package runner

import (
	"context"
	"fmt"
	"time"

	"gitea.maximumdirect.net/eric/audita/internal/core/config"
	"gitea.maximumdirect.net/eric/audita/internal/core/schema"
	"gitea.maximumdirect.net/eric/audita/internal/framework/contracts"
	"gitea.maximumdirect.net/eric/audita/internal/framework/proposals"
)

const (
	ModuleStatusSuccess = "success"
	ModuleStatusFailed  = "failed"
)

// ModuleFactory resolves one module instance for one run spec.
type ModuleFactory interface {
	ModuleForSpec(spec contracts.ModuleRunSpec) (contracts.TranscriptModule, error)
}

// Runner executes module instances sequentially against a working transcript.
type Runner struct {
	factory ModuleFactory
}

// ModuleResult captures deterministic per-module execution output.
type ModuleResult struct {
	ModuleKey         string                      `json:"module_key"`
	ModuleInstance    string                      `json:"module_instance"`
	ReplacementPolicy proposals.ReplacementPolicy `json:"replacement_policy"`
	Status            string                      `json:"status"`
	ProposalCount     int                         `json:"proposal_count"`
	AppliedChanges    []proposals.AppliedChange   `json:"applied_changes,omitempty"`
	SkippedChanges    []proposals.SkippedChange   `json:"skipped_changes,omitempty"`
	ErrorMessage      string                      `json:"error_message,omitempty"`
	StartedAt         time.Time                   `json:"started_at"`
	CompletedAt       time.Time                   `json:"completed_at"`
}

// RunInput is the deterministic runner input.
type RunInput struct {
	Config      *config.Config
	Transcript  *schema.Transcript
	Glossary    *schema.Glossary
	ModuleSpecs []contracts.ModuleRunSpec
}

// RunOutput is the deterministic runner output.
type RunOutput struct {
	FinalTranscript *schema.Transcript `json:"-"`
	ModuleResults   []ModuleResult     `json:"module_results"`
}

func New(factory ModuleFactory) *Runner {
	return &Runner{factory: factory}
}

func (r *Runner) Run(ctx context.Context, input RunInput) (RunOutput, error) {
	if r == nil || r.factory == nil {
		return RunOutput{}, fmt.Errorf("runner module factory is required")
	}

	working := cloneTranscript(input.Transcript)
	results := make([]ModuleResult, 0, len(input.ModuleSpecs))

	for _, spec := range input.ModuleSpecs {
		startedAt := time.Now().UTC()
		module, err := r.factory.ModuleForSpec(spec)
		if err != nil {
			failed := ModuleResult{
				ModuleKey:      spec.ModuleKey,
				ModuleInstance: spec.InstanceName,
				Status:         ModuleStatusFailed,
				ErrorMessage:   err.Error(),
				StartedAt:      startedAt,
				CompletedAt:    time.Now().UTC(),
			}
			results = append(results, failed)
			return RunOutput{FinalTranscript: working, ModuleResults: results}, fmt.Errorf("module %q setup failed: %w", spec.InstanceName, err)
		}

		policy := module.ReplacementPolicy()
		proposed, err := module.Propose(ctx, contracts.ProposalRequest{
			ExecutionContext: contracts.ExecutionContext{
				Config:            input.Config,
				WorkingTranscript: working,
				Glossary:          input.Glossary,
			},
			RunSpec: contracts.ModuleRunSpec{
				ModuleKey:         spec.ModuleKey,
				InstanceName:      spec.InstanceName,
				ReplacementPolicy: policy,
			},
		})
		if err != nil {
			failed := ModuleResult{
				ModuleKey:         spec.ModuleKey,
				ModuleInstance:    spec.InstanceName,
				ReplacementPolicy: policy,
				Status:            ModuleStatusFailed,
				ErrorMessage:      err.Error(),
				StartedAt:         startedAt,
				CompletedAt:       time.Now().UTC(),
			}
			results = append(results, failed)
			return RunOutput{FinalTranscript: working, ModuleResults: results}, fmt.Errorf("module %q failed: %w", spec.InstanceName, err)
		}

		enriched := make([]proposals.EnrichedCorrectionProposal, 0, len(proposed))
		for i, p := range proposed {
			enriched = append(enriched, proposals.EnrichedCorrectionProposal{
				CorrectionProposal: p,
				ProposalMetadata: proposals.ProposalMetadata{
					ProposalIndex:  i,
					ModuleKey:      spec.ModuleKey,
					ModuleInstance: spec.InstanceName,
				},
			})
		}

		applyResult := proposals.ApplyProposals(working, enriched, policy)
		working = applyResult.Transcript

		results = append(results, ModuleResult{
			ModuleKey:         spec.ModuleKey,
			ModuleInstance:    spec.InstanceName,
			ReplacementPolicy: policy,
			Status:            ModuleStatusSuccess,
			ProposalCount:     len(enriched),
			AppliedChanges:    applyResult.Applied,
			SkippedChanges:    applyResult.Skipped,
			StartedAt:         startedAt,
			CompletedAt:       time.Now().UTC(),
		})
	}

	return RunOutput{FinalTranscript: working, ModuleResults: results}, nil
}

func cloneTranscript(t *schema.Transcript) *schema.Transcript {
	if t == nil {
		return &schema.Transcript{}
	}
	segments := make([]schema.Segment, len(t.Segments))
	for i, s := range t.Segments {
		var categories []string
		if s.Categories != nil {
			categories = append([]string(nil), s.Categories...)
		}
		segments[i] = schema.Segment{
			ID:         s.ID,
			Speaker:    s.Speaker,
			Start:      s.Start,
			End:        s.End,
			Text:       s.Text,
			Categories: categories,
		}
	}
	return &schema.Transcript{Segments: segments}
}