package herdr

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"orchestra/internal/continuity"
	"os"
	"path/filepath"
	"strings"
	"time"
)

// sha256sum returns the sha256 of a file, or nil if it can't be read — the
// caller compares against a known-good hex digest, so a nil/short mismatch
// naturally fails that comparison rather than needing its own error path.
func sha256sum(path string) []byte {
	b, err := os.ReadFile(path)
	if err != nil {
		return nil
	}
	sum := sha256.Sum256(b)
	return sum[:]
}

type Adapter interface {
	Lease(context.Context, string, string) (Session, error)
	Bootstrap(context.Context, Session, string) error
	Release(context.Context, Session) (string, error)
	Kill(context.Context, Session) error
	Occupancy(Session) (float64, error)
}

type WorktreeCreator interface {
	CreateWorktree(context.Context, string, string, string) (string, error)
}

// TurnBoundary is optional so older herdr deployments remain usable. A true
// result means the current harness turn has ended and handoff is safe.
type TurnBoundary interface {
	AtTurnBoundary(context.Context, Session) (bool, error)
}
type PaneExit interface {
	PaneExited(context.Context, Session) (bool, error)
}

// AgentStatus is a live, non-lifecycle status reported by herdr. Consumers
// must not infer task completion or release from it.
type AgentStatus interface {
	AgentStatus(context.Context, Session) (string, error)
}
type AgentBlocker interface {
	AgentBlocker(context.Context, Session) (string, error)
}
type PaneCapture interface {
	PaneCapture(context.Context, Session, string) (string, error)
}
type CLIAdapter struct {
	Client  *Client
	Harness string
	Window  int64
	Usage   func(string) (Usage, error)
	// CAS is where the agent-authored §6.1 handoff artifact is uploaded on
	// release. Nil disables Release (adapters built without one refuse
	// loudly rather than skip validation).
	CAS continuity.CAS
}

// HandoffFile is the convention the agent writes its §6.1 handoff to before
// stopping, mirroring the .orchestra-report.md convention B3 established for
// completion: the plane never invents a handoff, it only validates and
// uploads the one the agent wrote (herdr does not write handoffs, §6.1).
const HandoffFile = ".orchestra-handoff.json"

func (a CLIAdapter) CreateWorktree(ctx context.Context, repo, root, taskID string) (string, error) {
	path, err := a.Client.Worktree(ctx, repo, filepath.Join(root, taskID), "orchestra/"+taskID)
	if err != nil {
		return "", err
	}
	if path == "" {
		return "", fmt.Errorf("adapter: herdr returned empty worktree path")
	}
	return path, nil
}

func (a CLIAdapter) Lease(ctx context.Context, task, worktree string) (Session, error) {
	if a.Client == nil {
		return Session{}, fmt.Errorf("adapter: client required")
	}
	s, err := a.Client.StartAgent(ctx, worktree, worktree, "orchestra/"+task, a.Harness, task)
	if err != nil {
		return Session{}, err
	}
	if err := a.Client.Prompt(ctx, s.PaneID, fmt.Sprintf("Begin Orchestra task %s. Inspect the repository, understand the task context, and proceed with the requested work.", task), time.Minute); err != nil {
		return Session{}, err
	}
	return s, nil
}
// bootstrapPrompt implements the §6.2 pickup procedure: the plane has already
// run ValidatePickup before this is ever sent (Coordinator.Start blocks the
// task and never bootstraps on failure), so this prompt does not ask the
// agent to re-derive trust in the handoff — it orients the agent inside a
// checkout the plane has already certified, and tells it what NOT to touch.
const bootstrapPrompt = `You are picking up an in-progress Orchestra task (handoff ref %s).
This worktree's anchor and TASK.md have already been verified by the plane before you were started — you do not need to re-derive trust in them.
1. Re-read TASK.md at the worktree root. It is immutable; never edit it.
2. Run 'git log --stat -5' and 'git branch --show-current' in this worktree — the prior agent's uncommitted work was snapshotted onto a scratch branch with a descriptive commit message before rotation; that commit is the record of what it did and what's left.
3. Do not repeat work already recorded as done or as a dead end in that commit history.
4. Continue the task from there.`

func (a CLIAdapter) Bootstrap(ctx context.Context, s Session, ref string) error {
	return a.Client.Prompt(ctx, s.PaneID, fmt.Sprintf(bootstrapPrompt, ref), time.Minute)
}

// handoffPrompt is Phase 4 item 2's missing half (AUDIT.md): Release already
// validates and uploads a §6.1 handoff the agent wrote, but nothing ever told
// the agent that convention exists. rotate() sends this once occupancy crosses
// the hard threshold at a turn boundary, mirroring the .orchestra-report.md
// convention B3 established for completion — the plane still never invents a
// handoff, it only asks the agent to produce one, then validates it in Release.
const handoffPrompt = `Orchestra is about to rotate this task to a fresh session (context budget reached).
Before you stop, write a §6.1 handoff to ` + HandoffFile + ` at the worktree root, a JSON object with at least:
{"meta":{"id":"<any stable string for this handoff>"},"anchor":{"git_sha":"<current HEAD via git rev-parse HEAD>","branch":"<current branch>","dirty":[{"path":"<repo-relative path>","sha256":"<sha256 of its current contents>"}, ...for any uncommitted files]},"knowledge":{...whatever structured context the next agent needs...}}
Do not edit TASK.md. Do not fabricate the git_sha or dirty file hashes — read them for real. Once written, stop normally.`

// RequestHandoff prompts the agent to write HandoffFile before Release reads
// it. Optional capability: adapters without a live pane (tests, etc.) can
// omit it and rotate() falls back to waiting on the file appearing on its own.
type HandoffRequester interface {
	RequestHandoff(context.Context, Session) error
}

func (a CLIAdapter) RequestHandoff(ctx context.Context, s Session) error {
	return a.Client.Prompt(ctx, s.PaneID, handoffPrompt, time.Minute)
}
// Release reads the §6.1 handoff the agent wrote to HandoffFile at the
// worktree root, validates its schema and anchor against the worktree's real
// HEAD, uploads it to CAS, and only then releases herdr's claim on the pane
// via the real pane.release_agent(pane_id, source, agent) method (confirmed
// live against herdr, AUDIT.md Phase 0 — the invented "pane.release" never
// existed and could never have returned a handoff_ref regardless, since
// herdr does not write handoffs, the agent does). A missing or invalid
// handoff is refused rather than guessed at: the caller (Coordinator.rotate)
// leaves the lease intact and retries next tick, giving the agent time to
// finish writing it.
func (a CLIAdapter) Release(ctx context.Context, s Session) (string, error) {
	if a.CAS == nil {
		return "", fmt.Errorf("adapter: CAS store required to upload handoff")
	}
	path := filepath.Join(s.Worktree, HandoffFile)
	b, err := os.ReadFile(path)
	if err != nil {
		return "", fmt.Errorf("adapter: handoff not written yet (%s): %w", path, err)
	}
	h, err := continuity.Decode(b)
	if err != nil {
		return "", fmt.Errorf("adapter: invalid handoff: %w", err)
	}
	sha, err := HeadSHA(s.Worktree)
	if err != nil {
		return "", fmt.Errorf("adapter: read worktree HEAD: %w", err)
	}
	if h.Anchor.GitSHA != sha {
		return "", fmt.Errorf("adapter: handoff anchor %s does not match worktree HEAD %s", h.Anchor.GitSHA, sha)
	}
	for _, d := range h.Anchor.Dirty {
		if hex.EncodeToString(sha256sum(filepath.Join(s.Worktree, d.Path))) != d.SHA256 {
			return "", fmt.Errorf("adapter: handoff dirty file changed since it was written: %s", d.Path)
		}
	}
	// Atomically commit whatever the handoff described as dirty onto a
	// per-task scratch branch (§6.2 step 3) *before* uploading, so the
	// successor's pickup validation collapses to a single HEAD compare
	// instead of re-hashing every dirty file individually.
	if len(h.Anchor.Dirty) > 0 {
		branch := "orchestra/scratch/" + h.Meta.ID
		if err := continuity.ScratchCommit(s.Worktree, branch, "orchestra: pre-release WIP snapshot ("+h.Meta.ID+")"); err != nil {
			return "", fmt.Errorf("adapter: scratch commit: %w", err)
		}
		newSHA, err := HeadSHA(s.Worktree)
		if err != nil {
			return "", fmt.Errorf("adapter: read scratch HEAD: %w", err)
		}
		h.Anchor.GitSHA = newSHA
		h.Anchor.Branch = branch
		h.Anchor.Dirty = nil
	}
	ref, err := continuity.Save(h, a.CAS)
	if err != nil {
		return "", fmt.Errorf("adapter: upload handoff: %w", err)
	}
	if err := a.Client.Call(ctx, "pane.release_agent", map[string]any{
		"pane_id": s.PaneID,
		"source":  "herdr:" + a.Harness,
		"agent":   a.Harness,
	}, nil); err != nil {
		return "", fmt.Errorf("adapter: pane.release_agent: %w", err)
	}
	return ref, nil
}
func (a CLIAdapter) Kill(ctx context.Context, s Session) error {
	return a.Client.Call(ctx, "pane.close", map[string]any{"pane_id": s.PaneID}, nil)
}
func (a CLIAdapter) AtTurnBoundary(ctx context.Context, s Session) (bool, error) {
	status, err := a.AgentStatus(ctx, s)
	if err != nil {
		return false, err
	}
	return !IsBusy(status), nil
}
func (a CLIAdapter) PaneExited(ctx context.Context, s Session) (bool, error) {
	status, err := a.AgentStatus(ctx, s)
	if err != nil {
		return false, err
	}
	return strings.EqualFold(status, "exited") || strings.EqualFold(status, "dead"), nil
}
func (a CLIAdapter) AgentStatus(ctx context.Context, s Session) (string, error) {
	// Current herdr protocol exposes agent state through agent.get; older
	// Orchestra code used pane.status, which is not a valid protocol method.
	var r map[string]any
	if err := a.Client.Call(ctx, "agent.get", map[string]any{"target": s.PaneID}, &r); err != nil {
		return "", err
	}
	return statusFromAgentResult(r), nil
}

func (a CLIAdapter) AgentBlocker(ctx context.Context, s Session) (string, error) {
	var r struct {
		Read struct {
			Text string `json:"text"`
		} `json:"read"`
	}
	if err := a.Client.Call(ctx, "pane.read", map[string]any{"pane_id": s.PaneID, "source": "recent"}, &r); err != nil {
		return "", err
	}
	text := strings.TrimSpace(r.Read.Text)
	lines := strings.Split(text, "\n")
	for i, raw := range lines {
		line := strings.TrimSpace(strings.TrimPrefix(strings.TrimSpace(raw), "┃"))
		if !strings.EqualFold(line, "Permission required") && !strings.EqualFold(line, "Approval required") && !strings.HasPrefix(strings.ToLower(line), "waiting for") {
			continue
		}
		for _, next := range lines[i+1:] {
			command := strings.TrimSpace(strings.TrimPrefix(strings.TrimSpace(next), "┃"))
			if strings.HasPrefix(command, "$ ") {
				return strings.ToLower(line) + ": shell command `" + strings.TrimSpace(strings.TrimPrefix(command, "$ ")) + "`", nil
			}
		}
		return strings.ToLower(line), nil
	}
	return "", nil
}

func (a CLIAdapter) PaneCapture(ctx context.Context, s Session, source string) (string, error) {
	if source == "" {
		source = "recent"
	}
	var r struct {
		Read struct {
			Text string `json:"text"`
		} `json:"read"`
	}
	if err := a.Client.Call(ctx, "pane.read", map[string]any{"pane_id": s.PaneID, "source": source}, &r); err != nil {
		return "", err
	}
	return r.Read.Text, nil
}

func statusFromAgentResult(v any) string {
	if m, ok := v.(map[string]any); ok {
		for _, key := range []string{"status", "agent_status", "state"} {
			if s, ok := m[key].(string); ok && s != "" {
				return s
			}
		}
		for _, child := range m {
			if s := statusFromAgentResult(child); s != "" {
				return s
			}
		}
	}
	if a, ok := v.([]any); ok {
		for _, child := range a {
			if s := statusFromAgentResult(child); s != "" {
				return s
			}
		}
	}
	return ""
}

var _ = json.RawMessage{}

// Occupancy reads the harness's own session state — never the herdr pane id,
// which ClaudeUsage/CodexUsage/OpenCodeUsage cannot open (spec §5.2.1: "the
// whole rotation system rests on this number"). A session file that cannot
// be resolved or read is a hard error, not a silently-empty Usage{}, so
// callers (Coordinator.rotate, refreshSessionHealth) surface it instead of
// mistaking "we don't know" for "occupancy is zero".
func (a CLIAdapter) Occupancy(s Session) (float64, error) {
	if a.Usage == nil {
		return 0, fmt.Errorf("adapter: usage reader required")
	}
	path := s.SessionFile
	if path == "" {
		resolved, err := a.resolveSessionFile(s)
		if err != nil {
			return 0, fmt.Errorf("adapter: resolve session file: %w", err)
		}
		path = resolved
	}
	u, e := a.Usage(path)
	if e != nil {
		return 0, fmt.Errorf("adapter: read usage from %s: %w", path, e)
	}
	return Fraction(u, a.Window), nil
}

func (a CLIAdapter) resolveSessionFile(s Session) (string, error) {
	switch a.Harness {
	case "claude":
		return ClaudeSessionFile(s.Worktree)
	case "codex":
		_, path, err := CodexActiveUsage("")
		return path, err
	default:
		// opencode's session-file resolution needs the running session id,
		// which is only available via the SSE/status API (OpenCodeStatus),
		// not derivable from the worktree alone. Per AUDIT.md Phase 1, wiring
		// this needs verification against a live opencode instance before it
		// can drive rotation — refuse loudly rather than guess a path.
		return "", fmt.Errorf("adapter: harness %q has no session-file resolver; verify against a live session first (AUDIT.md Phase 1)", a.Harness)
	}
}

var Claude = func(c *Client, w int64, cas continuity.CAS) CLIAdapter {
	return CLIAdapter{Client: c, Harness: "claude", Window: w, Usage: ClaudeUsage, CAS: cas}
}
var Codex = func(c *Client, w int64, cas continuity.CAS) CLIAdapter {
	return CLIAdapter{Client: c, Harness: "codex", Window: w, Usage: CodexUsage, CAS: cas}
}
var OpenCode = func(c *Client, w int64, cas continuity.CAS) CLIAdapter {
	return CLIAdapter{Client: c, Harness: "opencode", Window: w, Usage: OpenCodeUsage, CAS: cas}
}