package domain

import (
	"fmt"
	"strings"
)

// EventPlanMismatchRecorded records that implementation found the accepted
// plan contradicted by the code.
//
// It is deliberately not the same thing as the plan being superseded. A
// mismatch is an observation; a plan stops being accepted only when a
// replacement is sealed. Conflating the two would let an abandoned replan
// erase the plan the task is still working from.
const EventPlanMismatchRecorded = "PlanMismatchRecorded"

// BlockReasonPlanMismatch is a deliberate stop, not a fault: the implementer
// found a contradiction it may not resolve alone, and the human decides
// whether the plan still holds.
const BlockReasonPlanMismatch BlockReason = "plan_mismatch"

// PlanMismatchAction is what the implementer believes should happen. It is
// advisory: Orchestra owns the reopen, and a request that asks for a replan
// may still get a human decision instead.
type PlanMismatchAction string

const (
	// PlanMismatchReplan: the goal still holds, the route does not.
	PlanMismatchReplan PlanMismatchAction = "replan"
	// PlanMismatchResearch: the plan rests on something the repository does
	// not actually establish, so planning again would repeat the mistake.
	PlanMismatchResearch PlanMismatchAction = "research"
	// PlanMismatchHumanDecision: the contradiction is about intent, which no
	// amount of reading the repository settles.
	PlanMismatchHumanDecision PlanMismatchAction = "human_decision"
)

func (a PlanMismatchAction) Valid() bool {
	switch a {
	case PlanMismatchReplan, PlanMismatchResearch, PlanMismatchHumanDecision:
		return true
	}
	return false
}

// PlanMismatch is the implementer's bounded report that the plan does not
// match the code.
//
// It carries an observation and nothing else. A request may not propose a
// replacement plan: writing the next plan is the planning phase's work, and an
// implementer that could supply one would be planning from inside the phase
// that was supposed to execute a plan.
type PlanMismatch struct {
	// PlanRef, PhaseID and AtSHA bind the report to what the implementer was
	// actually looking at. All three are checked before anything is recorded,
	// so a request written against an older plan or an older tree is refused
	// rather than replayed against the current one.
	PlanRef string `json:"plan_ref"`
	PhaseID string `json:"phase_id"`
	AtSHA   string `json:"at_sha"`
	// Observed is what the code does.
	Observed string `json:"observed"`
	// Contradicts is the part of the plan that says otherwise.
	Contradicts string `json:"contradicts"`
	// Evidence points at what can be checked: paths, symbols, commands.
	Evidence        []string           `json:"evidence,omitempty"`
	RequestedAction PlanMismatchAction `json:"requested_action"`
}

const (
	maxMismatchField    = 1000
	maxMismatchEvidence = 8
)

func (m PlanMismatch) Validate() error {
	if strings.TrimSpace(m.PlanRef) == "" {
		return fmt.Errorf("%w: plan_ref required", ErrInvalid)
	}
	if strings.TrimSpace(m.PhaseID) == "" {
		return fmt.Errorf("%w: phase_id required", ErrInvalid)
	}
	if len(m.AtSHA) != 40 {
		return fmt.Errorf("%w: at_sha must be a full commit sha", ErrInvalid)
	}
	if !m.RequestedAction.Valid() {
		return fmt.Errorf("%w: requested_action %q is not replan, research, or human_decision", ErrInvalid, m.RequestedAction)
	}
	for name, v := range map[string]string{"observed": m.Observed, "contradicts": m.Contradicts} {
		if err := mismatchField(name, v); err != nil {
			return err
		}
	}
	if len(m.Evidence) > maxMismatchEvidence {
		return fmt.Errorf("%w: %d evidence entries exceeds the %d bound", ErrInvalid, len(m.Evidence), maxMismatchEvidence)
	}
	for i, v := range m.Evidence {
		if err := mismatchField(fmt.Sprintf("evidence[%d]", i), v); err != nil {
			return err
		}
	}
	return nil
}

func mismatchField(name, v string) error {
	s := strings.TrimSpace(v)
	if s == "" {
		return fmt.Errorf("%w: %s is required", ErrInvalid, name)
	}
	if len(s) > maxMismatchField {
		return fmt.Errorf("%w: %s is %d characters, at most %d", ErrInvalid, name, len(s), maxMismatchField)
	}
	return nil
}

func ValidatePlanMismatchRecorded(p map[string]any) error {
	m := PlanMismatch{}
	m.PlanRef, _ = p["plan_ref"].(string)
	m.PhaseID, _ = p["phase_id"].(string)
	m.AtSHA, _ = p["at_sha"].(string)
	m.Observed, _ = p["observed"].(string)
	m.Contradicts, _ = p["contradicts"].(string)
	action, _ := p["requested_action"].(string)
	m.RequestedAction = PlanMismatchAction(action)
	if raw, ok := p["evidence"].([]any); ok {
		for _, v := range raw {
			s, _ := v.(string)
			m.Evidence = append(m.Evidence, s)
		}
	}
	return m.Validate()
}

// reopenPhases is the set of backward moves Orchestra may make, and no agent
// may ask for. They exist because a contradiction found during implementation
// is real information, and refusing to act on it would leave the task
// implementing against a plan everyone knows is wrong.
//
// The edge belongs to Orchestra rather than the phase graph so that
// phase-request.json still refuses a backward move: an agent asks by reporting
// a mismatch, and Orchestra decides.
var reopenPhases = map[WorkPhase][]WorkPhase{
	WorkPhaseImplement: {WorkPhasePlan, WorkPhaseResearch},
}

// CanReopenPhase reports whether Orchestra may reopen this phase. It is
// separate from CanTransitionPhase on purpose: every caller that validates an
// agent's request uses that one, so a reopen cannot be reached by asking.
func CanReopenPhase(from, to WorkPhase) bool {
	for _, allowed := range reopenPhases[from] {
		if allowed == to {
			return true
		}
	}
	return false
}