// Package registry contains the static project, machine, and herdr topology.
package registry

import (
	"encoding/json"
	"errors"
	"fmt"
	"net"
	"os"
	"sort"
	"strings"
	"time"

	"orchestra/internal/domain"
)

var (
	ErrUnknownProject = errors.New("unknown project")
	ErrUnknownMachine = errors.New("unknown machine")
	ErrNoAffinity     = errors.New("project has no machine affinity")
)

type Project struct {
	ID              string   `json:"id"`
	MachineAffinity []string `json:"machine_affinity"`
	// Repo and WorktreeRoot let each project resolve its own git checkout
	// (spec §2.2 — a project is first-class; nothing about the model implies
	// a single shared repo across all projects). Both optional: a project
	// that omits them falls back to whatever global default the deployment
	// wires (single-repo deployments keep working unchanged).
	Repo         string `json:"repo,omitempty"`
	WorktreeRoot string `json:"worktree_root,omitempty"`
	QualityGate  string `json:"quality_gate,omitempty"`
	// SafeOperations is an audited, deliberately small allow-list for work
	// inside this project's task worktree. It documents what workers may
	// perform without an operator grant; network, secrets, destructive Git,
	// and paths outside the worktree are never represented here.
	SafeOperations []string `json:"safe_operations,omitempty"`
	// WorkPhases is the phase path this project's tasks follow. Empty means
	// the default path. A phase not listed here is skipped, which is how a
	// trivial project runs frame, implement, review with no research or plan.
	WorkPhases []domain.WorkPhase `json:"work_phases,omitempty"`
	// TrajectoryGate names the phase transitions the human must confirm
	// before work continues, keyed "<from>_to_<to>" with value "required".
	// Anything else, including an absent key, is automatic. Explicit policy
	// beats a complexity classifier until there is evidence one is needed.
	TrajectoryGate map[string]string `json:"trajectory_gate,omitempty"`
	// HumanDecisions bounds how often one task may stop to ask. Zero uses the
	// default.
	HumanDecisions struct {
		MaxRequestsPerTask int `json:"max_requests_per_task,omitempty"`
	} `json:"human_decisions,omitempty"`
}

// MaxDecisionRequests is the per-task question budget.
func (p Project) MaxDecisionRequests() int {
	if p.HumanDecisions.MaxRequestsPerTask > 0 {
		return p.HumanDecisions.MaxRequestsPerTask
	}
	return defaultMaxDecisionRequests
}

// GateRequired reports whether this transition needs human confirmation.
func (p Project) GateRequired(from, to domain.WorkPhase) bool {
	if from == "" {
		from = domain.WorkPhaseFrame
	}
	return strings.EqualFold(p.TrajectoryGate[string(from)+"_to_"+string(to)], "required")
}

// defaultMaxDecisionRequests mirrors operations.DefaultMaxDecisionRequests,
// duplicated to keep registry free of a dependency on operations.
const defaultMaxDecisionRequests = 6

// DefaultWorkPhases is the path a project takes when it declares none.
var DefaultWorkPhases = []domain.WorkPhase{domain.WorkPhaseFrame, domain.WorkPhaseResearch, domain.WorkPhasePlan, domain.WorkPhaseImplement, domain.WorkPhaseReview}

// Phases returns the declared path, or the default.
func (p Project) Phases() []domain.WorkPhase {
	if len(p.WorkPhases) == 0 {
		return DefaultWorkPhases
	}
	return p.WorkPhases
}

// NextPhase returns the phase that follows current on this project's path,
// skipping any phase the project does not declare. It reports false at the
// end of the path. The result is always a legal transition, so a project
// cannot declare a path that moves backwards.
func (p Project) NextPhase(current domain.WorkPhase) (domain.WorkPhase, bool) {
	if current == "" {
		current = domain.WorkPhaseFrame
	}
	phases := p.Phases()
	// Review's only legal move is back to implement, the one backwards edge
	// in the model. Review passing is not a phase change: it is completion,
	// which belongs to the task lifecycle.
	if current == domain.WorkPhaseReview {
		for _, phase := range phases {
			if phase == domain.WorkPhaseImplement {
				return domain.WorkPhaseImplement, true
			}
		}
		return "", false
	}
	for i, phase := range phases {
		if phase != current {
			continue
		}
		for _, candidate := range phases[i+1:] {
			if domain.CanTransitionPhase(current, candidate) {
				return candidate, true
			}
		}
		return "", false
	}
	return "", false
}

type Machine struct {
	ID      string `json:"id"`
	Address string `json:"address"`
}
type Herdr struct {
	ID        string `json:"id"`
	MachineID string `json:"machine_id"`
	// Backend selects the machine-local pane implementation. The empty value
	// preserves the existing herdr default. tmux is currently Claude-only.
	Backend      string   `json:"backend,omitempty"`
	Address      string   `json:"address,omitempty"`
	Harness      string   `json:"harness,omitempty"`
	Protocol     string   `json:"protocol,omitempty"`
	Capabilities []string `json:"capabilities"`
	Concurrency  int      `json:"concurrency"`
	// QuotaLimit is deprecated in favor of QuotaLimit5h/QuotaLimitWeekly; if
	// set and QuotaLimit5h is not, it is treated as the weekly limit only
	// (its historical meaning), to avoid silently inventing a 5h cap for
	// existing configuration.
	QuotaLimit       float64 `json:"quota_limit,omitempty"`
	QuotaLimit5h     float64 `json:"quota_limit_5h,omitempty"`
	QuotaLimitWeekly float64 `json:"quota_limit_weekly,omitempty"`
}

const defaultHerdrPort = "9245"

type Config struct {
	Projects []Project `json:"projects"`
	Machines []Machine `json:"machines"`
	Herdrs   []Herdr   `json:"herdrs"`
}
type Registry struct {
	projects map[string]Project
	machines map[string]Machine
	herdrs   map[string]Herdr
}

func Load(path string) (Registry, error) {
	b, err := os.ReadFile(path)
	if err != nil {
		return Registry{}, err
	}
	var c Config
	if err = json.Unmarshal(stripJSONComments(b), &c); err != nil {
		return Registry{}, fmt.Errorf("registry config: %w", err)
	}
	return New(c)
}

// stripJSONComments removes // line comments and /* */ block comments from
// JSONC input, leaving valid JSON. Comment markers inside string literals
// (respecting backslash escapes) are left untouched. This lets deployments
// annotate config.json in place instead of keeping a separate undocumented
// copy (see deploy/config.example.jsonc).
func stripJSONComments(b []byte) []byte {
	out := make([]byte, 0, len(b))
	inString, escaped, inLineComment, inBlockComment := false, false, false, false
	for i := 0; i < len(b); i++ {
		c := b[i]
		switch {
		case inLineComment:
			if c == '\n' {
				inLineComment = false
				out = append(out, c)
			}
		case inBlockComment:
			if c == '*' && i+1 < len(b) && b[i+1] == '/' {
				inBlockComment = false
				i++
			}
		case inString:
			out = append(out, c)
			if escaped {
				escaped = false
			} else if c == '\\' {
				escaped = true
			} else if c == '"' {
				inString = false
			}
		case c == '"':
			inString = true
			out = append(out, c)
		case c == '/' && i+1 < len(b) && b[i+1] == '/':
			inLineComment = true
			i++
		case c == '/' && i+1 < len(b) && b[i+1] == '*':
			inBlockComment = true
			i++
		default:
			out = append(out, c)
		}
	}
	return out
}

func New(c Config) (Registry, error) {
	r := Registry{map[string]Project{}, map[string]Machine{}, map[string]Herdr{}}
	for _, p := range c.Projects {
		if err := putID(r.projects, p.ID, "project"); err != nil {
			return Registry{}, err
		}
		if len(p.MachineAffinity) == 0 {
			return Registry{}, fmt.Errorf("project %q: %w", p.ID, ErrNoAffinity)
		}
		for _, op := range p.SafeOperations {
			switch op {
			case "read", "edit", "test", "git":
			default:
				return Registry{}, fmt.Errorf("project %q: unsafe operation %q is not policy-configurable", p.ID, op)
			}
		}
		r.projects[p.ID] = p
	}
	for _, m := range c.Machines {
		if err := putID(r.machines, m.ID, "machine"); err != nil {
			return Registry{}, err
		}
		if strings.TrimSpace(m.Address) == "" {
			return Registry{}, fmt.Errorf("machine %q: address required", m.ID)
		}
		r.machines[m.ID] = m
	}
	for _, h := range c.Herdrs {
		if err := putID(r.herdrs, h.ID, "herdr"); err != nil {
			return Registry{}, err
		}
		if _, ok := r.machines[h.MachineID]; !ok {
			return Registry{}, fmt.Errorf("herdr %q: %w %q", h.ID, ErrUnknownMachine, h.MachineID)
		}
		if h.Concurrency < 0 {
			return Registry{}, fmt.Errorf("herdr %q: negative concurrency", h.ID)
		}
		switch h.Backend {
		case "", "herdr":
		case "tmux":
			if h.Harness != "claude" {
				return Registry{}, fmt.Errorf("herdr %q: tmux backend currently supports only claude, got %q", h.ID, h.Harness)
			}
		default:
			return Registry{}, fmt.Errorf("herdr %q: unsupported backend %q", h.ID, h.Backend)
		}
		r.herdrs[h.ID] = h
	}
	for _, p := range r.projects {
		for _, m := range p.MachineAffinity {
			if _, ok := r.machines[m]; !ok {
				return Registry{}, fmt.Errorf("project %q: %w %q", p.ID, ErrUnknownMachine, m)
			}
		}
	}
	return r, nil
}
func putID[T any](m map[string]T, id, kind string) error {
	if strings.TrimSpace(id) == "" {
		return fmt.Errorf("%s id required", kind)
	}
	if _, ok := m[id]; ok {
		return fmt.Errorf("duplicate %s %q", kind, id)
	}
	return nil
}
func (r Registry) Project(id string) (Project, bool) { p, ok := r.projects[id]; return p, ok }
func (r Registry) Machine(id string) (Machine, bool) { m, ok := r.machines[id]; return m, ok }
func (r Registry) Herdr(id string) (Herdr, bool)     { h, ok := r.herdrs[id]; return h, ok }
func (r Registry) Machines() []Machine {
	out := make([]Machine, 0, len(r.machines))
	for _, m := range r.machines {
		out = append(out, m)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].ID < out[j].ID })
	return out
}
func (r Registry) Herdrs() []Herdr {
	out := make([]Herdr, 0, len(r.herdrs))
	for _, h := range r.herdrs {
		out = append(out, h)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].ID < out[j].ID })
	return out
}
func (r Registry) Projects() []Project { return projects(r.projects) }
func projects(m map[string]Project) []Project {
	out := make([]Project, 0, len(m))
	for _, v := range m {
		out = append(out, v)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].ID < out[j].ID })
	return out
}

type Reachability interface {
	Reachable(address string, timeout time.Duration) bool
}
type TCPReachability struct{}

func (TCPReachability) Reachable(address string, timeout time.Duration) bool {
	c, err := net.DialTimeout("tcp", address, timeout)
	if err != nil {
		return false
	}
	_ = c.Close()
	return true
}
func (r Registry) Candidates(project string, check Reachability, timeout time.Duration) ([]Herdr, error) {
	return r.candidates(project, func(h Herdr) bool {
		address := r.Endpoint(h)
		return check == nil || check.Reachable(address, timeout)
	})
}

// CandidatesWithHealth filters candidates using a health snapshot gathered by
// the router. Keeping probe execution outside this method lets a scheduling
// pass probe each herdr once, in parallel, instead of once per queued task.
func (r Registry) CandidatesWithHealth(project string, healthy map[string]bool) ([]Herdr, error) {
	return r.candidates(project, func(h Herdr) bool { return healthy[h.ID] })
}

func (r Registry) candidates(project string, include func(Herdr) bool) ([]Herdr, error) {
	p, ok := r.projects[project]
	if !ok {
		return nil, ErrUnknownProject
	}
	allowed := map[string]bool{}
	for _, m := range p.MachineAffinity {
		allowed[m] = true
	}
	out := []Herdr{}
	for _, h := range r.herdrs {
		if !allowed[h.MachineID] || !include(h) {
			continue
		}
		out = append(out, h)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].ID < out[j].ID })
	return out, nil
}

// Endpoint resolves the backend-specific health key. Worker-owned tmux
// backends use an identity-only pseudo endpoint so bypassing their legacy TCP
// probe cannot accidentally bypass another local herdr sharing port 9245.
func (r Registry) Endpoint(h Herdr) string {
	if h.Backend == "tmux" {
		return "tmux:" + h.ID
	}
	if h.Address != "" {
		return h.Address
	}
	address := r.machines[h.MachineID].Address
	if host, _, err := net.SplitHostPort(address); err == nil {
		return net.JoinHostPort(host, defaultHerdrPort)
	}
	return address
}