package httpserver

import (
	"context"
	"encoding/json"
	"net/http"
	"strconv"
	"strings"

	"github.com/krow/krow-backend/go-api/internal/authctx"
	"github.com/krow/krow-backend/go-api/internal/domain"
	"github.com/krow/krow-backend/go-api/internal/repo"
)

// The current-user endpoints. See api-contract.md §9.
//
// "Current" now means the user behind the session cookie, resolved by the
// authentication middleware and read from the request context. Before Phase 3C
// it meant the organization's oldest user, found with ORDER BY created_date
// LIMIT 1 — a placeholder that was correct only because there was exactly one.

// preferenceColumns maps the frontend's camelCase preference keys onto their
// columns. Anything not listed here lives in user_preferences.extra — which is
// where customSkills and customAgents, every account-authored definition,
// currently are.
var preferenceColumns = map[string]string{
	"owliverDefault": "owliver_default",
	"compactDensity": "compact_density",
	"emailDigest":    "email_digest",
}

// userColumns is the projection for a user record.
const userColumns = `id::text AS id, legacy_id, full_name, email::text AS email,
	role, account_type, status,
	to_char(created_date AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS.MS"Z"') AS created_date,
	to_char(updated_date AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS.MS"Z"') AS updated_date`

// updatableUserFields are the only columns PATCH /me may write, and this map is
// the entire authority on that: a column absent from it cannot be reached by
// this endpoint at all, whatever the request body says.
//
// full_name    the Profile page's display-name field.
// account_type which product surface the person is looking at — Employer or
//
//	Talent. Layout.jsx writes it when the viewer switches.
//	Explicitly NOT an authorization field (Phase 3B decision 1); it
//	is a display attribute, and users.role is what authorizes.
//
// Everything else is server-owned. `role` used to be in this map, which meant
// any signed-in user could promote themselves to admin with a one-line PATCH
// the moment sessions existed. It was harmless while there was no
// authentication and a live privilege-escalation path the instant there was.
// See serverOwnedUserFields.
var updatableUserFields = map[string]string{
	"full_name":    "text",
	"account_type": "text",
}

// serverOwnedUserFields are the fields a user must never write about
// themselves, listed by name so an attempt can be recognised and logged rather
// than silently dropped in with every other unknown key.
//
// They are ignored, not rejected: a PATCH body is "whichever fields the caller
// sent", the endpoint has always ignored what it does not own, and the response
// returns the user as they actually are — so a caller who asks for a role
// change gets a 200 whose body shows the role unchanged. What is new is that
// the attempt is now visible in the log, because a client asking to change its
// own role is worth knowing about even when the answer is no.
var serverOwnedUserFields = map[string]bool{
	"id":            true,
	"org_id":        true,
	"role":          true,
	"password_hash": true,
	"status":        true,
	"email":         true,
	"legacy_id":     true,
	"last_login_at": true,
	"created_date":  true,
	"updated_date":  true,
}

func (s *Server) routeMe(mux *http.ServeMux) int {
	mux.HandleFunc("GET /api/v1/me", s.handleMeGet)
	mux.HandleFunc("PATCH /api/v1/me", s.handleMePatch)
	mux.HandleFunc("GET /api/v1/me/preferences", s.handlePreferencesGet)
	mux.HandleFunc("PATCH /api/v1/me/preferences", s.handlePreferencesPatch)
	return 4
}

// userRecord reads one user by id, with preferences embedded.
//
// Embedded rather than a sibling resource because krowHooks.js:42 reads
// `user?.preferences` straight off the object returned by auth.me().
//
// The id is always one this server resolved from a session — never a value off
// the request. There is deliberately no variant of this function that takes an
// identifier from a caller.
func (s *Server) userRecord(ctx context.Context, q repo.Querier, userID string) (domain.Record, error) {
	rows, err := q.Query(ctx,
		`SELECT `+userColumns+` FROM users WHERE id = $1::uuid`,
		userID)
	if err != nil {
		return nil, domain.Internal(err)
	}
	defer rows.Close()

	fields := rows.FieldDescriptions()
	if !rows.Next() {
		// Unreachable in practice: the middleware just read this row to build
		// the identity. Reported rather than papered over.
		return nil, domain.NotFound("User", "current")
	}
	vals, err := rows.Values()
	if err != nil {
		return nil, domain.Internal(err)
	}
	user := make(domain.Record, len(fields)+1)
	for i, f := range fields {
		user[string(f.Name)] = vals[i]
	}
	rows.Close()

	prefs, err := s.preferences(ctx, q, user["id"].(string))
	if err != nil {
		return nil, err
	}
	user["preferences"] = prefs
	return user, nil
}

// preferences reads the three columns plus the extra blob, flattened into the
// single camelCase object the frontend expects.
func (s *Server) preferences(ctx context.Context, q repo.Querier, userID string) (map[string]any, error) {
	var owliver, compact, digest bool
	var extra []byte
	err := q.QueryRow(ctx,
		`SELECT owliver_default, compact_density, email_digest, extra
		   FROM user_preferences WHERE user_id = $1::uuid`, userID).
		Scan(&owliver, &compact, &digest, &extra)

	out := map[string]any{}
	if err != nil {
		// No row yet is a legitimate state: the defaults below are the schema's.
		return map[string]any{"owliverDefault": true, "compactDensity": false, "emailDigest": true}, nil
	}
	if len(extra) > 0 {
		_ = json.Unmarshal(extra, &out)
	}
	out["owliverDefault"] = owliver
	out["compactDensity"] = compact
	out["emailDigest"] = digest
	return out, nil
}

func (s *Server) handleMeGet(w http.ResponseWriter, r *http.Request) {
	id, err := authctx.MustFrom(r.Context())
	if err != nil {
		writeError(w, s.log, domain.Internal(err))
		return
	}
	user, err := s.userRecord(r.Context(), s.db.Pool, id.UserID)
	if err != nil {
		writeError(w, s.log, err)
		return
	}
	writeRecord(w, http.StatusOK, user)
}

func (s *Server) handleMePatch(w http.ResponseWriter, r *http.Request) {
	id, err := authctx.MustFrom(r.Context())
	if err != nil {
		writeError(w, s.log, domain.Internal(err))
		return
	}
	body, err := decodeBody(r)
	if err != nil {
		writeError(w, s.log, err)
		return
	}

	// The row to update is the session's user. Note what is NOT consulted: the
	// body may contain an "id", and it is ignored — writing to whichever user
	// the caller names is the whole of the vulnerability this avoids.
	sets, args := []string{}, []any{id.UserID}
	details := map[string]string{}
	for k, v := range body {
		if k == "preferences" {
			details[k] = "update preferences through /api/v1/me/preferences"
			continue
		}
		pgType, ok := updatableUserFields[k]
		if !ok {
			if serverOwnedUserFields[k] {
				s.log.Warn("ignored an attempt to write a server-owned user field",
					"field", k, "user_id", id.UserID, "session_id", id.SessionID)
			}
			continue // server-owned, or simply not a column: ignored either way
		}
		str, isStr := v.(string)
		if !isStr {
			details[k] = "expected a string"
			continue
		}
		args = append(args, str)
		sets = append(sets, k+" = $"+strconv.Itoa(len(args))+"::"+pgType)
	}
	if len(details) > 0 {
		writeError(w, s.log, domain.Validation("User payload is not valid", details))
		return
	}

	if len(sets) > 0 {
		// Every column name in `sets` came from updatableUserFields, which is a
		// literal map in this file. No identifier here is caller-supplied; the
		// values are all bind parameters.
		q := "UPDATE users SET " + strings.Join(sets, ", ") + ", updated_date = now() WHERE id = $1::uuid"
		if _, err := s.db.Pool.Exec(r.Context(), q, args...); err != nil {
			writeError(w, s.log, domain.Internal(err))
			return
		}
	}

	user, err := s.userRecord(r.Context(), s.db.Pool, id.UserID)
	if err != nil {
		writeError(w, s.log, err)
		return
	}
	writeRecord(w, http.StatusOK, user)
}

func (s *Server) handlePreferencesGet(w http.ResponseWriter, r *http.Request) {
	id, err := authctx.MustFrom(r.Context())
	if err != nil {
		writeError(w, s.log, domain.Internal(err))
		return
	}
	prefs, err := s.preferences(r.Context(), s.db.Pool, id.UserID)
	if err != nil {
		writeError(w, s.log, err)
		return
	}
	writeJSON(w, http.StatusOK, envelope{Data: prefs})
}

// handlePreferencesPatch shallow-merges the supplied keys and returns the whole
// merged object, matching auth.updatePreferences().
func (s *Server) handlePreferencesPatch(w http.ResponseWriter, r *http.Request) {
	id, err := authctx.MustFrom(r.Context())
	if err != nil {
		writeError(w, s.log, domain.Internal(err))
		return
	}
	body, err := decodeBody(r)
	if err != nil {
		writeError(w, s.log, err)
		return
	}
	userID := id.UserID
	current, err := s.preferences(r.Context(), s.db.Pool, userID)
	if err != nil {
		writeError(w, s.log, err)
		return
	}

	merged := current
	if merged == nil {
		merged = map[string]any{}
	}
	details := map[string]string{}
	for k, v := range body {
		if _, isColumn := preferenceColumns[k]; isColumn {
			if _, ok := v.(bool); !ok {
				details[k] = "expected a boolean"
				continue
			}
		}
		merged[k] = v
	}
	if len(details) > 0 {
		writeError(w, s.log, domain.Validation("preferences payload is not valid", details))
		return
	}

	// Split the merged object back into its columns and the extra blob.
	extra := map[string]any{}
	for k, v := range merged {
		if _, isColumn := preferenceColumns[k]; !isColumn {
			extra[k] = v
		}
	}
	extraJSON, err := json.Marshal(extra)
	if err != nil {
		writeError(w, s.log, domain.Validation("preferences are not encodable as JSON", nil))
		return
	}

	_, err = s.db.Pool.Exec(r.Context(),
		`INSERT INTO user_preferences (user_id, owliver_default, compact_density, email_digest, extra, updated_date)
		 VALUES ($1::uuid, $2::boolean, $3::boolean, $4::boolean, $5::jsonb, now())
		 ON CONFLICT (user_id) DO UPDATE SET
		   owliver_default = EXCLUDED.owliver_default,
		   compact_density = EXCLUDED.compact_density,
		   email_digest    = EXCLUDED.email_digest,
		   extra           = EXCLUDED.extra,
		   updated_date    = now()`,
		userID, truthy(merged["owliverDefault"], true), truthy(merged["compactDensity"], false),
		truthy(merged["emailDigest"], true), extraJSON)
	if err != nil {
		writeError(w, s.log, domain.Internal(err))
		return
	}

	prefs, err := s.preferences(r.Context(), s.db.Pool, userID)
	if err != nil {
		writeError(w, s.log, err)
		return
	}
	writeJSON(w, http.StatusOK, envelope{Data: prefs})
}

func truthy(v any, fallback bool) bool {
	if b, ok := v.(bool); ok {
		return b
	}
	return fallback
}