sessionToResponse(s)
		if err != nil {
			// json.Marshal of an in-memory map[string]interface{}
			// effectively cannot fail here; log and keep going.
			slog.Error("encode session in list", "error", err, "session_id", s.ID)
			continue
		}
		out.Sessions = append(out.Sessions, resp)
	}
	return out
}