package main

import (
	"bufio"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"git.eidonix.com/eidonix/cletus-plugins/sdk/manifest"
)

type message struct {
	ID       string          `json:"id,omitempty"`
	ParentID string          `json:"parent_id,omitempty"`
	Method   string          `json:"method,omitempty"`
	Params   json.RawMessage `json:"params,omitempty"`
	Result   json.RawMessage `json:"result,omitempty"`
	Error    *struct {
		Message string `json:"message"`
	} `json:"error,omitempty"`
}

// testHost runs a worker and answers its host calls the way Cletus does,
// within the plugin's declared permissions. Every host call is logged.
type testHost struct {
	plugin       *manifest.Plugin
	filesDir     string // the folder the user "opened"
	workspaceDir string // backs the one simulated shared folder ("" = none)
	dataDir      string
	edit         bool
	capabilities map[string]bool
	log          io.Writer

	cmd     *exec.Cmd
	stdin   io.WriteCloser
	writeMu sync.Mutex
	mu      sync.Mutex
	pending map[string]chan message
	next    int
	exited  chan struct{}
}

const testWorkspaceID = "ws:00000000-0000-0000-0000-000000000001"

func (h *testHost) start(bin string) error {
	if err := os.MkdirAll(h.dataDir, 0o755); err != nil {
		return err
	}
	h.cmd = exec.Command(bin)
	h.cmd.Dir = h.dataDir
	h.cmd.Env = []string{"CLETUS_PLUGIN_ID=" + h.plugin.ID, "CLETUS_PLUGIN_DATA=" + h.dataDir}
	for _, name := range []string{"HOME", "USERPROFILE", "PATH", "TMPDIR", "TEMP", "TMP", "LANG", "SystemRoot"} {
		if v, ok := os.LookupEnv(name); ok {
			h.cmd.Env = append(h.cmd.Env, name+"="+v)
		}
	}
	h.cmd.Stderr = prefixWriter{w: h.log, prefix: "worker  "}
	var err error
	if h.stdin, err = h.cmd.StdinPipe(); err != nil {
		return err
	}
	stdout, err := h.cmd.StdoutPipe()
	if err != nil {
		return err
	}
	h.pending = map[string]chan message{}
	h.exited = make(chan struct{})
	if err := h.cmd.Start(); err != nil {
		return err
	}
	go h.read(stdout)
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	var hs struct {
		APIVersion int `json:"api_version"`
	}
	if err := h.call(ctx, "plugin.handshake", nil, &hs); err != nil {
		return fmt.Errorf("handshake: %w", err)
	}
	if hs.APIVersion != 1 {
		return fmt.Errorf("handshake: the worker speaks api_version %d; Cletus needs 1", hs.APIVersion)
	}
	return nil
}

func (h *testHost) stop() {
	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	_ = h.call(ctx, "plugin.shutdown", nil, nil)
	cancel()
	h.stdin.Close()
	select {
	case <-h.exited:
	case <-time.After(2 * time.Second):
		_ = h.cmd.Process.Kill()
		<-h.exited
	}
}

func (h *testHost) read(stdout io.Reader) {
	defer close(h.exited)
	defer func() { _ = h.cmd.Wait() }()
	sc := bufio.NewScanner(stdout)
	sc.Buffer(make([]byte, 64<<10), 64<<20+1)
	for sc.Scan() {
		var m message
		if err := json.Unmarshal(sc.Bytes(), &m); err != nil {
			fmt.Fprintf(h.log, "host    the worker wrote something that isn't a message (is it printing to stdout?): %.200s\n", sc.Text())
			continue
		}
		switch {
		case m.Method == "$/cancel":
		case m.Method != "":
			go h.serve(m)
		default:
			h.mu.Lock()
			ch := h.pending[m.ID]
			delete(h.pending, m.ID)
			h.mu.Unlock()
			if ch != nil {
				ch <- m
			}
		}
	}
	h.mu.Lock()
	for id, ch := range h.pending {
		close(ch)
		delete(h.pending, id)
	}
	h.mu.Unlock()
}

func (h *testHost) send(m message) error {
	data, err := json.Marshal(m)
	if err != nil {
		return err
	}
	h.writeMu.Lock()
	defer h.writeMu.Unlock()
	_, err = h.stdin.Write(append(data, '\n'))
	return err
}

func (h *testHost) call(ctx context.Context, method string, params, out any) error {
	var raw json.RawMessage
	if params != nil {
		var err error
		if raw, err = json.Marshal(params); err != nil {
			return err
		}
	}
	ch := make(chan message, 1)
	h.mu.Lock()
	h.next++
	id := fmt.Sprintf("h%d", h.next)
	h.pending[id] = ch
	h.mu.Unlock()
	if err := h.send(message{ID: id, Method: method, Params: raw}); err != nil {
		return fmt.Errorf("the worker has stopped: %w", err)
	}
	select {
	case reply, ok := <-ch:
		if !ok {
			return errors.New("the worker stopped before answering")
		}
		if reply.Error != nil {
			return errors.New(reply.Error.Message)
		}
		if out != nil {
			return json.Unmarshal(reply.Result, out)
		}
		return nil
	case <-ctx.Done():
		cancelID, _ := json.Marshal(id)
		_ = h.send(message{Method: "$/cancel", Params: cancelID})
		return ctx.Err()
	}
}

// serve answers one host call from the worker.
func (h *testHost) serve(m message) {
	result, err := h.answer(m.Method, m.Params)
	reply := message{ID: m.ID}
	outcome := "ok"
	if err != nil {
		reply.Error = &struct {
			Message string `json:"message"`
		}{err.Error()}
		outcome = "error: " + err.Error()
	} else {
		reply.Result, _ = json.Marshal(result)
	}
	fmt.Fprintf(h.log, "host    %s %s → %s\n", m.Method, clip(string(m.Params), 200), outcome)
	if m.ID != "" {
		_ = h.send(reply)
	}
}

func clip(s string, n int) string {
	if len(s) > n {
		return s[:n] + "…"
	}
	return s
}

func (h *testHost) answer(method string, raw json.RawMessage) (any, error) {
	if ok, need := h.plugin.Allowed(method); !ok {
		if need != "" {
			return nil, fmt.Errorf("this plugin is not allowed to use %s; it needs the %s permission", method, need)
		}
		return nil, fmt.Errorf("unknown plugin host operation %q", method)
	}
	var p struct {
		Path, Key, Workspace, Prefix, Name, Data, ContentType string
		TTL                                                   int
		Args                                                  []any
	}
	_ = json.Unmarshal(raw, &p)
	switch method {
	case "host.auth.has_capability":
		var c struct{ Capability string }
		_ = json.Unmarshal(raw, &c)
		return map[string]bool{"granted": h.capabilities[c.Capability]}, nil
	case "host.auth.whoami":
		return map[string]any{"key_id": 1, "name": "Test User", "org": "Test Organization", "org_id": "00000000-0000-0000-0000-000000000000"}, nil
	case "host.files.resolve":
		return h.resolve(p.Path)
	case "host.files.can_write":
		path, err := h.resolve(p.Path)
		if err != nil {
			path, err = h.within(p.Path)
		}
		return err == nil && h.edit && path != "", nil
	case "host.event":
		if !strings.HasPrefix(p.Name, h.plugin.ID+":") {
			return nil, errors.New("plugin event is not permitted")
		}
		return nil, nil
	case "host.screen.open":
		return nil, errors.New("screens aren't available yet")
	case "host.dialog.open", "host.dialog.folder", "host.dialog.save", "host.dialog.message":
		return nil, errors.New("the test host has no dialogs; pass paths as tool arguments while testing")
	case "host.plugin.call":
		return nil, errors.New("the test host runs no other plugins")
	case "host.data.publish":
		path, err := h.inData(p.Path)
		if err != nil {
			return nil, err
		}
		if p.TTL < 1 || p.TTL > 3600 {
			return nil, errors.New("artifact ttl must be 1 to 3600 seconds")
		}
		return map[string]string{"token": "test-token", "url": "file://" + filepath.ToSlash(path), "expiresAt": time.Now().Add(time.Duration(p.TTL) * time.Second).UTC().Format(time.RFC3339)}, nil
	case "host.data.revoke":
		return nil, nil
	case "host.data.leases":
		return 0, nil
	case "host.data.remove":
		path, err := h.inData(p.Path)
		if err != nil {
			return nil, err
		}
		if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
			return nil, err
		}
		return nil, nil
	case "host.agent.start", "host.agent.status", "host.agent.cancel":
		return nil, errors.New("background runs aren't available in the test host")
	}
	if strings.HasPrefix(method, "host.workspace.") {
		return h.workspace(method, p.Workspace, p.Key, p.Prefix, p.Path, p.Data)
	}
	return nil, fmt.Errorf("unknown plugin host operation %q", method)
}

// resolve answers host.files.resolve: a path inside the opened folder.
func (h *testHost) resolve(path string) (string, error) {
	resolved, err := h.within(path)
	if err != nil {
		return "", err
	}
	if _, err := os.Stat(resolved); err != nil {
		return "", fmt.Errorf("%s does not exist", path)
	}
	return resolved, nil
}

func (h *testHost) within(path string) (string, error) {
	if path == "" {
		return "", errors.New("path is empty")
	}
	if !filepath.IsAbs(path) {
		path = filepath.Join(h.filesDir, path)
	}
	path = filepath.Clean(path)
	if !inside(h.filesDir, path) {
		return "", fmt.Errorf("%s is outside the files the user opened", path)
	}
	return path, nil
}

func (h *testHost) inData(path string) (string, error) {
	if !filepath.IsAbs(path) {
		path = filepath.Join(h.dataDir, path)
	}
	path = filepath.Clean(path)
	if !inside(h.dataDir, path) {
		return "", errors.New("the path must be inside the plugin's data folder")
	}
	return path, nil
}

func inside(root, path string) bool {
	rel, err := filepath.Rel(root, path)
	return err == nil && rel != ".." && !strings.HasPrefix(rel, ".."+string(filepath.Separator)) && !filepath.IsAbs(rel)
}