package main

import (
	"context"
	"fmt"
	"os"
	"strings"
	"time"

	"github.com/spf13/cobra"
	"github.com/steveyegge/beads/internal/storage"
	"github.com/steveyegge/beads/internal/storage/sqlite"
	"github.com/steveyegge/beads/internal/types"
	"github.com/steveyegge/beads/internal/ui"
	"github.com/steveyegge/beads/internal/utils"
)

var molSquashCmd = &cobra.Command{
	Use:   "squash <molecule-id>",
	Short: "Compress molecule execution into a digest",
	Long: `Squash a molecule's ephemeral children into a single digest issue.

This command collects all ephemeral child issues of a molecule (Ephemeral=true),
generates a summary digest, and promotes the wisps to persistent by
clearing their Wisp flag (or optionally deletes them).

The squash operation:
  1. Loads the molecule and all its children
  2. Filters to only wisps (ephemeral issues with Ephemeral=true)
  3. Generates a digest (summary of work done)
  4. Creates a permanent digest issue (Ephemeral=false)
  5. Clears Wisp flag on children (promotes to persistent)
     OR deletes them with --delete-children

AGENT INTEGRATION:
Use --summary to provide an AI-generated summary. This keeps bd as a pure
tool - the calling agent (Gas Town polecat, Claude Code, etc.) is responsible
for generating intelligent summaries. Without --summary, a basic concatenation
of child issue content is used.

This is part of the wisp workflow: spawn creates wisps,
execution happens, squash compresses the trace into an outcome (digest).

Example:
  bd mol squash bd-abc123                    # Squash and promote children
  bd mol squash bd-abc123 --dry-run          # Preview what would be squashed
  bd mol squash bd-abc123 --delete-children  # Delete wisps after digest
  bd mol squash bd-abc123 --summary "Agent-generated summary of work done"`,
	Args: cobra.ExactArgs(1),
	Run:  runMolSquash,
}

// SquashResult holds the result of a squash operation
type SquashResult struct {
	MoleculeID    string   `json:"molecule_id"`
	DigestID      string   `json:"digest_id"`
	SquashedIDs   []string `json:"squashed_ids"`
	SquashedCount int      `json:"squashed_count"`
	DeletedCount  int      `json:"deleted_count"`
	KeptChildren  bool     `json:"kept_children"`
	WispSquash    bool     `json:"wisp_squash,omitempty"` // True if this was a wisp→digest squash
}

func runMolSquash(cmd *cobra.Command, args []string) {
	CheckReadonly("mol squash")

	ctx := rootCtx

	// mol squash requires direct store access (daemon auto-bypassed for wisp ops)
	if store == nil {
		fmt.Fprintf(os.Stderr, "Error: no database connection\n")
		fmt.Fprintf(os.Stderr, "Hint: run 'bd init' or 'bd import' to initialize the database\n")
		os.Exit(1)
	}

	dryRun, _ := cmd.Flags().GetBool("dry-run")
	keepChildren, _ := cmd.Flags().GetBool("keep-children")
	summary, _ := cmd.Flags().GetString("summary")

	// Resolve molecule ID in main store
	moleculeID, err := utils.ResolvePartialID(ctx, store, args[0])
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error resolving molecule ID %s: %v\n", args[0], err)
		os.Exit(1)
	}

	// Load the molecule subgraph from main store
	subgraph, err := loadTemplateSubgraph(ctx, store, moleculeID)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error loading molecule: %v\n", err)
		os.Exit(1)
	}

	// Filter to only ephemeral children (exclude root)
	var wispChildren []*types.Issue
	for _, issue := range subgraph.Issues {
		if issue.ID == subgraph.Root.ID {
			continue // Skip root
		}
		if issue.Ephemeral {
			wispChildren = append(wispChildren, issue)
		}
	}

	if len(wispChildren) == 0 {
		if jsonOutput {
			outputJSON(SquashResult{
				MoleculeID:    moleculeID,
				SquashedCount: 0,
			})
		} else {
			fmt.Printf("No ephemeral children found for molecule %s\n", moleculeID)
		}
		return
	}

	if dryRun {
		fmt.Printf("\nDry run: would squash %d ephemeral children of %s\n\n", len(wispChildren), moleculeID)
		fmt.Printf("Root: %s\n", subgraph.Root.Title)
		fmt.Printf("\nWisp children to squash:\n")
		for _, issue := range wispChildren {
			status := string(issue.Status)
			fmt.Printf("  - [%s] %s (%s)\n", status, issue.Title, issue.ID)
		}
		fmt.Printf("\nDigest preview:\n")
		digest := generateDigest(subgraph.Root, wispChildren)
		// Show first 500 chars of digest
		if len(digest) > 500 {
			fmt.Printf("%s...\n", digest[:500])
		} else {
			fmt.Printf("%s\n", digest)
		}
		if keepChildren {
			fmt.Printf("\n--keep-children: children would NOT be deleted\n")
		} else {
			fmt.Printf("\nChildren would be deleted after digest creation.\n")
		}
		return
	}

	// Perform the squash
	result, err := squashMolecule(ctx, store, subgraph.Root, wispChildren, keepChildren, summary, actor)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error squashing molecule: %v\n", err)
		os.Exit(1)
	}

	// Schedule auto-flush
	markDirtyAndScheduleFlush()

	if jsonOutput {
		outputJSON(result)
		return
	}

	fmt.Printf("%s Squashed molecule: %d children → 1 digest\n", ui.RenderPass("✓"), result.SquashedCount)
	fmt.Printf("  Digest ID: %s\n", result.DigestID)
	if result.DeletedCount > 0 {
		fmt.Printf("  Deleted: %d wisps\n", result.DeletedCount)
	} else if result.KeptChildren {
		fmt.Printf("  Children preserved (--keep-children)\n")
	}
}

// generateDigest creates a summary from the molecule execution
// Tier 2: Simple concatenation of titles and descriptions
// Tier 3 (future): AI-powered summarization using Haiku
func generateDigest(root *types.Issue, children []*types.Issue) string {
	var sb strings.Builder

	sb.WriteString("## Molecule Execution Summary\n\n")
	sb.WriteString(fmt.Sprintf("**Molecule**: %s\n", root.Title))
	sb.WriteString(fmt.Sprintf("**Steps**: %d\n\n", len(children)))

	// Count completed vs other statuses
	completed := 0
	inProgress := 0
	for _, c := range children {
		switch c.Status {
		case types.StatusClosed:
			completed++
		case types.StatusInProgress:
			inProgress++
		}
	}
	sb.WriteString(fmt.Sprintf("**Completed**: %d/%d\n", completed, len(children)))
	if inProgress > 0 {
		sb.WriteString(fmt.Sprintf("**In Progress**: %d\n", inProgress))
	}
	sb.WriteString("\n---\n\n")

	// List each step with its outcome
	sb.WriteString("### Steps\n\n")
	for i, child := range children {
		status := string(child.Status)
		sb.WriteString(fmt.Sprintf("%d. **[%s]** %s\n", i+1, status, child.Title))
		if child.Description != "" {
			// Include first 200 chars of description
			desc := child.Description
			if len(desc) > 200 {
				desc = desc[:200] + "..."
			}
			sb.WriteString(fmt.Sprintf("   %s\n", desc))
		}
		if child.CloseReason != "" {
			sb.WriteString(fmt.Sprintf("   *Outcome: %s*\n", child.CloseReason))
		}
		sb.WriteString("\n")
	}

	return sb.String()
}

// squashMolecule performs the squash operation
// If summary is provided (non-empty), it's used as the digest content.
// Otherwise, generateDigest() creates a basic concatenation.
// This enables agents to provide AI-generated summaries while keeping bd as a pure tool.
func squashMolecule(ctx context.Context, s storage.Storage, root *types.Issue, children []*types.Issue, keepChildren bool, summary string, actorName string) (*SquashResult, error) {
	if s == nil {
		return nil, fmt.Errorf("no database connection")
	}

	// Collect child IDs
	childIDs := make([]string, len(children))
	for i, c := range children {
		childIDs[i] = c.ID
	}

	// Use agent-provided summary if available, otherwise generate basic digest
	var digestContent string
	if summary != "" {
		digestContent = summary
	} else {
		digestContent = generateDigest(root, children)
	}

	// Create digest issue (permanent, not a wisp)
	now := time.Now()
	digestIssue := &types.Issue{
		Title:       fmt.Sprintf("Digest: %s", root.Title),
		Description: digestContent,
		Status:      types.StatusClosed,
		CloseReason: fmt.Sprintf("Squashed from %d wisps", len(children)),
		Priority:    root.Priority,
		IssueType:   types.TypeTask,
		Ephemeral:        false, // Digest is permanent, not a wisp
		ClosedAt:    &now,
	}

	result := &SquashResult{
		MoleculeID:    root.ID,
		SquashedIDs:   childIDs,
		SquashedCount: len(children),
		KeptChildren:  keepChildren,
	}

	// Use transaction for atomicity
	err := s.RunInTransaction(ctx, func(tx storage.Transaction) error {
		// Create digest issue
		if err := tx.CreateIssue(ctx, digestIssue, actorName); err != nil {
			return fmt.Errorf("failed to create digest issue: %w", err)
		}
		result.DigestID = digestIssue.ID

		// Link digest to root as parent-child
		dep := &types.Dependency{
			IssueID:     digestIssue.ID,
			DependsOnID: root.ID,
			Type:        types.DepParentChild,
		}
		if err := tx.AddDependency(ctx, dep, actorName); err != nil {
			return fmt.Errorf("failed to link digest to root: %w", err)
		}

		return nil
	})

	if err != nil {
		return nil, err
	}

	// Delete ephemeral children (outside transaction for better error handling)
	if !keepChildren {
		deleted, err := deleteWispChildren(ctx, s, childIDs)
		if err != nil {
			// Log but don't fail - digest was created successfully
			fmt.Fprintf(os.Stderr, "Warning: failed to delete some children: %v\n", err)
		}
		result.DeletedCount = deleted
	}

	return result, nil
}

// deleteWispChildren removes the wisp issues from the database
func deleteWispChildren(ctx context.Context, s storage.Storage, ids []string) (int, error) {
	// Type assert to SQLite storage for delete access
	d, ok := s.(*sqlite.SQLiteStorage)
	if !ok {
		return 0, fmt.Errorf("delete not supported by this storage backend")
	}

	deleted := 0
	var lastErr error
	for _, id := range ids {
		if err := d.DeleteIssue(ctx, id); err != nil {
			lastErr = err
			continue
		}
		deleted++
	}

	return deleted, lastErr
}

func init() {
	molSquashCmd.Flags().Bool("dry-run", false, "Preview what would be squashed")
	molSquashCmd.Flags().Bool("keep-children", false, "Don't delete ephemeral children after squash")
	molSquashCmd.Flags().String("summary", "", "Agent-provided summary (bypasses auto-generation)")

	molCmd.AddCommand(molSquashCmd)
}
