package trim

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"sort"

	"gitea.maximumdirect.net/eric/seriatim/internal/config"
	"gitea.maximumdirect.net/eric/seriatim/internal/jsonfile"
	"gitea.maximumdirect.net/eric/seriatim/internal/report"
)

type auditReport struct {
	Operation               string      `json:"operation"`
	InputFile               string      `json:"input_file"`
	OutputFile              string      `json:"output_file"`
	InputSchema             string      `json:"input_schema"`
	OutputSchema            string      `json:"output_schema"`
	Mode                    string      `json:"mode"`
	Selector                string      `json:"selector"`
	SelectedIDs             []int       `json:"selected_ids"`
	AllowEmpty              bool        `json:"allow_empty"`
	InputSegmentCount       int         `json:"input_segment_count"`
	RetainedSegmentCount    int         `json:"retained_segment_count"`
	RemovedSegmentCount     int         `json:"removed_segment_count"`
	RemovedInputIDs         []int       `json:"removed_input_ids"`
	OldToNewIDMapping       []idMapping `json:"old_to_new_id_mapping"`
	OverlapGroupsRecomputed bool        `json:"overlap_groups_recomputed"`
}

type idMapping struct {
	OldID int `json:"old_id"`
	NewID int `json:"new_id"`
}

// Run executes artifact-level trim orchestration.
func Run(ctx context.Context, cfg config.TrimConfig) error {
	if err := ctx.Err(); err != nil {
		return err
	}

	selector, err := ParseSelector(cfg.Selector)
	if err != nil {
		return fmt.Errorf("invalid selector %q: %w", cfg.Selector, err)
	}

	data, err := os.ReadFile(cfg.InputFile)
	if err != nil {
		return fmt.Errorf("read --input-file %q: %w", cfg.InputFile, err)
	}

	artifact, err := ParseArtifactJSON(data)
	if err != nil {
		return fmt.Errorf("--input-file %q: %w", cfg.InputFile, err)
	}
	inputSegmentCount := artifact.SegmentCount()
	inputSchema := artifact.Schema

	mode := ModeKeep
	if cfg.Mode == "remove" {
		mode = ModeRemove
	}

	trimmed, err := ApplyArtifact(artifact, Options{
		Mode:       mode,
		Selector:   selector,
		AllowEmpty: cfg.AllowEmpty,
	})
	if err != nil {
		return err
	}

	outputSchema := artifact.Schema
	if cfg.OutputSchema != "" {
		outputSchema = cfg.OutputSchema
	}

	outputArtifact, err := ConvertArtifact(trimmed.Artifact, outputSchema)
	if err != nil {
		return err
	}

	if err := ValidateArtifact(outputArtifact); err != nil {
		return fmt.Errorf("validate trimmed output: %w", err)
	}

	if err := jsonfile.Write(cfg.OutputFile, outputArtifact.Value()); err != nil {
		return err
	}

	if cfg.ReportFile == "" {
		return nil
	}

	audit := auditReport{
		Operation:               "trim",
		InputFile:               cfg.InputFile,
		OutputFile:              cfg.OutputFile,
		InputSchema:             inputSchema,
		OutputSchema:            outputArtifact.Schema,
		Mode:                    cfg.Mode,
		Selector:                cfg.Selector,
		SelectedIDs:             selector.IDs(),
		AllowEmpty:              cfg.AllowEmpty,
		InputSegmentCount:       inputSegmentCount,
		RetainedSegmentCount:    len(trimmed.OldToNewID),
		RemovedSegmentCount:     len(trimmed.RemovedIDs),
		RemovedInputIDs:         append([]int(nil), trimmed.RemovedIDs...),
		OldToNewIDMapping:       orderedIDMapping(trimmed.OldToNewID),
		OverlapGroupsRecomputed: trimmed.OverlapGroupsRecomputed,
	}
	auditJSON, err := json.Marshal(audit)
	if err != nil {
		return fmt.Errorf("marshal trim audit report: %w", err)
	}

	rpt := report.Report{
		Metadata: report.Metadata{
			Application:   outputArtifact.Application(),
			Version:       outputArtifact.Version(),
			InputReader:   "trim-artifact",
			InputFiles:    []string{cfg.InputFile},
			OutputModules: []string{"json"},
		},
		Events: []report.Event{
			report.Info("trim", "trim", fmt.Sprintf("trimmed %d input segment(s) into %d output segment(s) with mode=%s", inputSegmentCount, outputArtifact.SegmentCount(), cfg.Mode)),
			report.Info("trim", "trim-audit", string(auditJSON)),
			report.Info("trim", "validate-output", fmt.Sprintf("validated %d output segment(s)", outputArtifact.SegmentCount())),
			report.Info("output", "json", "wrote transcript JSON"),
		},
	}
	if err := report.WriteJSON(cfg.ReportFile, rpt); err != nil {
		return err
	}

	return nil
}

func orderedIDMapping(mapping map[int]int) []idMapping {
	keys := make([]int, 0, len(mapping))
	for oldID := range mapping {
		keys = append(keys, oldID)
	}
	sort.Ints(keys)

	pairs := make([]idMapping, 0, len(keys))
	for _, oldID := range keys {
		pairs = append(pairs, idMapping{
			OldID: oldID,
			NewID: mapping[oldID],
		})
	}
	return pairs
}