// 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"
	"regexp"
	"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
	agents  map[string]string // pane ID -> machine-global agent name
}

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{}, agents: 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"`
	AgentName string `json:"agent_name,omitempty"`
	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"`
	// SessionID is the harness-native identity when its usage is stored in a
	// database rather than a transcript. OpenCode's SQLite session ID is kept
	// here so rotation never guesses "the newest session" after a restart.
	SessionID string `json:"session_id,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"`
	// HandoffReason is selected by the coordinator when it asks for the
	// semantic report. The checkout worker, rather than the harness, copies
	// it into the canonical handoff it seals at release time.
	HandoffReason string `json:"handoff_reason,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"`
}

// bootDeadline bounds the retry loops below. Freshly created panes/agents
// have been observed (live, 2026-07-28) to reject the very next call for a
// range of different transient reasons as herdr finishes bringing them up —
// "not an available shell", "not an active named agent", "target ... not
// found" — a new wording each time a prior one got fixed. There is no other
// legitimate reason a call against state orchestra itself just created would
// fail immediately, so these loops retry any error rather than pattern-match
// an open-ended and apparently still-growing set of herdr wordings, bounded
// by wall-clock time rather than attempt count so a slow-booting pane still
// gets the same real budget as a fast-failing one.
const (
	bootRetryWindow = 15 * time.Second
	bootRetryDelay  = 500 * time.Millisecond

	// agentAttachWindow/agentAttachPoll bound StartAgent's post-success
	// confirmation poll (B13, found live 2026-07-28): agent.start can return
	// no error while never actually starting an agent, observed on two of
	// three back-to-back leases — the pane's agent_status stayed "unknown"
	// after 2+ minutes of polling, with no error surfaced anywhere. A
	// legitimate attach has been observed taking "well over a minute", so
	// this window is deliberately longer than bootRetryWindow.
	claudeTrustObserveWindow = 15 * time.Second
	claudeTrustClearWindow   = 15 * time.Second
	claudeTrustPoll          = 500 * time.Millisecond
)

var (
	agentAttachWindow = 90 * time.Second
	agentAttachPoll   = 2 * time.Second
)

type paneStatus struct {
	Agent       string `json:"agent"`
	AgentStatus string `json:"agent_status"`
}

// paneGetResponse mirrors herdr's pane.get result envelope. The pane fields
// are not returned at the top level: the result is {"type":"pane_info",
// "pane": {...}}. Keeping that wrapper explicit prevents a successful
// agent.start from being falsely reported as unattached.
type paneGetResponse struct {
	Pane paneStatus `json:"pane"`
}

type paneReadResponse struct {
	Read struct {
		Text string `json:"text"`
	} `json:"read"`
}

// paneAgentAttached reports whether herdr's own view of the pane shows a
// real agent bound to it, rather than trusting agent.start's return value.
func (c *Client) paneAgentAttached(ctx context.Context, paneID string) (bool, error) {
	var p paneGetResponse
	if err := c.Call(ctx, "pane.get", map[string]any{"pane_id": paneID}, &p); err != nil {
		return false, err
	}
	return p.Pane.Agent != "" && p.Pane.AgentStatus != "" && p.Pane.AgentStatus != "unknown", nil
}

func (c *Client) paneText(ctx context.Context, paneID string) (string, error) {
	var p paneReadResponse
	if err := c.Call(ctx, "pane.read", map[string]any{"pane_id": paneID, "source": "recent"}, &p); err != nil {
		return "", err
	}
	return p.Read.Text, nil
}

func claudeWorkspaceTrustPrompt(text string) bool {
	return strings.Contains(text, "Accessing workspace:") && strings.Contains(text, "Yes, I trust this folder")
}

// confirmClaudeWorkspaceTrust accepts only Claude Code's exact workspace
// trust prompt. Orchestra creates its worktrees from registered project
// repositories, so leaving this interactive would make every new worktree
// permanently unattended-ineligible. It deliberately does not accept any
// other Claude confirmation (in particular bypass-permissions mode).
func (c *Client) confirmClaudeWorkspaceTrust(ctx context.Context, paneID string) error {
	deadline := time.Now().Add(claudeTrustObserveWindow)
	accepted := false
	for {
		text, err := c.paneText(ctx, paneID)
		if err == nil && claudeWorkspaceTrustPrompt(text) {
			if !accepted {
				if err := c.Call(ctx, "pane.send_text", map[string]any{"pane_id": paneID, "text": "1\n"}, nil); err != nil {
					return fmt.Errorf("herdr: accept Claude workspace trust for pane %s: %w", paneID, err)
				}
				accepted = true
				deadline = time.Now().Add(claudeTrustClearWindow)
			}
		} else if accepted {
			return nil
		}
		if time.Now().After(deadline) {
			if accepted {
				return fmt.Errorf("herdr: Claude workspace trust prompt did not clear for pane %s", paneID)
			}
			return nil
		}
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-time.After(claudeTrustPoll):
		}
	}
}

func (c *Client) Prompt(ctx context.Context, pane, text string, wait time.Duration) error {
	var status paneGetResponse
	if err := c.Call(ctx, "pane.get", map[string]any{"pane_id": pane}, &status); err != nil {
		return fmt.Errorf("herdr: inspect pane before prompt: %w", err)
	}
	if strings.EqualFold(status.Pane.AgentStatus, "blocked") {
		return fmt.Errorf("herdr: refusing prompt to blocked pane %s", pane)
	}
	transcript, err := c.paneText(ctx, pane)
	if err != nil {
		return fmt.Errorf("herdr: inspect pane text before prompt: %w", err)
	}
	if permissionPrompt(transcript) {
		return fmt.Errorf("herdr: refusing prompt while pane %s shows a permission dialog", pane)
	}
	c.mu.Lock()
	target := c.agents[pane]
	c.mu.Unlock()
	if target == "" {
		// Session records created before unique agent names were introduced
		// used the pane as target; retain that compatibility path.
		target = pane
	}
	p := map[string]any{"target": target, "text": text}
	if wait > 0 {
		p["wait"] = map[string]any{"until": []string{"idle"}, "timeout_ms": wait.Milliseconds()}
	}
	callCtx := ctx
	var cancel context.CancelFunc
	if wait > 0 {
		if d, ok := ctx.Deadline(); !ok || time.Until(d) < wait+5*time.Second {
			callCtx, cancel = context.WithTimeout(ctx, wait+5*time.Second)
			defer cancel()
		}
	}
	// A transport failure after writing is ambiguous: herdr may already have
	// delivered the UI-changing request, so never resend it. A JSON-RPC
	// protocol error, however, is herdr's explicit rejection before it acted
	// (notably its short post-start readiness window); that is safe to retry
	// for the bounded boot window.
	deadline := time.Now().Add(bootRetryWindow)
	for {
		err := c.Call(callCtx, "agent.prompt", p, nil)
		if err == nil {
			return nil
		}
		if !errors.Is(err, ErrProtocol) || time.Now().After(deadline) {
			return fmt.Errorf("herdr: prompt delivery is uncertain; not retrying: %w", err)
		}
		select {
		case <-callCtx.Done():
			return fmt.Errorf("herdr: prompt delivery is uncertain; not retrying: %w", callCtx.Err())
		case <-time.After(bootRetryDelay):
		}
	}
}

// BindAgent restores the pane-to-agent routing from a persisted Session.
func (c *Client) BindAgent(pane, agent string) {
	if pane == "" || agent == "" {
		return
	}
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.agents == nil {
		c.agents = map[string]string{}
	}
	c.agents[pane] = agent
}

func permissionPrompt(text string) bool {
	text = strings.ToLower(text)
	return strings.Contains(text, "permission required") || strings.Contains(text, "approval required") || strings.Contains(text, "waiting for approval")
}
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
	deadline := time.Now().Add(bootRetryWindow)
	var err error
	for {
		s = Session{}
		err = c.Call(ctx, "agent.start", map[string]any{
			"pane_id": paneID,
			"kind":    harness,
			"name":    agentName(harness, taskID),
			"args":    harnessStartArgs(harness),
		}, &s)
		if err == nil {
			break
		}
		if strings.Contains(strings.ToLower(err.Error()), "already") {
			err = nil
			break
		}
		if time.Now().After(deadline) {
			return Session{}, err
		}
		select {
		case <-ctx.Done():
			return Session{}, ctx.Err()
		case <-time.After(bootRetryDelay):
		}
	}
	if err != nil {
		return Session{}, err
	}
	// B13: agent.start's success does not mean an agent actually attached.
	// Confirm via pane.get before declaring the lease started, so a silent
	// no-op surfaces as an observable error (TaskBlocked) instead of leaving
	// the task leased against a pane that will never produce a session.
	attachDeadline := time.Now().Add(agentAttachWindow)
	for {
		ok, statusErr := c.paneAgentAttached(ctx, paneID)
		if statusErr == nil && ok {
			break
		}
		if time.Now().After(attachDeadline) {
			if statusErr != nil {
				return Session{}, fmt.Errorf("herdr: agent.start reported success for pane %s but confirming attach failed: %w", paneID, statusErr)
			}
			return Session{}, fmt.Errorf("herdr: agent.start reported success for pane %s but no agent attached within %s", paneID, agentAttachWindow)
		}
		select {
		case <-ctx.Done():
			return Session{}, ctx.Err()
		case <-time.After(agentAttachPoll):
		}
	}
	if strings.EqualFold(harness, "claude") {
		if err := c.confirmClaudeWorkspaceTrust(ctx, paneID); err != nil {
			return Session{}, err
		}
	}
	s.PaneID = paneID
	s.Worktree = path
	s.Harness = harness
	s.AgentName = agentName(harness, taskID)
	c.BindAgent(paneID, s.AgentName)
	return s, nil
}

var invalidAgentName = regexp.MustCompile(`[^a-z0-9_-]+`)

func agentName(harness, taskID string) string {
	prefix := map[string]string{"opencode": "oc", "claude": "cl", "codex": "cx"}[strings.ToLower(harness)]
	if prefix == "" {
		prefix = "agent"
	}
	id := strings.Trim(invalidAgentName.ReplaceAllString(strings.ToLower(taskID), "-"), "-_")
	if id == "" {
		id = "session"
	}
	name := prefix + "-" + id
	if len(name) <= 32 {
		return name
	}
	// Keeping only the leading task-id characters made distinct long task
	// IDs collide in herdr's machine-global name namespace. Reserve a stable
	// digest suffix so truncation remains bounded *and* task-specific.
	sum := sha256.Sum256([]byte(taskID))
	const suffixLen = 8
	keep := 32 - len(prefix) - 1 - 1 - suffixLen // prefix + "-" + stem + "-" + digest
	return prefix + "-" + strings.TrimRight(id[:keep], "-_") + "-" + fmt.Sprintf("%x", sum[:])[:suffixLen]
}

// harnessStartArgs stays empty for Claude: --dangerously-skip-permissions
// introduces a separate first-run disclaimer. StartAgent instead acknowledges
// only the registered-worktree trust prompt after Claude is running.
func harnessStartArgs(harness string) []string {
	return []string{}
}

// 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
}