// Package herdr contains the small, protocol-oriented execution seam used by
// the orchestration layer. It deliberately does not shell out to a harness.
package herdr

import (
	"bufio"
	"context"
	"crypto/sha256"
	"encoding/json"
	"errors"
	"fmt"
	"net"
	"os"
	"os/exec"
	"path/filepath"
	"sync"
	"time"
)

var ErrProtocol = errors.New("herdr protocol error")

type Request struct {
	ID     string `json:"id"`
	Method string `json:"method"`
	Params any    `json:"params,omitempty"`
}
type Response struct {
	ID     string          `json:"id"`
	Result json.RawMessage `json:"result"`
	Error  *struct {
		Code    int    `json:"code"`
		Message string `json:"message"`
	} `json:"error,omitempty"`
}
type Client struct {
	Path    string
	Timeout time.Duration
	dial    func() (net.Conn, error)
	mu      sync.Mutex
	next    uint64
}

func New(path string) *Client { return &Client{Path: path, Timeout: 10 * time.Second} }
func (c *Client) conn() (net.Conn, error) {
	if c.dial != nil {
		return c.dial()
	}
	return net.DialTimeout("unix", c.Path, c.Timeout)
}
func (c *Client) Call(ctx context.Context, method string, params any, out any) error {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.next++
	id := fmt.Sprint(c.next)
	cn, err := c.conn()
	if err != nil {
		return err
	}
	defer cn.Close()
	if d, ok := ctx.Deadline(); ok {
		_ = cn.SetDeadline(d)
	} else if c.Timeout > 0 {
		_ = cn.SetDeadline(time.Now().Add(c.Timeout))
	}
	if err = json.NewEncoder(cn).Encode(Request{ID: id, Method: method, Params: params}); err != nil {
		return err
	}
	var r Response
	if err = json.NewDecoder(bufio.NewReader(cn)).Decode(&r); err != nil {
		return err
	}
	if r.Error != nil {
		return fmt.Errorf("%w: %s", ErrProtocol, r.Error.Message)
	}
	if out != nil && len(r.Result) > 0 {
		return json.Unmarshal(r.Result, out)
	}
	return nil
}

type PingResult struct {
	Protocol string `json:"protocol"`
	Version  string `json:"version"`
}

func (c *Client) Ping(ctx context.Context) (PingResult, error) {
	var p PingResult
	err := c.Call(ctx, "ping", nil, &p)
	return p, err
}
func (c *Client) CheckProtocol(ctx context.Context, want string) error {
	p, e := c.Ping(ctx)
	if e != nil {
		return e
	}
	if want != "" && p.Protocol != want {
		return fmt.Errorf("%w: want %s, got %s", ErrProtocol, want, p.Protocol)
	}
	return nil
}

type Session struct {
	PaneID   string `json:"pane_id"`
	Worktree string `json:"worktree"`
	Harness  string `json:"harness"`
}

func (c *Client) Prompt(ctx context.Context, pane, text string, wait time.Duration) error {
	p := map[string]any{"pane_id": pane, "prompt": text, "wait": map[string]any{"until": "turn_end", "timeout_ms": wait.Milliseconds()}}
	return c.Call(ctx, "agent.prompt", p, nil)
}
func (c *Client) Worktree(ctx context.Context, path, branch string) (string, error) {
	var r struct {
		Path string `json:"path"`
	}
	e := c.Call(ctx, "worktree.create", map[string]string{"path": path, "branch": branch}, &r)
	return r.Path, e
}

// AnchorValid checks the split-then-close safety condition without trusting a
// predecessor's prose. dirty maps contain path -> expected SHA-256.
func AnchorValid(root, sha string, dirty map[string]string) error {
	out, e := exec.Command("git", "-C", root, "rev-parse", "HEAD").Output()
	if e != nil {
		return e
	}
	if string(out) != sha+"\n" {
		return fmt.Errorf("anchor: HEAD mismatch")
	}
	for p, want := range dirty {
		b, e := os.ReadFile(filepath.Join(root, p))
		if e != nil {
			return e
		}
		h := sha256.Sum256(b)
		if fmt.Sprintf("%x", h) != want {
			return fmt.Errorf("anchor: %s changed", p)
		}
	}
	return nil
}