package api

import (
	"errors"
	"log"
	"net/http"
	"strconv"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgconn"

	"booklib/internal/auth"
)

func isUnique(e error) bool {
	var pgErr *pgconn.PgError
	return errors.As(e, &pgErr) && pgErr.Code == "23505"
}

func (a *api) listUsers(c *gin.Context) {
	users, e := a.st.ListUsers(c)
	if e != nil {
		log.Printf("db: %v", e)
		err(c, http.StatusInternalServerError, "internal", "db error")
		return
	}
	out := make([]gin.H, 0, len(users))
	for _, u := range users {
		out = append(out, gin.H{"id": u.ID, "username": u.Username, "role": u.Role,
			"created_at": u.CreatedAt.Format(time.RFC3339)})
	}
	c.JSON(http.StatusOK, out)
}

func (a *api) createUser(c *gin.Context) {
	var req struct{ Username, Password, Role string }
	if c.ShouldBindJSON(&req) != nil {
		err(c, http.StatusBadRequest, "bad_request", "json body required")
		return
	}
	if req.Role != "admin" && req.Role != "member" {
		err(c, http.StatusBadRequest, "bad_request", "role must be admin|member")
		return
	}
	if len(req.Password) < 8 {
		err(c, http.StatusBadRequest, "bad_request", "password too short (min 8)")
		return
	}
	h, e := auth.HashPassword(req.Password)
	if e != nil {
		err(c, http.StatusInternalServerError, "internal", "hash")
		return
	}
	id, e := a.st.CreateUser(c, req.Username, h, req.Role)
	if e != nil {
		if isUnique(e) {
			err(c, http.StatusConflict, "exists", "username taken")
			return
		}
		err(c, http.StatusBadRequest, "bad_request", "invalid input")
		return
	}
	c.JSON(http.StatusCreated, gin.H{"id": id, "username": req.Username, "role": req.Role})
}

func (a *api) deleteUser(c *gin.Context) {
	id, e := strconv.ParseInt(c.Param("id"), 10, 64)
	if e != nil {
		err(c, http.StatusBadRequest, "bad_request", "bad id")
		return
	}
	if id == uid(c) {
		err(c, http.StatusBadRequest, "bad_request", "cannot delete yourself")
		return
	}
	target, e := a.st.GetUserByID(c, id)
	if e != nil {
		if errors.Is(e, pgx.ErrNoRows) {
			err(c, http.StatusNotFound, "not_found", "no such user")
			return
		}
		err(c, http.StatusInternalServerError, "internal", "db error")
		return
	}
	if target.Role == "admin" {
		n, _ := a.st.CountAdmins(c) // 防删光最后一个 admin
		if n <= 1 {
			err(c, http.StatusBadRequest, "bad_request", "cannot delete the last admin")
			return
		}
	}
	if e := a.st.DeleteUser(c, id); e != nil {
		err(c, http.StatusInternalServerError, "internal", "db error")
		return
	}
	c.Status(http.StatusNoContent)
}