package cameras

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"github.com/loyaly/behavision-agent/pkg/bridge"
	"github.com/loyaly/behavision-agent/pkg/config"
)

// EngineClient talks to the recognition engine on this PC's loopback.
type EngineClient struct {
	Base     string
	User     string
	Password string
	// Creds re-reads the engine's generated credential when one is rejected.
	// Without it a fresh install is 401 for the life of the process: the agent
	// starts the engine, and the engine writes its credential file seconds
	// after the agent has already read (and failed to find) it.
	Creds  *config.Creds
	Client *http.Client
}

func NewEngineClient(base, user, password string) *EngineClient {
	return &EngineClient{
		Base: strings.TrimRight(base, "/"), User: user, Password: password,
		// Generous, because adding a camera makes the engine dial it, and a
		// wrong address takes the full RTSP timeout to fail. Shorter than that
		// and every genuinely-bad camera looks like an engine fault instead.
		Client: &http.Client{Timeout: 30 * time.Second},
	}
}

func (e *EngineClient) do(ctx context.Context, method, path string, body, out any) error {
	var rdr io.Reader
	if body != nil {
		b, err := json.Marshal(body)
		if err != nil {
			return err
		}
		rdr = bytes.NewReader(b)
	}
	req, err := http.NewRequestWithContext(ctx, method, e.Base+path, rdr)
	if err != nil {
		return err
	}
	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	user, pass := e.User, e.Password
	if e.Creds != nil {
		user, pass = e.Creds.Get()
	}
	if user != "" {
		req.SetBasicAuth(user, pass)
	}
	resp, err := e.Client.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode == http.StatusUnauthorized && e.Creds != nil && e.Creds.Refresh() {
		// The engine generated its credential after we last looked. Read it
		// and try once more rather than failing for the life of the process.
		resp.Body.Close()
		return e.do(ctx, method, path, body, out)
	}
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		// The engine's message, not just a status. "camera stored but failed to
		// start: connection refused" is something an operator can act on;
		// "500" is not, and this string ends up in the agent log a support
		// engineer reads.
		msg, _ := io.ReadAll(io.LimitReader(resp.Body, 2048))
		return fmt.Errorf("engine %s: %s", resp.Status, strings.TrimSpace(string(msg)))
	}
	if out == nil {
		return nil
	}
	return json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(out)
}

func (e *EngineClient) List(ctx context.Context) ([]Local, error) {
	var out []Local
	return out, e.do(ctx, http.MethodGet, "/api/cameras", nil, &out)
}

func (e *EngineClient) Add(ctx context.Context, cam Local) error {
	return e.do(ctx, http.MethodPost, "/api/cameras", cam, nil)
}

func (e *EngineClient) Update(ctx context.Context, id string, cam Local) error {
	// The engine takes the id from the path on PATCH and refuses it in the
	// body, so it is cleared here rather than at the call site.
	cam.ID = ""
	return e.do(ctx, http.MethodPatch, "/api/cameras/"+url.PathEscape(id), cam, nil)
}

func (e *EngineClient) Remove(ctx context.Context, id string) error {
	return e.do(ctx, http.MethodDelete, "/api/cameras/"+url.PathEscape(id), nil, nil)
}

// Snapshot fetches the most recent frame the engine holds.
//
// Not a fresh capture: the engine already keeps the latest frame in memory for
// its own MJPEG stream, so this costs a memory copy rather than a camera round
// trip. A camera that has not produced a frame yet answers 503, which is a
// normal state on a just-added camera and not an error worth logging loudly.
func (e *EngineClient) Snapshot(ctx context.Context, id string) ([]byte, error) {
	return e.Frame(ctx, id, 0, 0)
}

// Frame fetches the latest frame, optionally re-encoded smaller.
//
// The live relay asks for ~640 px at quality 60 - about a third the bytes of
// the full frame - because it sends several a second up a shop's uplink, where
// the snapshot sends one a minute and can afford the detail. The engine does
// the re-encode: it already has OpenCV open and the frame in memory, and
// shipping a scaler into the agent to redo that would be the same work twice.
func (e *EngineClient) Frame(ctx context.Context, id string, width, quality int) ([]byte, error) {
	q := url.Values{}
	if width > 0 {
		q.Set("width", strconv.Itoa(width))
	}
	if quality > 0 {
		q.Set("quality", strconv.Itoa(quality))
	}
	target := e.Base + "/api/cameras/" + url.PathEscape(id) + "/frame.jpg"
	if len(q) > 0 {
		target += "?" + q.Encode()
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, target, nil)
	if err != nil {
		return nil, err
	}
	if e.User != "" {
		req.SetBasicAuth(e.User, e.Password)
	}
	resp, err := e.Client.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("engine %s", resp.Status)
	}
	// Bounded. A frame is tens of kilobytes; anything near this cap means
	// something other than a JPEG is on the other end.
	return io.ReadAll(io.LimitReader(resp.Body, 8<<20))
}

// CloudClient talks to head office with this agent's own token.
type CloudClient struct {
	Base   string
	Token  string
	Client *http.Client
	// Upload is the existing image path: the server mints a presigned URL and
	// the agent PUTs to it. Reused rather than reimplemented, so a shop PC
	// still never holds bucket credentials — the reason that path exists.
	Upload func(ctx context.Context, jpeg []byte) (string, error)
}

func NewCloudClient(base, token string) *CloudClient {
	return &CloudClient{
		Base: strings.TrimRight(base, "/"), Token: token,
		Client: &http.Client{Timeout: 20 * time.Second},
	}
}

func (c *CloudClient) do(ctx context.Context, method, path string, body, out any) error {
	if c.Token == "" {
		// An unclaimed PC. Said plainly, because this is the normal state
		// between installing the software and typing an enrolment code, and it
		// must not read as a fault in the log.
		return fmt.Errorf("this PC is not claimed by a company yet")
	}
	var rdr io.Reader
	if body != nil {
		b, err := json.Marshal(body)
		if err != nil {
			return err
		}
		rdr = bytes.NewReader(b)
	}
	req, err := http.NewRequestWithContext(ctx, method, c.Base+path, rdr)
	if err != nil {
		return err
	}
	req.Header.Set("Authorization", "Bearer "+c.Token)
	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	resp, err := c.Client.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return fmt.Errorf("head office: %s", resp.Status)
	}
	if out == nil || resp.StatusCode == http.StatusNoContent {
		return nil
	}
	return json.NewDecoder(io.LimitReader(resp.Body, 4<<20)).Decode(out)
}

func (c *CloudClient) Desired(ctx context.Context) ([]Desired, error) {
	var body struct {
		Cameras []Desired `json:"cameras"`
	}
	if err := c.do(ctx, http.MethodGet, "/api/agent/cameras", nil, &body); err != nil {
		return nil, err
	}
	return body.Cameras, nil
}

func (c *CloudClient) Report(ctx context.Context, rep Report) error {
	return c.do(ctx, http.MethodPost, "/api/agent/cameras", rep, nil)
}

func (c *CloudClient) UploadSnapshot(ctx context.Context, jpeg []byte) (string, error) {
	if c.Upload == nil {
		return "", fmt.Errorf("images are not enabled for this deployment")
	}
	return c.Upload(ctx, jpeg)
}

// PutSnapshot gets a camera's latest frame to head office by whichever route
// that deployment has.
//
// The bucket first: a presigned PUT goes straight to object storage and never
// passes through the API, which is what makes it the right route at estate
// scale. When there is no bucket the picture goes to the server itself, which
// stores one row per camera. Without this second route head office reported
// "This system is not storing images" for every camera forever, on the screen
// whose entire job is to show the camera.
//
// The returned key is empty for the direct route - there is no object to name -
// and the server records the picture as it stores it, so the state report has
// nothing to carry.
func (c *CloudClient) PutSnapshot(ctx context.Context, cameraID string, jpeg []byte) (string, error) {
	if c.Upload != nil {
		key, err := c.Upload(ctx, jpeg)
		if err == nil {
			return key, nil
		}
		// A bucket that is configured here but disabled at the server is the
		// ordinary case on a self-hosted install: fall through rather than
		// giving up, and let the direct route decide.
		if !isImagesDisabled(err) {
			return "", err
		}
	}
	return "", c.putSnapshotDirect(ctx, cameraID, jpeg)
}

func (c *CloudClient) putSnapshotDirect(ctx context.Context, cameraID string, jpeg []byte) error {
	req, err := http.NewRequestWithContext(ctx, http.MethodPut,
		c.Base+"/api/agent/cameras/"+url.PathEscape(cameraID)+"/snapshot",
		bytes.NewReader(jpeg))
	if err != nil {
		return err
	}
	req.Header.Set("Authorization", "Bearer "+c.Token)
	req.Header.Set("Content-Type", "image/jpeg")
	resp, err := c.Client.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return fmt.Errorf("head office: %s", resp.Status)
	}
	return nil
}

// isImagesDisabled recognises the server saying it has no object storage.
//
// A sentinel, not a string match on the message: this decides whether to take a
// completely different route, and getting it wrong from prose that somebody
// later rewords would silently stop every camera picture in the estate.
func isImagesDisabled(err error) bool {
	return errors.Is(err, bridge.ErrImagesOff)
}

// ---------------------------------------------------------------- probing

// Test opens the candidate stream once, without saving it.
//
// The engine does this as a sync handler in its threadpool because
// cv2.VideoCapture blocks hard, and it checks TCP reachability first - so a
// wrong address, which is the single most likely thing anybody types, answers
// in milliseconds rather than the ~75 s an FFmpeg connect takes to give up.
func (e *EngineClient) Test(ctx context.Context, cam Local) (TestResult, error) {
	var out TestResult
	// A generous ceiling: the engine's own deadline is 12 s for the frame plus
	// 3 s to connect, and cutting it off earlier would report a timeout of our
	// own making as if it were the camera's.
	ctx, cancel := context.WithTimeout(ctx, 45*time.Second)
	defer cancel()
	return out, e.do(ctx, http.MethodPost, "/api/cameras/test", cam, &out)
}

// Placement runs the engine's commissioning watch and returns its report whole.
//
// Polled rather than awaited: the engine starts the watch and answers
// immediately, so the run survives this request being retried, and the report
// arrives with `running: true` until it does not.
func (e *EngineClient) Placement(ctx context.Context, cameraID string, seconds int) (
	map[string]any, error) {

	path := "/api/cameras/" + url.PathEscape(cameraID) + "/commission"
	var report map[string]any
	if err := e.do(ctx, http.MethodPost, path,
		map[string]any{"seconds": seconds}, &report); err != nil {
		return nil, err
	}

	deadline := time.Now().Add(time.Duration(seconds+20) * time.Second)
	for time.Now().Before(deadline) {
		select {
		case <-ctx.Done():
			return report, ctx.Err()
		case <-time.After(2 * time.Second):
		}
		var latest map[string]any
		if err := e.do(ctx, http.MethodGet, path, nil, &latest); err != nil {
			// Keep the last good report rather than losing the whole run to
			// one failed poll - the engine may simply have been busy.
			continue
		}
		report = latest
		if running, _ := latest["running"].(bool); !running {
			return report, nil
		}
	}
	return report, nil
}

// ---------------------------------------------------------------- check jobs

func (c *CloudClient) Pending(ctx context.Context) ([]Job, error) {
	var body struct {
		Checks []Job `json:"checks"`
	}
	if err := c.do(ctx, http.MethodGet, "/api/agent/checks", nil, &body); err != nil {
		return nil, err
	}
	return body.Checks, nil
}

func (c *CloudClient) Submit(ctx context.Context, res Result) error {
	return c.do(ctx, http.MethodPost, "/api/agent/checks", res, nil)
}