package operations

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"strings"

	"orchestra/internal/authz"
	"orchestra/internal/domain"
	"orchestra/internal/registry"
	"orchestra/internal/store"
)

// ErrNotSubmittable reports that the eligibility rule refused. The reasons are
// on the SubmissionCheck the caller passed or can recompute.
var ErrNotSubmittable = errors.New("not eligible for submission")

// ErrRemoteMismatch is a hard refusal: the remote does not hold the commit the
// plan named. Nothing is recorded, because a submission that points at the
// wrong tree is worse than no submission.
var ErrRemoteMismatch = errors.New("remote ref does not resolve to the submitted commit")

// SubmissionPlan is what a submission will do, derived from Orchestra state
// alone. It is computed before any side effect so the verify step and the
// perform step cannot disagree about what is being submitted.
type SubmissionPlan struct {
	TaskID    string
	HeadSHA   string
	Branch    string
	Remote    string
	GateRef   string
	ReviewRef string
	PacketRef string
	PRTitle   string
	PRBody    string
	// LeaseHarness and LeaseEpoch fence the resulting event when a reviewing
	// session still holds the lease.
	LeaseHarness string
	LeaseEpoch   string
	// Existing is the submission already recorded for this exact commit, if
	// any. Its presence is what makes a repeated `task pr` idempotent.
	Existing *domain.SubmissionRef
}

// Notes is the bounded, agent-supplied half of the human packet. It is
// evidence, not a completion claim: Orchestra derives everything it can from
// the contract, the decisions, the gate, the review, and git.
type Notes struct {
	BehaviouralChanges []string `json:"behavioural_changes,omitempty"`
	Deviations         []string `json:"deviations,omitempty"`
	Risks              []string `json:"risks,omitempty"`
	Hotspots           []string `json:"hotspots,omitempty"`
}

const maxNotes = 12

func (n Notes) Validate() error {
	for name, list := range map[string][]string{
		"behavioural_changes": n.BehaviouralChanges, "deviations": n.Deviations,
		"risks": n.Risks, "hotspots": n.Hotspots,
	} {
		if len(list) > maxNotes {
			return fmt.Errorf("%w: %s has %d entries, at most %d", domain.ErrInvalid, name, len(list), maxNotes)
		}
		for i, v := range list {
			if strings.TrimSpace(v) == "" {
				return fmt.Errorf("%w: %s[%d] is empty", domain.ErrInvalid, name, i)
			}
			if len(v) > 500 || strings.ContainsAny(v, "\n\r") {
				return fmt.Errorf("%w: %s[%d] must be one line of at most 500 characters", domain.ErrInvalid, name, i)
			}
		}
	}
	return nil
}

// PrepareSubmission verifies eligibility and derives the plan. It performs no
// side effect and appends no event, so calling it twice changes nothing.
func PrepareSubmission(s *store.Store, project registry.Project, taskID, headSHA string, gate domain.GateResult, notes Notes) (SubmissionPlan, error) {
	if err := notes.Validate(); err != nil {
		return SubmissionPlan{}, err
	}
	t, ok := s.Task(taskID)
	if !ok {
		return SubmissionPlan{}, domain.ErrNotFound
	}
	check := domain.CheckSubmission(t, headSHA, gate)
	reasons := append(check.Reasons, t.RequirePhaseArtifacts(project.Phases())...)
	if len(reasons) > 0 {
		// An existing submission for this exact commit is not a failure. It is
		// the same submission, and returning it is what makes a retry safe.
		if t.Submitted(headSHA) && onlyStateReasons(reasons) {
			return planFor(s, t, project, headSHA, gate, notes)
		}
		return SubmissionPlan{}, fmt.Errorf("%w: %s", ErrNotSubmittable, strings.Join(reasons, "; "))
	}
	return planFor(s, t, project, headSHA, gate, notes)
}

// onlyStateReasons reports whether every refusal is a consequence of the task
// already being submitted, rather than a real defect in eligibility.
func onlyStateReasons(reasons []string) bool {
	for _, r := range reasons {
		if !strings.Contains(r, "work phase is") && !strings.Contains(r, "already") {
			return false
		}
	}
	return true
}

func planFor(s *store.Store, t domain.Task, project registry.Project, headSHA string, gate domain.GateResult, notes Notes) (SubmissionPlan, error) {
	gateRef, err := s.PutArtifact(gateEvidence(gate))
	if err != nil {
		return SubmissionPlan{}, err
	}
	packet, err := SubmissionPacket(s, t, headSHA, gate, notes)
	if err != nil {
		return SubmissionPlan{}, err
	}
	packetRef, err := s.PutArtifact([]byte(packet))
	if err != nil {
		return SubmissionPlan{}, err
	}
	plan := SubmissionPlan{
		TaskID: t.ID, HeadSHA: headSHA, Branch: "orchestra/" + t.ID,
		// The remote name is a worker-side deployment detail; submission names
		// the conventional default and the executor may override it.
		Remote:  "origin",
		GateRef: gateRef, PacketRef: packetRef,
		PRTitle: prTitle(t), PRBody: packet, Existing: t.Submission,
	}
	if t.Review != nil {
		plan.ReviewRef = t.Review.ArtifactRef
	}
	if t.Lease != nil {
		plan.LeaseHarness, plan.LeaseEpoch = t.Lease.HarnessID, t.Lease.Epoch
	}
	return plan, nil
}

func prTitle(t domain.Task) string {
	title := oneLine(firstNonEmpty(t.Title, t.Description, "Orchestra task "+t.ID))
	if len(title) > 120 {
		title = title[:120]
	}
	return title
}

func gateEvidence(g domain.GateResult) []byte {
	b, _ := json.Marshal(g)
	return b
}

// Publisher is the side-effecting half. It is an interface so submission can
// be tested without a forge, and so the git and forge steps stay separable.
type Publisher interface {
	// Push publishes exactly the named commit and returns what the remote
	// resolves the branch to afterwards.
	Push(ctx context.Context, remote, branch, sha string) (string, error)
	// EnsurePR creates the pull request or updates the existing one for this
	// branch. It must never create a second pull request for the same branch.
	EnsurePR(ctx context.Context, plan SubmissionPlan) (domain.ExternalRef, error)
}

// HeadResolver reads the current commit, so execution can re-check it
// immediately before pushing and again before recording success.
type HeadResolver func(ctx context.Context) (string, error)

// ExecuteSubmission performs the plan and records it.
//
// The commit is re-read immediately before the push and again before the event
// is appended, so a tree that moved after eligibility was computed cannot be
// submitted under the old verdict. A transport failure leaves the task
// review-ready and retryable rather than in a fake terminal state.
func ExecuteSubmission(ctx context.Context, s *store.Store, plan SubmissionPlan, pub Publisher, head HeadResolver) (domain.Event, error) {
	if head != nil {
		current, err := head(ctx)
		if err != nil {
			return domain.Event{}, fmt.Errorf("re-read head before push: %w", err)
		}
		if current != plan.HeadSHA {
			return domain.Event{}, fmt.Errorf("%w: head moved from %s to %s before push", ErrNotSubmittable, plan.HeadSHA, current)
		}
	}
	remoteSHA, err := pub.Push(ctx, plan.Remote, plan.Branch, plan.HeadSHA)
	if err != nil {
		return domain.Event{}, fmt.Errorf("push %s: %w", plan.Branch, err)
	}
	if remoteSHA != plan.HeadSHA {
		return domain.Event{}, fmt.Errorf("%w: %s holds %s, expected %s", ErrRemoteMismatch, plan.Branch, remoteSHA, plan.HeadSHA)
	}
	pr, err := pub.EnsurePR(ctx, plan)
	if err != nil {
		// The push stands. A retry re-verifies the pushed commit and continues
		// from here rather than starting over.
		return domain.Event{}, fmt.Errorf("pull request for %s: %w", plan.Branch, err)
	}
	if head != nil {
		current, err := head(ctx)
		if err != nil {
			return domain.Event{}, fmt.Errorf("re-read head before recording: %w", err)
		}
		if current != plan.HeadSHA {
			return domain.Event{}, fmt.Errorf("%w: head moved to %s while submitting", ErrNotSubmittable, current)
		}
	}
	t, ok := s.Task(plan.TaskID)
	if !ok {
		return domain.Event{}, domain.ErrNotFound
	}
	if t.Submitted(plan.HeadSHA) {
		// Already recorded for this commit. The push and the pull request were
		// both idempotent, so this is the same submission, not a second one.
		return domain.Event{}, nil
	}
	payload := map[string]any{
		"result_sha": plan.HeadSHA,
		"remote_ref": plan.Remote + "/" + plan.Branch,
		"pr":         pr,
		"gate_ref":   plan.GateRef,
		"review_ref": plan.ReviewRef,
		"packet_ref": plan.PacketRef,
	}
	if plan.LeaseEpoch != "" {
		payload["harness_id"], payload["lease_epoch"] = plan.LeaseHarness, plan.LeaseEpoch
	}
	b, err := json.Marshal(payload)
	if err != nil {
		return domain.Event{}, err
	}
	e := domain.Event{ID: domain.NewID(), Type: domain.EventTaskSubmitted, TaskID: plan.TaskID, Version: t.Version + 1, Payload: b, Surface: string(authz.System)}
	return e, s.Append(e)
}

// SubmissionPacket is the human's single review packet. Orchestra derives
// everything it can; the agent's contribution is bounded and labelled as its
// own account rather than as verified fact.
func SubmissionPacket(s *store.Store, t domain.Task, headSHA string, gate domain.GateResult, notes Notes) (string, error) {
	intent, err := s.EffectiveIntent(t.ID)
	if err != nil {
		return "", err
	}
	var b strings.Builder
	fmt.Fprintf(&b, "## Goal\n\n%s\n", oneLine(firstNonEmpty(t.Title, t.Description, "not stated")))
	if t.Description != "" && t.Title != "" {
		fmt.Fprintf(&b, "\n%s\n", oneLine(t.Description))
	}

	b.WriteString("\n## Acceptance\n\n")
	if len(t.Acceptance) == 0 {
		b.WriteString("- not stated in the task contract\n")
	}
	for _, a := range t.Acceptance {
		fmt.Fprintf(&b, "- %s\n", oneLine(a))
	}

	if len(intent.Decisions) > 0 {
		b.WriteString("\n## Human decisions\n\n")
		for _, d := range intent.Decisions {
			fmt.Fprintf(&b, "- %s (%s): %s\n", d.Kind, d.Subject, oneLine(d.Value))
		}
	}

	b.WriteString("\n## Verification\n\n")
	if gate.Command != "" {
		fmt.Fprintf(&b, "- `%s` exited %d\n", oneLine(gate.Command), gate.ExitCode)
	}
	fmt.Fprintf(&b, "- commit: %s\n", headSHA)
	if t.Review != nil {
		verdict := "pass"
		if t.Review.Blocking > 0 {
			verdict = fmt.Sprintf("%d unresolved blocking findings", t.Review.Blocking)
		}
		fmt.Fprintf(&b, "- independent review of %s: %s\n", t.Review.ResultSHA, verdict)
		if r, err := TaskReview(s, t); err == nil && r != nil {
			minor := len(r.Findings) - len(r.Blocking())
			if minor > 0 {
				fmt.Fprintf(&b, "- minor findings, not fixed: %d\n", minor)
			}
		}
	}
	if t.PlanRef != "" {
		fmt.Fprintf(&b, "- accepted plan: %s\n", t.PlanRef)
	}

	writeNotes(&b, "Behavioural changes", notes.BehaviouralChanges, "none reported")
	writeNotes(&b, "Deviations from plan", notes.Deviations, "none reported")
	writeNotes(&b, "Remaining risks", notes.Risks, "none reported")
	writeNotes(&b, "Review hotspots", notes.Hotspots, "none reported")

	if r, err := TaskReview(s, t); err == nil && r != nil && len(r.Findings) > 0 {
		b.WriteString("\n## Reviewer findings\n\n")
		for _, f := range r.Findings {
			where := oneLine(f.File)
			if f.Line > 0 {
				where = fmt.Sprintf("%s:%d", where, f.Line)
			}
			fmt.Fprintf(&b, "- %s: `%s` %s\n", f.Severity, where, oneLine(f.Claim))
		}
	}
	if found := DeferredFindings(s, t.ID); len(found) > 0 {
		b.WriteString("\n## Deferred, not done here\n\n")
		for _, f := range found {
			fmt.Fprintf(&b, "- %s (%s)\n", oneLine(f.Summary), oneLine(f.Why))
		}
	}
	b.WriteString("\nThe sections above are derived from Orchestra state. The reported\n")
	b.WriteString("changes, deviations, risks, and hotspots are the implementing agent's\n")
	b.WriteString("own account and are not verified.\n")
	return b.String(), nil
}

func writeNotes(b *strings.Builder, heading string, items []string, empty string) {
	fmt.Fprintf(b, "\n## %s\n\n", heading)
	if len(items) == 0 {
		fmt.Fprintf(b, "- %s\n", empty)
		return
	}
	for _, item := range items {
		fmt.Fprintf(b, "- %s\n", oneLine(item))
	}
}