package api

import (
	"database/sql"
	"encoding/json"
	"git.misaka.ren/m1saka/dsh-web/internal/store"
	"golang.org/x/crypto/bcrypt"
	"io"
	"net/http"
	"os"
	"regexp"
	"strconv"
	"time"
)

var usernamePattern = regexp.MustCompile("^[a-zA-Z0-9_-]{3,40}$")

func DefaultQuota() int64 {
	if n, err := strconv.ParseInt(os.Getenv("DEFAULT_QUOTA_BYTES"), 10, 64); err == nil && n > 0 {
		return n
	}
	return 10 << 30
}

func (a *API) users(w http.ResponseWriter, r *http.Request) {
	u, _, err := a.user(r)
	if err != nil {
		fail(w, 401, "authentication required")
		return
	}
	if !u.Admin {
		fail(w, 403, "administrator required")
		return
	}
	switch r.Method {
	case "GET":
		rows, err := a.s.DB.Query("SELECT id,username,admin,quota,created FROM users ORDER BY created")
		if err != nil {
			fail(w, 500, "database error")
			return
		}
		defer rows.Close()
		out := []store.User{}
		for rows.Next() {
			var v store.User
			var created int64
			if err := rows.Scan(&v.ID, &v.Username, &v.Admin, &v.Quota, &created); err != nil {
				fail(w, 500, "database error")
				return
			}
			v.Created = time.Unix(created, 0)
			out = append(out, v)
		}
		if err := rows.Err(); err != nil {
			fail(w, 500, "database error")
			return
		}
		writeJSON(w, out)
	case "POST":
		var in struct {
			Username string
			Password string
			Admin    bool
			Quota    int64 `json:"quota_bytes"`
		}
		if json.NewDecoder(r.Body).Decode(&in) != nil || !usernamePattern.MatchString(in.Username) || len(in.Password) < 12 || len(in.Password) > 72 || in.Quota < 0 {
			fail(w, 400, "username must be 3–40 letters/digits/_/-, password 12–72 bytes, quota nonnegative")
			return
		}
		if in.Quota == 0 {
			in.Quota = DefaultQuota()
		}
		h, e := bcrypt.GenerateFromPassword([]byte(in.Password), bcrypt.DefaultCost)
		if e != nil {
			fail(w, 500, "password error")
			return
		}
		v := store.User{ID: store.ID(), Username: in.Username, Admin: in.Admin, Quota: in.Quota, Created: time.Now()}
		if e = a.s.CreateUser(v, string(h)); e != nil {
			fail(w, 409, "username already exists or database unavailable")
			return
		}
		a.s.AddAudit(u.ID, "user.create", v.ID, "")
		writeJSON(w, v)
	case "PATCH":
		var in struct {
			ID    string
			Quota int64 `json:"quota_bytes"`
		}
		if json.NewDecoder(http.MaxBytesReader(w, r.Body, 4096)).Decode(&in) != nil || in.ID == "" || in.Quota <= 0 {
			fail(w, 400, "positive quota and user ID required")
			return
		}
		user := a.userLocks.Acquire(in.ID)
		defer user.Release()
		result, err := a.s.DB.Exec("UPDATE users SET quota=? WHERE id=?", in.Quota, in.ID)
		if err != nil {
			fail(w, 500, "quota update failed")
			return
		}
		count, _ := result.RowsAffected()
		if count != 1 {
			fail(w, 404, "user not found")
			return
		}
		a.s.AddAudit(u.ID, "user.quota", in.ID, strconv.FormatInt(in.Quota, 10))
		writeJSON(w, map[string]bool{"ok": true})
	default:
		fail(w, 405, "method not allowed")
	}
}
func (a *API) resetPassword(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Cache-Control", "no-store")
	if r.Method != http.MethodPost {
		fail(w, 405, "method not allowed")
		return
	}
	u, _, err := a.user(r)
	if err != nil {
		fail(w, 401, "authentication required")
		return
	}
	if !u.Admin {
		fail(w, 403, "administrator required")
		return
	}
	var in struct{ ID, Password string }
	decoder := json.NewDecoder(http.MaxBytesReader(w, r.Body, 4096))
	if decoder.Decode(&in) != nil || decoder.Decode(new(any)) != io.EOF || in.ID == "" || len(in.Password) < 12 || len(in.Password) > 72 {
		fail(w, 400, "user ID and password 12–72 bytes required")
		return
	}
	hash, err := bcrypt.GenerateFromPassword([]byte(in.Password), bcrypt.DefaultCost)
	if err != nil {
		fail(w, 500, "password error")
		return
	}
	// Login must not issue a session using a hash read before this reset.
	a.authLoginMu.Lock()
	defer a.authLoginMu.Unlock()
	u, _, err = a.user(r)
	if err != nil {
		fail(w, 401, "authentication required")
		return
	}
	if !u.Admin {
		fail(w, 403, "administrator required")
		return
	}
	tx, err := a.s.DB.BeginTx(r.Context(), nil)
	if err != nil {
		fail(w, 500, "password reset failed")
		return
	}
	defer tx.Rollback()
	var username string
	err = tx.QueryRowContext(r.Context(), "SELECT username FROM users WHERE id=?", in.ID).Scan(&username)
	if err == sql.ErrNoRows {
		fail(w, 404, "user not found")
		return
	}
	if err == nil {
		_, err = tx.ExecContext(r.Context(), "UPDATE users SET pass_hash=? WHERE id=?", string(hash), in.ID)
	}
	if err == nil {
		_, err = tx.ExecContext(r.Context(), "DELETE FROM auth_refresh WHERE sid IN (SELECT id FROM sessions WHERE uid=?)", in.ID)
	}
	if err == nil {
		_, err = tx.ExecContext(r.Context(), "DELETE FROM sessions WHERE uid=?", in.ID)
	}
	if err == nil {
		_, err = tx.ExecContext(r.Context(), "DELETE FROM auth_failures WHERE username=?", username)
	}
	if err == nil {
		_, err = tx.ExecContext(r.Context(), "INSERT INTO audit(uid,action,target,detail,at) VALUES(?,?,?,?,?)", u.ID, "user.reset_password", in.ID, "", time.Now().Unix())
	}
	if err == nil {
		err = tx.Commit()
	}
	if err != nil {
		fail(w, 500, "password reset failed")
		return
	}
	writeJSON(w, map[string]bool{"ok": true, "reauthenticate": u.ID == in.ID})
}

func (a *API) audit(w http.ResponseWriter, r *http.Request) {
	u, _, e := a.user(r)
	if e != nil {
		fail(w, 401, "authentication required")
		return
	}
	if !u.Admin {
		fail(w, 403, "administrator required")
		return
	}
	if r.Method != "GET" {
		fail(w, 405, "method not allowed")
		return
	}
	rows, e := a.s.DB.Query("SELECT id,uid,action,target,detail,at FROM audit ORDER BY id DESC LIMIT 500")
	if e != nil {
		fail(w, 500, "database error")
		return
	}
	defer rows.Close()
	out := []map[string]any{}
	for rows.Next() {
		var id, at int64
		var uid, action, target, detail string
		if rows.Scan(&id, &uid, &action, &target, &detail, &at) != nil {
			fail(w, 500, "database error")
			return
		}
		out = append(out, map[string]any{"id": id, "user_id": uid, "action": action, "target": target, "detail": detail, "created_at": time.Unix(at, 0)})
	}
	if err := rows.Err(); err != nil {
		fail(w, 500, "database error")
		return
	}
	writeJSON(w, out)
}