// 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"
	"strings"
	"sync"
	"time"
)

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

type Request struct {
	ID     string `json:"id"`
	Method string `json:"method"`
	// Herdr's JSON-RPC decoder requires params to be present, including for
	// parameterless calls such as ping. Encode nil as an explicit JSON null.
	Params any `json:"params"`
}
type Response struct {
	ID     string          `json:"id"`
	Result json.RawMessage `json:"result"`
	Error  *struct {
		Code    string `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
	panes   map[string]string
}

type WorktreeInfo struct {
	Path string `json:"path"`
}

type worktreeResponse struct {
	Path     string       `json:"path"`
	Worktree WorktreeInfo `json:"worktree"`
	RootPane struct {
		PaneID string `json:"pane_id"`
		Agent  string `json:"agent"`
	} `json:"root_pane"`
	Workspace struct {
		RootPane struct {
			PaneID string `json:"pane_id"`
		} `json:"root_pane"`
	} `json:"workspace"`
}

func New(path string) *Client {
	return &Client{Path: path, Timeout: 10 * time.Second, panes: map[string]string{}}
}
func (c *Client) conn() (net.Conn, error) {
	if c.dial != nil {
		return c.dial()
	}
	network := "unix"
	if strings.Contains(c.Path, "://") || (strings.Contains(c.Path, ":") && !strings.HasPrefix(c.Path, "/")) {
		network = "tcp"
	}
	return net.DialTimeout(network, 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 params == nil {
		params = map[string]any{}
	}
	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 json.RawMessage `json:"protocol"`
	Version  json.RawMessage `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 != "" {
		var text string
		if err := json.Unmarshal(p.Protocol, &text); err != nil {
			text = string(p.Protocol)
		}
		if text != want {
			return fmt.Errorf("%w: want %s, got %s", ErrProtocol, want, text)
		}
	}
	return nil
}

type Session struct {
	PaneID   string `json:"pane_id"`
	Worktree string `json:"worktree"`
	Harness  string `json:"harness"`
	HerdrID  string `json:"herdr_id,omitempty"`
	// SessionFile is the filesystem path to the harness's own session/
	// transcript state (a Claude Code transcript, a Codex rollout, ...).
	// ClaudeUsage/CodexUsage/OpenCodeUsage read *this*, never the herdr pane
	// id — occupancy is a property of the harness's session state, not of
	// the pane multiplexing it. Left empty until resolved (see
	// CLIAdapter.Occupancy), since the file may not exist yet immediately
	// after lease.
	SessionFile string `json:"session_file,omitempty"`
	// TaskFileSHA is the sha256 of the worktree's TASK.md at the time this
	// session's lease was created — the immutable-spec hash continuity's
	// pickup validation compares against on the next rotation (§6.2).
	TaskFileSHA string `json:"task_file_sha,omitempty"`
	// HandoffRequested is set once rotate() has prompted the agent to write
	// its §6.1 handoff (HandoffFile) — avoids re-sending the same prompt
	// every tick while Release keeps waiting for the file to appear.
	HandoffRequested bool `json:"handoff_requested,omitempty"`
	// ConventionsHash is continuity.ConventionsHash of the project's shared
	// *.md docs (AGENTS.md/CLAUDE.md/VOCAB.md) at the time this session was
	// last notified of (or started with) their content — §6.3's staleness
	// tracking lives at the orchestra layer, never trusted from the agent's
	// cached view.
	ConventionsHash string `json:"conventions_hash,omitempty"`
}

func (c *Client) Prompt(ctx context.Context, pane, text string, wait time.Duration) error {
	p := map[string]any{"target": pane, "text": text}
	if wait > 0 {
		p["wait"] = map[string]any{"until": []string{"idle"}, "timeout_ms": wait.Milliseconds()}
	}
	return c.Call(ctx, "agent.prompt", p, nil)
}
func (c *Client) Worktree(ctx context.Context, cwd, path, branch string) (string, error) {
	var r worktreeResponse
	// Protocol 17 requires exactly one of path or branch. Use the explicit
	// path so the worker owns the checkout location; herdr manages the branch
	// associated with that worktree.
	p := map[string]any{"cwd": cwd, "path": path}
	e := c.Call(ctx, "worktree.create", p, &r)
	if e != nil && strings.Contains(strings.ToLower(e.Error()), "already exists") {
		e = c.Call(ctx, "worktree.open", map[string]any{"cwd": cwd, "path": path}, &r)
	}
	if e != nil {
		return "", e
	}
	if r.RootPane.PaneID != "" {
		c.mu.Lock()
		c.panes[path] = r.RootPane.PaneID
		c.mu.Unlock()
	}
	if r.Path != "" {
		return r.Path, nil
	}
	return r.Worktree.Path, nil
}

func (c *Client) StartAgent(ctx context.Context, cwd, path, branch, harness, taskID string) (Session, error) {
	c.mu.Lock()
	paneID := c.panes[path]
	c.mu.Unlock()
	if paneID == "" {
		return Session{}, fmt.Errorf("herdr: no pane recorded for worktree %s", path)
	}
	var s Session
	if err := c.Call(ctx, "agent.start", map[string]any{
		"pane_id": paneID,
		"kind":    harness,
		"name":    harness,
		"args":    []string{},
	}, &s); err != nil {
		if !strings.Contains(strings.ToLower(err.Error()), "already") {
			return Session{}, err
		}
	}
	s.PaneID = paneID
	s.Worktree = path
	s.Harness = harness
	return s, nil
}

// HeadSHA returns the current commit of a worktree. The rotation path uses
// this to populate TaskReleased.anchor_sha without trusting the adapter's
// opaque handoff-ref return value.
func HeadSHA(root string) (string, error) {
	out, err := exec.Command("git", "-C", root, "rev-parse", "HEAD").Output()
	if err != nil {
		return "", err
	}
	sha := string(out)
	if len(sha) > 0 && sha[len(sha)-1] == '\n' {
		sha = sha[:len(sha)-1]
	}
	if len(sha) != 40 {
		return "", fmt.Errorf("herdr: unexpected HEAD output %q", sha)
	}
	return sha, nil
}

// 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
}