package tools

import (
	"context"
	"log/slog"
	"sync"
	"time"

	"github.com/google/uuid"
	"github.com/modelcontextprotocol/go-sdk/mcp"
	"golang.org/x/sync/semaphore"

	"git.warky.dev/wdevs/amcs/internal/ai"
	"git.warky.dev/wdevs/amcs/internal/config"
	"git.warky.dev/wdevs/amcs/internal/metadata"
	"git.warky.dev/wdevs/amcs/internal/session"
	"git.warky.dev/wdevs/amcs/internal/store"
	thoughttypes "git.warky.dev/wdevs/amcs/internal/types"
)

const metadataRetryConcurrency = 4

type MetadataRetryer struct {
	backgroundCtx   context.Context
	store           *store.DB
	provider        ai.Provider
	capture         config.CaptureConfig
	sessions        *session.ActiveProjects
	metadataTimeout time.Duration
	logger          *slog.Logger
}

type RetryMetadataTool struct {
	retryer *MetadataRetryer
}

type RetryMetadataInput struct {
	Project         string `json:"project,omitempty" jsonschema:"optional project name or id to scope the retry"`
	Limit           int    `json:"limit,omitempty" jsonschema:"maximum number of thoughts to process in one call; defaults to 100"`
	IncludeArchived bool   `json:"include_archived,omitempty" jsonschema:"whether to include archived thoughts; defaults to false"`
	OlderThanDays   int    `json:"older_than_days,omitempty" jsonschema:"only retry thoughts whose last metadata attempt was at least N days ago; 0 means no restriction"`
	DryRun          bool   `json:"dry_run,omitempty" jsonschema:"report counts without retrying metadata extraction"`
}

type RetryMetadataFailure struct {
	ID    string `json:"id"`
	Error string `json:"error"`
}

type RetryMetadataOutput struct {
	Scanned  int                    `json:"scanned"`
	Retried  int                    `json:"retried"`
	Updated  int                    `json:"updated"`
	Skipped  int                    `json:"skipped"`
	Failed   int                    `json:"failed"`
	DryRun   bool                   `json:"dry_run"`
	Failures []RetryMetadataFailure `json:"failures,omitempty"`
}

func NewMetadataRetryer(backgroundCtx context.Context, db *store.DB, provider ai.Provider, capture config.CaptureConfig, metadataTimeout time.Duration, sessions *session.ActiveProjects, logger *slog.Logger) *MetadataRetryer {
	if backgroundCtx == nil {
		backgroundCtx = context.Background()
	}
	return &MetadataRetryer{
		backgroundCtx:   backgroundCtx,
		store:           db,
		provider:        provider,
		capture:         capture,
		sessions:        sessions,
		metadataTimeout: metadataTimeout,
		logger:          logger,
	}
}

func NewRetryMetadataTool(retryer *MetadataRetryer) *RetryMetadataTool {
	return &RetryMetadataTool{retryer: retryer}
}

func (t *RetryMetadataTool) Handle(ctx context.Context, req *mcp.CallToolRequest, in RetryMetadataInput) (*mcp.CallToolResult, RetryMetadataOutput, error) {
	return t.retryer.Handle(ctx, req, in)
}

func (r *MetadataRetryer) QueueThought(id uuid.UUID) {
	go func() {
		attemptCtx := r.backgroundCtx
		if r.metadataTimeout > 0 {
			var cancel context.CancelFunc
			attemptCtx, cancel = context.WithTimeout(r.backgroundCtx, r.metadataTimeout)
			defer cancel()
		}
		if _, err := r.retryOne(attemptCtx, id); err != nil {
			r.logger.Warn("background metadata retry failed", slog.String("thought_id", id.String()), slog.String("error", err.Error()))
		}
	}()
}

func (r *MetadataRetryer) Handle(ctx context.Context, req *mcp.CallToolRequest, in RetryMetadataInput) (*mcp.CallToolResult, RetryMetadataOutput, error) {
	limit := in.Limit
	if limit <= 0 {
		limit = 100
	}

	project, err := resolveProject(ctx, r.store, r.sessions, req, in.Project, false)
	if err != nil {
		return nil, RetryMetadataOutput{}, err
	}

	var projectID *uuid.UUID
	if project != nil {
		projectID = &project.ID
	}

	thoughts, err := r.store.ListThoughtsPendingMetadataRetry(ctx, limit, projectID, in.IncludeArchived, in.OlderThanDays)
	if err != nil {
		return nil, RetryMetadataOutput{}, err
	}

	out := RetryMetadataOutput{
		Scanned: len(thoughts),
		DryRun:  in.DryRun,
	}
	if in.DryRun || len(thoughts) == 0 {
		return nil, out, nil
	}

	sem := semaphore.NewWeighted(metadataRetryConcurrency)
	var mu sync.Mutex
	var wg sync.WaitGroup

	for _, thought := range thoughts {
		if ctx.Err() != nil {
			break
		}
		if err := sem.Acquire(ctx, 1); err != nil {
			break
		}

		wg.Add(1)
		go func(thought thoughttypes.Thought) {
			defer wg.Done()
			defer sem.Release(1)

			mu.Lock()
			out.Retried++
			mu.Unlock()

			updated, err := r.retryOne(ctx, thought.ID)
			if err != nil {
				mu.Lock()
				out.Failures = append(out.Failures, RetryMetadataFailure{ID: thought.ID.String(), Error: err.Error()})
				mu.Unlock()
				return
			}
			if updated {
				mu.Lock()
				out.Updated++
				mu.Unlock()
				return
			}

			mu.Lock()
			out.Skipped++
			mu.Unlock()
		}(thought)
	}

	wg.Wait()
	out.Failed = len(out.Failures)

	return nil, out, nil
}

func (r *MetadataRetryer) retryOne(ctx context.Context, id uuid.UUID) (bool, error) {
	thought, err := r.store.GetThought(ctx, id)
	if err != nil {
		return false, err
	}
	if thought.Metadata.MetadataStatus == metadata.MetadataStatusComplete {
		return false, nil
	}

	attemptCtx := ctx
	if r.metadataTimeout > 0 {
		var cancel context.CancelFunc
		attemptCtx, cancel = context.WithTimeout(ctx, r.metadataTimeout)
		defer cancel()
	}

	attemptedAt := time.Now().UTC()
	extracted, extractErr := r.provider.ExtractMetadata(attemptCtx, thought.Content)
	if extractErr != nil {
		failedMetadata := metadata.MarkMetadataFailed(thought.Metadata, r.capture, attemptedAt, extractErr)
		if _, updateErr := r.store.UpdateThoughtMetadata(ctx, thought.ID, failedMetadata); updateErr != nil {
			return false, updateErr
		}
		return false, extractErr
	}

	completedMetadata := metadata.MarkMetadataComplete(extracted, r.capture, attemptedAt)
	completedMetadata.Attachments = thought.Metadata.Attachments
	if _, updateErr := r.store.UpdateThoughtMetadata(ctx, thought.ID, completedMetadata); updateErr != nil {
		return false, updateErr
	}

	return true, nil
}