package httpapi

import (
	"context"
	"io"
	"net/http"

	"git.yeij.top/AskaEth/Scoreboard/server/internal/auth"
	"git.yeij.top/AskaEth/Scoreboard/server/internal/rules"
)

// rulesRoutes 挂载规则包的导出与导入（导入支持 ?preview=1 只预览差异）。
func (s *server) rulesRoutes(mux *http.ServeMux) {
	mux.HandleFunc("GET /api/rules/export", s.read(auth.RoleAdmin, s.exportRules))
	mux.HandleFunc("POST /api/rules/import", s.write(auth.RoleAdmin, s.importRules))
}

func (s *server) exportRules(w http.ResponseWriter, r *http.Request) (any, error) {
	pack, err := rules.Export(s.ev, rules.Meta{})
	if err != nil {
		return nil, internal(err)
	}
	body, err := rules.Marshal(pack)
	if err != nil {
		return nil, internal(err)
	}
	w.Header().Set("Content-Type", "application/yaml; charset=utf-8")
	w.Header().Set("Content-Disposition", `attachment; filename="rules.yaml"`)
	if _, err := w.Write(body); err != nil {
		s.logger.Error("规则包写出失败", "err", err)
	}
	return nil, errHandled
}

func (s *server) importRules(w http.ResponseWriter, r *http.Request) (any, error) {
	body, err := io.ReadAll(io.LimitReader(r.Body, 4<<20))
	if err != nil {
		return nil, badRequest("读取请求体失败", nil)
	}
	if len(body) == 0 {
		return nil, badRequest("请求体为空", nil)
	}

	pack, err := rules.Parse(body)
	if err != nil {
		return nil, badRequest(err.Error(), nil)
	}
	cur, err := rules.Load(s.ev)
	if err != nil {
		return nil, internal(err)
	}
	cs, err := rules.Diff(cur, pack)
	if err != nil {
		return nil, badRequest(err.Error(), nil)
	}

	// 先预览再落地：?preview=1 只返回差异。
	if r.URL.Query().Get("preview") == "1" {
		return cs, nil
	}

	res, err := rules.Apply(s.ev, cs)
	if err != nil {
		return nil, internal(err)
	}
	// 分值一变，历史成绩的积分必须全量重算。
	if err := s.recomputeAllEvents(r.Context(), middlewareUserID(r)); err != nil {
		return nil, internal(err)
	}
	s.audit(r.Context(), "rules.import", "rules", 0, nil, res)
	return res, nil
}

// recomputeAllEvents 逐项目重算积分流水，用于规则包导入等会改变分值的场景。
func (s *server) recomputeAllEvents(ctx context.Context, actorID int64) error {
	rows, err := s.ev.QueryContext(ctx, `SELECT id FROM events`)
	if err != nil {
		return err
	}
	var ids []int64
	for rows.Next() {
		var id int64
		if err := rows.Scan(&id); err != nil {
			_ = rows.Close()
			return err
		}
		ids = append(ids, id)
	}
	if err := rows.Close(); err != nil {
		return err
	}
	if err := rows.Err(); err != nil {
		return err
	}

	for _, eventID := range ids {
		tx, err := s.ev.BeginTx(ctx, nil)
		if err != nil {
			return err
		}
		if _, err := recomputeLedgerTx(ctx, tx, eventID, 0, actorID, "rules-import"); err != nil {
			_ = tx.Rollback()
			return err
		}
		// 重算改动了积分，必须写版本号并推送，否则大屏停在旧比分。
		if err := s.bumpStandings(ctx, tx, actorID); err != nil {
			_ = tx.Rollback()
			return err
		}
		if err := tx.Commit(); err != nil {
			return err
		}
	}
	return nil
}