package web

import (
	"context"
	"errors"
	"log/slog"
	"net/http"

	"github.com/a-h/templ"

	"gitea.d-ma.be/mathias/tapir/internal/adapters/store"
)

// Store is the read/write surface the web handlers depend on — a narrow port over
// the Postgres store (Clean Architecture: handlers depend on this interface, not
// the concrete *store.Store). *store.Store satisfies it; tests can substitute a
// fake without a database.
type Store interface {
	ListSummaries(ctx context.Context, userID string, limit int) ([]store.SummaryRow, error)
	GetSummaryByVideo(ctx context.Context, userID, videoID string) (*store.SummaryRow, error)
	ActionsFor(ctx context.Context, userID string, videoIDs []string) (map[string][]string, error)
	SetAction(ctx context.Context, userID, videoID, action string) error
	ClearAction(ctx context.Context, userID, videoID, action string) error
}

// App is the Stage-1 web surface: handlers over the store, gated by an Auth
// implementation (authentication) and a registration gate (which resolves the
// authenticated subject to its tapir user_id and stashes it per request). Every
// data handler scopes by that resolved id — CurrentUserID(r) — not by a single
// configured user (ADR-012, multi-user with enforced isolation).
type App struct {
	Store    Store
	Identity Identity
	Auth     Auth
	Log      *slog.Logger
	// Connect runs the web-initiated YouTube OAuth connect flow. Optional: when
	// nil (e.g. dev without YouTube client credentials), the /oauth/youtube/*
	// routes are not mounted.
	Connect *ConnectHandler
}

func (a *App) logger() *slog.Logger {
	if a.Log != nil {
		return a.Log
	}
	return slog.Default()
}

// Router wires the routes: /healthz (no auth) and /auth/* (the Auth impl's own
// endpoints) sit outside the guard; everything else is wrapped by
// Auth.Middleware. Go 1.22+ method+path patterns route directly.
func (a *App) Router() http.Handler {
	root := http.NewServeMux()
	root.HandleFunc("GET /healthz", a.handleHealthz)
	root.Handle("GET /static/", staticHandler())
	root.Handle("/auth/", a.Auth.Routes())

	app := http.NewServeMux()
	app.HandleFunc("GET /{$}", a.handleList)
	app.HandleFunc("GET /v/{videoId}", a.handleDetail)
	app.HandleFunc("POST /v/{videoId}/action", a.handleAction)
	app.HandleFunc("GET /register", a.handleRegisterForm)
	app.HandleFunc("POST /register", a.handleRegister)

	// Web-initiated YouTube connect (ADR-006). Gated like every app route, so
	// CurrentUserID is set and the connection binds to the authenticated user.
	if a.Connect != nil {
		app.HandleFunc("GET /oauth/youtube/connect", a.Connect.handleConnect)
		app.HandleFunc("GET /oauth/youtube/callback", a.Connect.handleCallback)
	}

	// Two layers: Auth.Middleware requires a Dex session (you must be logged in);
	// registrationGate requires a tapir user (else → /register) and stashes the
	// resolved user_id. /register lives inside the auth guard but is exempt from
	// the registration gate (you must be able to reach it before you have a user).
	root.Handle("/", a.Auth.Middleware(a.registrationGate(app)))
	return root
}

// handleHealthz is the unauthenticated liveness/readiness probe.
func (a *App) handleHealthz(w http.ResponseWriter, _ *http.Request) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	_, _ = w.Write([]byte("ok"))
}

// handleList renders the summary list, applying the channel/date filters from the
// query string. An HTMX request gets only the table fragment so the filter form
// can swap #summary-list in place; a plain request gets the full page.
func (a *App) handleList(w http.ResponseWriter, r *http.Request) {
	userID, ok := a.currentUserID(w, r)
	if !ok {
		return
	}
	q := r.URL.Query()
	f := Filter{
		Channel: q.Get("channel"),
		From:    q.Get("from"),
		To:      q.Get("to"),
	}

	rows, err := a.Store.ListSummaries(r.Context(), userID, 0)
	if err != nil {
		a.serverError(w, r, "list summaries", err)
		return
	}
	rows = f.apply(rows)

	if isHTMX(r) {
		a.render(w, r, summaryList(rows))
		return
	}
	a.render(w, r, ListPage(rows, f, takeFlash(w, r)))
}

// handleDetail renders one summary in full (highlights, takeaways, action group).
func (a *App) handleDetail(w http.ResponseWriter, r *http.Request) {
	userID, ok := a.currentUserID(w, r)
	if !ok {
		return
	}
	videoID := r.PathValue("videoId")
	row, err := a.Store.GetSummaryByVideo(r.Context(), userID, videoID)
	if errors.Is(err, store.ErrNotFound) {
		http.NotFound(w, r)
		return
	}
	if err != nil {
		a.serverError(w, r, "get summary", err)
		return
	}
	a.render(w, r, DetailPage(*row))
}

// handleAction toggles one action: re-clicking an active verb clears it, else it
// is set (the store enforces watched↔skipped exclusion atomically). It returns
// the refreshed button-group fragment for HTMX; without JS it redirects back to
// the detail page (POST→redirect→GET).
func (a *App) handleAction(w http.ResponseWriter, r *http.Request) {
	userID, ok := a.currentUserID(w, r)
	if !ok {
		return
	}
	videoID := r.PathValue("videoId")
	action := r.FormValue("action")
	if !isActionVerb(action) {
		http.Error(w, "unknown action", http.StatusBadRequest)
		return
	}

	current, err := a.Store.ActionsFor(r.Context(), userID, []string{videoID})
	if err != nil {
		a.serverError(w, r, "read actions", err)
		return
	}

	if actionSet(current[videoID])[action] {
		err = a.Store.ClearAction(r.Context(), userID, videoID, action)
	} else {
		err = a.Store.SetAction(r.Context(), userID, videoID, action)
	}
	if err != nil {
		a.serverError(w, r, "toggle action", err)
		return
	}

	updated, err := a.Store.ActionsFor(r.Context(), userID, []string{videoID})
	if err != nil {
		a.serverError(w, r, "read actions", err)
		return
	}

	if isHTMX(r) {
		a.render(w, r, ActionButtons(videoID, actionSet(updated[videoID])))
		return
	}
	http.Redirect(w, r, "/v/"+videoID, http.StatusSeeOther)
}

// currentUserID returns the tapir user_id the registration gate resolved for this
// request. Behind the gate it is always present; a miss means a handler was
// reached without scoping (a wiring bug), so it answers 500 and reports false.
func (a *App) currentUserID(w http.ResponseWriter, r *http.Request) (string, bool) {
	id, ok := CurrentUserID(r)
	if !ok {
		a.serverError(w, r, "current user", errNoCurrentUser)
	}
	return id, ok
}

// render writes a templ component as HTML. A render error is logged, not retried:
// headers may already be flushed, so there is nothing useful to send the client.
func (a *App) render(w http.ResponseWriter, r *http.Request, c templ.Component) {
	a.renderStatus(w, r, http.StatusOK, c)
}

// renderStatus writes a templ component as HTML with an explicit status code (the
// Content-Type must be set before WriteHeader, so this is the single place that
// orders them correctly).
func (a *App) renderStatus(w http.ResponseWriter, r *http.Request, status int, c templ.Component) {
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.WriteHeader(status)
	if err := c.Render(r.Context(), w); err != nil {
		a.logger().Error("render", "path", r.URL.Path, "err", err)
	}
}

func (a *App) serverError(w http.ResponseWriter, r *http.Request, op string, err error) {
	a.logger().Error("handler error", "op", op, "path", r.URL.Path, "err", err)
	http.Error(w, "internal error", http.StatusInternalServerError)
}

// isHTMX reports whether the request came from HTMX, which sets HX-Request: true.
func isHTMX(r *http.Request) bool {
	return r.Header.Get("HX-Request") == "true"
}