package handler

import (
	"crypto/rand"
	"math/big"
	"net/http"
	"net/mail"
	"strings"

	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
	"github.com/warmbly/warmbly/internal/api/middleware"
	"github.com/warmbly/warmbly/internal/errx"
	"github.com/warmbly/warmbly/internal/pkg/argon2"
	"github.com/warmbly/warmbly/internal/pkg/displayname"
)

// A tester account is one an operator hands to somebody outside the team: a
// vendor's reviewer during an OAuth verification, an auditor, a support
// engineer. It is an ordinary account with its own workspace, marked exempt
// from the emailed login code because the holder cannot read this instance's
// mail. That exemption is what makes it findable later, so the list below is
// the same set the instance check warns about.

type adminCreateTesterRequest struct {
	Email   string `json:"email"`
	OrgName string `json:"org_name"`
	Reason  string `json:"reason"`
	// OrgID joins the tester to a workspace that already exists instead of
	// minting an empty one. That is what a vendor's reviewer needs: an OAuth
	// verification is judged on the app doing real work, and a workspace with
	// no mailbox in it shows none of that. RoleID is then required, because
	// this is the one path that grants workspace access without anybody in
	// that workspace asking for it, and a default would be a permission
	// nobody chose.
	OrgID  *uuid.UUID `json:"organization_id"`
	RoleID *uuid.UUID `json:"role_id"`
}

type adminCreateTesterResponse struct {
	UserID uuid.UUID `json:"user_id"`
	Email  string    `json:"email"`
	OrgID  uuid.UUID `json:"organization_id"`
	// Joined reports whether the tester landed in an existing workspace rather
	// than one made for it, so the panel can say which and the operator is not
	// left guessing what they just handed out.
	Joined bool `json:"joined_existing"`
	// Password is returned once and never stored in a readable form. Losing it
	// means making another tester, which is cheap.
	Password string `json:"password"`
}

// testerPasswordAlphabet leaves out the characters that are misread when a
// password is copied by hand off a screen or out of a form.
const testerPasswordAlphabet = "abcdefghijkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789"

func testerPassword() (string, error) {
	const length = 20
	b := make([]byte, length)
	max := big.NewInt(int64(len(testerPasswordAlphabet)))
	for i := range b {
		n, err := rand.Int(rand.Reader, max)
		if err != nil {
			return "", err
		}
		b[i] = testerPasswordAlphabet[n.Int64()]
	}
	return "Tester-" + string(b), nil
}

// AdminCreateTester creates the account, its workspace and the exemption in
// one call, so an operator never has to reach for the CLI to let a reviewer in.
func (h *Handler) AdminCreateTester(c *gin.Context) {
	adminID := middleware.GetAdminUserID(c)
	if adminID == nil {
		errx.JSON(c, errx.ErrUnauthorized)
		return
	}

	var req adminCreateTesterRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		errx.JSON(c, errx.New(errx.BadRequest, "an email and a reason are required"))
		return
	}
	parsed, perr := mail.ParseAddress(strings.TrimSpace(req.Email))
	if perr != nil {
		errx.JSON(c, errx.New(errx.BadRequest, "that is not a valid email address"))
		return
	}
	reason := strings.TrimSpace(req.Reason)
	if reason == "" {
		errx.JSON(c, errx.New(errx.BadRequest, "a reason is required, so the account is answerable later"))
		return
	}
	if h.UserRepo == nil || h.OrganizationService == nil {
		errx.JSON(c, errx.New(errx.ServiceUnavailable, "account creation is not available on this instance"))
		return
	}

	if _, nerr := displayname.Validate("Workspace name", req.OrgName, displayname.Workspace, true); nerr != nil {
		errx.JSON(c, nerr)
		return
	}

	if req.OrgID != nil && req.RoleID == nil {
		errx.JSON(c, errx.New(errx.BadRequest, "joining an existing workspace needs a role, so the access granted is one somebody chose"))
		return
	}

	if existing, lerr := h.UserRepo.GetUserByEmail(c.Request.Context(), parsed.Address); lerr == nil && existing != nil {
		errx.JSON(c, errx.New(errx.BadRequest, "an account with that address already exists"))
		return
	}

	password, gerr := testerPassword()
	if gerr != nil {
		errx.JSON(c, errx.New(errx.Internal, "could not generate a password"))
		return
	}
	hash, herr := argon2.Hash(password)
	if herr != nil {
		errx.JSON(c, errx.New(errx.Internal, "could not hash the password"))
		return
	}

	// One transaction, so a failure cannot leave an account that holds no
	// exemption: that account would be invisible to the tester list,
	// un-retryable because the address was taken, and reachable by whoever
	// held the password.
	created, cerr := h.UserRepo.CreateExemptUser(c.Request.Context(), parsed, hash, reason, adminID)
	if cerr != nil {
		errx.JSON(c, errx.New(errx.Internal, "could not create the account"))
		return
	}

	// A tester joined to an existing workspace gets no workspace of its own on
	// purpose. Owning one would leave the reviewer a member of two, and the
	// dashboard only skips its workspace picker when there is exactly one, so
	// the first thing they would meet is a chooser naming an empty workspace.
	var orgID uuid.UUID
	joined := req.OrgID != nil
	if joined {
		member, merr := h.OrganizationService.AttachTester(c.Request.Context(), *req.OrgID, created.ID, *adminID, *req.RoleID)
		if merr != nil {
			h.undoHalfMadeTester(c, created.ID, merr)
			return
		}
		orgID = member.OrganizationID
	} else {
		orgName := strings.TrimSpace(req.OrgName)
		if orgName == "" {
			orgName = "Tester workspace"
		}
		org, oerr := h.OrganizationService.Create(c.Request.Context(), created.ID, orgName, "")
		if oerr != nil {
			h.undoHalfMadeTester(c, created.ID, oerr)
			return
		}
		orgID = org.ID
		if h.TrialService != nil {
			// Best effort: without it the workspace has no subscription row and
			// reads as unpaid, which is recoverable from the admin panel.
			_ = h.TrialService.StartFreeTrialWithOrg(c.Request.Context(), created.ID, org.ID)
		}
	}

	entry := map[string]any{
		"email": created.Email, "reason": reason, "organization_id": orgID.String(),
		"joined_existing": joined,
	}
	if joined {
		// The role is the whole of what this tester can reach, so it belongs in
		// the audit row rather than only in the members table it can be
		// changed out of later.
		entry["role_id"] = req.RoleID.String()
	}
	h.logTesterAction(c, *adminID, created.ID, "create_tester", entry)

	c.JSON(http.StatusOK, adminCreateTesterResponse{
		UserID:   created.ID,
		Email:    created.Email,
		OrgID:    orgID,
		Joined:   joined,
		Password: password,
	})
}

// undoHalfMadeTester removes an account whose workspace step failed. Leaving it
// would take the address without giving anybody anything: revoking the
// exemption does not free the address, and a retry fails the existing-email
// check, so the operator would have nowhere to go. The delete is guarded on the
// account holding no membership, so it cannot remove a tester that did join.
//
// The original error is what the operator sees, because a seat limit and a role
// that does not exist are both things they can fix and neither is a 500. Only a
// cleanup that itself fails changes the answer, since that is the one case
// where something was left behind.
func (h *Handler) undoHalfMadeTester(c *gin.Context, userID uuid.UUID, cause *errx.Error) {
	if derr := h.UserRepo.DeleteOrphanExemptUser(c.Request.Context(), userID); derr != nil {
		errx.JSON(c, errx.New(errx.Internal,
			cause.Message+"; the half-made account could not be removed either, and it is listed under Testers"))
		return
	}
	errx.JSON(c, cause)
}

// AdminListTesters returns every account holding a login-code exemption, which
// is the set an operator needs to review and prune.
func (h *Handler) AdminListTesters(c *gin.Context) {
	if h.UserRepo == nil {
		errx.JSON(c, errx.New(errx.ServiceUnavailable, "accounts are not available on this instance"))
		return
	}
	list, err := h.UserRepo.ListLoginCodeExempt(c.Request.Context())
	if err != nil {
		errx.JSON(c, errx.New(errx.Internal, "could not list tester accounts"))
		return
	}
	c.JSON(http.StatusOK, gin.H{"data": list})
}

// AdminRevokeTester drops the exemption. The account stays, so anything it
// created is still attributable; it simply stops bypassing the login code.
func (h *Handler) AdminRevokeTester(c *gin.Context) {
	adminID := middleware.GetAdminUserID(c)
	if adminID == nil {
		errx.JSON(c, errx.ErrUnauthorized)
		return
	}
	userID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		errx.JSON(c, errx.New(errx.BadRequest, "that is not a user id"))
		return
	}
	if h.UserRepo == nil {
		errx.JSON(c, errx.New(errx.ServiceUnavailable, "accounts are not available on this instance"))
		return
	}
	if err := h.UserRepo.SetLoginCodeExempt(c.Request.Context(), userID, false, "", nil); err != nil {
		errx.JSON(c, errx.New(errx.Internal, "could not revoke the exemption"))
		return
	}
	h.logTesterAction(c, *adminID, userID, "revoke_tester", nil)
	c.JSON(http.StatusOK, gin.H{"revoked": true})
}

func (h *Handler) logTesterAction(c *gin.Context, adminID, userID uuid.UUID, action string, details map[string]any) {
	if h.AdminService == nil {
		return
	}
	h.AdminService.LogAdminAction(c.Request.Context(), adminID, action, "user", &userID,
		details, c.ClientIP(), c.Request.UserAgent())
}