package api

import (
	"context"
	"database/sql"
	"errors"
	"net/http"
	"strconv"
	"strings"
	"time"

	"git.ryuvia.com/niklas/terdut-server/internal/models"
	"github.com/go-chi/chi/v5"
)

// serviceAccountKeyPrefix marks a service-account key visibly, in logs and at
// a glance, distinct from a user's own personal API key. It carries no
// meaning to the server itself — the hash is looked up the same way either
// kind of key is — it exists entirely for whoever is reading a log line or an
// audit trail.
const serviceAccountKeyPrefix = "tdsa_"

// randomServiceAccountToken is randomToken with serviceAccountKeyPrefix on the
// raw value, hashed as a whole: the prefix is not a fixed header stripped
// before hashing, it is part of the secret, the same as if it had been
// generated that long to begin with.
func randomServiceAccountToken() (raw, hash string, err error) {
	body, _, err := randomToken()
	if err != nil {
		return "", "", err
	}
	raw = serviceAccountKeyPrefix + body
	return raw, hashToken(raw), nil
}

// callerIsAdmin reports whether the caller is a signed-in human system
// administrator. A service account never is, by design (SERVICE-ACCOUNTS.md):
// account and user management stays human-only, service accounts included.
func callerIsAdmin(ctx context.Context) bool {
	u, ok := userFromContext(ctx)
	return ok && u.IsAdmin
}

// callerOwnsTeam reports whether the caller is a human owner of teamID. Built
// on callerRole/ctxTeams like requireTeamOwner, but without writing a
// response: callers here need to combine it with other ways of being
// allowed, not stop at the first no.
func callerOwnsTeam(ctx context.Context, teamID int64) bool {
	role, ok := callerRole(ctx, teamID)
	return ok && role == models.RoleOwner
}

// handleCreateServiceAccount creates a service account and mints its first
// key. Who may do this depends on scope: an instance-scoped account (which
// can in turn create a team and a team-scoped account for it) is system
// administration's own reach extended to automation, so only a human admin
// grants one. A team-scoped account is that team's owner's reach, so a human
// admin, the target team's own human owner, or an existing instance-scoped
// service account (minting itself a narrower credential for a team it just
// created) may create one.
func handleCreateServiceAccount(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var req struct {
			Name   string `json:"name"`
			Scope  string `json:"scope"`
			TeamID int64  `json:"team_id"`
		}
		if err := decodeJSON(r, &req); err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid request body"))
			return
		}
		req.Name = strings.TrimSpace(req.Name)
		if req.Name == "" {
			respond(w, http.StatusBadRequest, errResp("name is required"))
			return
		}
		if req.Scope != models.ServiceAccountScopeInstance && req.Scope != models.ServiceAccountScopeTeam {
			respond(w, http.StatusBadRequest, errResp("scope must be instance or team"))
			return
		}
		if req.Scope == models.ServiceAccountScopeTeam && req.TeamID == 0 {
			respond(w, http.StatusBadRequest, errResp("team_id is required for a team-scoped account"))
			return
		}
		if req.Scope == models.ServiceAccountScopeInstance && req.TeamID != 0 {
			respond(w, http.StatusBadRequest, errResp("team_id must not be set for an instance-scoped account"))
			return
		}

		allowed := callerIsAdmin(r.Context())
		if !allowed && req.Scope == models.ServiceAccountScopeTeam {
			allowed = callerOwnsTeam(r.Context(), req.TeamID) || isInstanceServiceAccount(r.Context())
		}
		if !allowed {
			respond(w, http.StatusForbidden, errResp("team owner, system administrator, or instance-scoped service account access required"))
			return
		}

		var callerUserID *int64
		if u, ok := userFromContext(r.Context()); ok {
			id := u.ID
			callerUserID = &id
		}
		var teamID *int64
		if req.Scope == models.ServiceAccountScopeTeam {
			teamID = &req.TeamID
		}

		var sa models.ServiceAccount
		var created int64
		if err := db.QueryRowContext(r.Context(), `
			INSERT INTO service_accounts (name, scope, team_id, created_by)
			VALUES ($1, $2, $3, $4)
			RETURNING id, name, scope, team_id, created_by, created_at`,
			req.Name, req.Scope, teamID, callerUserID,
		).Scan(&sa.ID, &sa.Name, &sa.Scope, &sa.TeamID, &sa.CreatedBy, &created); err != nil {
			if isUniqueViolation(err) {
				respond(w, http.StatusConflict, errResp("a service account with that name already exists"))
				return
			}
			// The only foreign key that can fail here is team_id: an
			// instance-scoped caller is not otherwise checked against it
			// (callerOwnsTeam already proved it exists for a human owner).
			respond(w, http.StatusBadRequest, errResp("unknown team_id"))
			return
		}
		sa.CreatedAt = time.Unix(created, 0).UTC()

		key, err := mintServiceAccountKey(r.Context(), db, sa.ID, "initial")
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		respond(w, http.StatusCreated, map[string]any{"service_account": sa, "key": key})
	}
}

// mintServiceAccountKey inserts one key for an existing account and returns
// it with its raw value populated — the one moment that value exists outside
// the request that generated it.
func mintServiceAccountKey(ctx context.Context, db *sql.DB, serviceAccountID int64, name string) (models.ServiceAccountKey, error) {
	raw, hash, err := randomServiceAccountToken()
	if err != nil {
		return models.ServiceAccountKey{}, err
	}
	var key models.ServiceAccountKey
	var created int64
	if err := db.QueryRowContext(ctx, `
		INSERT INTO service_account_keys (service_account_id, key_hash, name)
		VALUES ($1, $2, $3)
		RETURNING id, service_account_id, name, created_at`,
		serviceAccountID, hash, name,
	).Scan(&key.ID, &key.ServiceAccountID, &key.Name, &created); err != nil {
		return models.ServiceAccountKey{}, err
	}
	key.CreatedAt = time.Unix(created, 0).UTC()
	key.Key = raw
	return key, nil
}

func fetchServiceAccount(ctx context.Context, db *sql.DB, id int64) (models.ServiceAccount, error) {
	var sa models.ServiceAccount
	var created int64
	err := db.QueryRowContext(ctx,
		"SELECT id, name, scope, team_id, created_by, created_at FROM service_accounts WHERE id = $1", id,
	).Scan(&sa.ID, &sa.Name, &sa.Scope, &sa.TeamID, &sa.CreatedBy, &created)
	if err != nil {
		return sa, err
	}
	sa.CreatedAt = time.Unix(created, 0).UTC()
	return sa, nil
}

// callerMayManageServiceAccount reports whether the caller may mint or revoke
// a key on sa: a system administrator, that team-scoped account's own human
// owner, or the account rotating its own credential — which is not a
// privilege escalation, the same reasoning requireSelfOrAdmin already rests
// on for a user's own API keys.
func callerMayManageServiceAccount(ctx context.Context, sa models.ServiceAccount) bool {
	if callerIsAdmin(ctx) {
		return true
	}
	if sa.TeamID != nil && callerOwnsTeam(ctx, *sa.TeamID) {
		return true
	}
	if self, ok := serviceAccountFromContext(ctx); ok && self.id == sa.ID {
		return true
	}
	return false
}

func serviceAccountParam(w http.ResponseWriter, r *http.Request) (int64, bool) {
	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
	if err != nil {
		respond(w, http.StatusBadRequest, errResp("invalid service account id"))
		return 0, false
	}
	return id, true
}

func handleCreateServiceAccountKey(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := serviceAccountParam(w, r)
		if !ok {
			return
		}
		sa, err := fetchServiceAccount(r.Context(), db, id)
		if errors.Is(err, sql.ErrNoRows) {
			respond(w, http.StatusNotFound, errResp("service account not found"))
			return
		}
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if !callerMayManageServiceAccount(r.Context(), sa) {
			respond(w, http.StatusForbidden, errResp("team owner, system administrator, or the account itself may rotate its key"))
			return
		}

		var req struct {
			Name string `json:"name"`
		}
		if err := decodeJSON(r, &req); err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid request body"))
			return
		}
		if req.Name == "" {
			respond(w, http.StatusBadRequest, errResp("name is required"))
			return
		}

		key, err := mintServiceAccountKey(r.Context(), db, sa.ID, req.Name)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		respond(w, http.StatusCreated, key)
	}
}

func handleDeleteServiceAccountKey(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, ok := serviceAccountParam(w, r)
		if !ok {
			return
		}
		sa, err := fetchServiceAccount(r.Context(), db, id)
		if errors.Is(err, sql.ErrNoRows) {
			respond(w, http.StatusNotFound, errResp("service account not found"))
			return
		}
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if !callerMayManageServiceAccount(r.Context(), sa) {
			respond(w, http.StatusForbidden, errResp("team owner, system administrator, or the account itself may revoke its key"))
			return
		}
		keyID, err := strconv.ParseInt(chi.URLParam(r, "keyID"), 10, 64)
		if err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid key id"))
			return
		}

		res, err := db.ExecContext(r.Context(),
			"DELETE FROM service_account_keys WHERE id = $1 AND service_account_id = $2", keyID, sa.ID)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if n, _ := res.RowsAffected(); n == 0 {
			respond(w, http.StatusNotFound, errResp("key not found"))
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
}

// handleListServiceAccounts lists every service account, or looks one up by
// its exact name with ?name=. The name lookup is open to any authenticated
// caller, human or service account: it returns no key material, and it is
// what lets a service account find its own account on the 403 that follows a
// second POST — the self-registration pattern SERVICE-ACCOUNTS.md describes.
// Listing everything, with no filter, stays administrator-only.
func handleListServiceAccounts(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		name := strings.TrimSpace(r.URL.Query().Get("name"))
		if name == "" && !callerIsAdmin(r.Context()) {
			respond(w, http.StatusForbidden, errResp("administrator access required to list every service account; pass ?name= to look up one by name"))
			return
		}

		query := "SELECT id, name, scope, team_id, created_by, created_at FROM service_accounts"
		var args []any
		if name != "" {
			query += " WHERE name = $1"
			args = append(args, name)
		}
		query += " ORDER BY id"

		rows, err := db.QueryContext(r.Context(), query, args...)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		defer rows.Close()

		accounts := []models.ServiceAccount{}
		for rows.Next() {
			var sa models.ServiceAccount
			var created int64
			if err := rows.Scan(&sa.ID, &sa.Name, &sa.Scope, &sa.TeamID, &sa.CreatedBy, &created); err != nil {
				respond(w, http.StatusInternalServerError, errResp("internal error"))
				return
			}
			sa.CreatedAt = time.Unix(created, 0).UTC()
			accounts = append(accounts, sa)
		}
		if err := rows.Err(); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		respond(w, http.StatusOK, accounts)
	}
}