package handlers

import (
	"context"
	"database/sql"
	"encoding/json"
	"net/http"
	"strconv"
	"time"

	"github.com/gin-gonic/gin"

	"armature/models"
	"armature/store"
	"armature/workflow"
)

// instanceView is the enriched response for team instance list endpoints.
type instanceView struct {
	ID            string  `json:"id"`
	WorkflowID    string  `json:"workflow_id"`
	WorkflowName  string  `json:"workflow_name"`
	CurrentStage  string  `json:"current_stage"`
	StageName     string  `json:"stage_name"`
	Status        string  `json:"status"`
	StartedBy     string  `json:"started_by"`
	AgeSeconds    int     `json:"age_seconds"`
	SLABreached   bool    `json:"sla_breached"`
	CreatedAt     string  `json:"created_at"`
}

// ── Instance Handlers ───────────────────────

// WorkflowInstanceHandler manages workflow instance HTTP endpoints.
type WorkflowInstanceHandler struct {
	engine *workflow.Engine
	stores store.Stores
}

// NewWorkflowInstanceHandler creates an instance handler.
func NewWorkflowInstanceHandler(engine *workflow.Engine, stores store.Stores) *WorkflowInstanceHandler {
	return &WorkflowInstanceHandler{engine: engine, stores: stores}
}

// Start creates a new workflow instance.
// POST /api/v1/workflows/:id/instances
func (h *WorkflowInstanceHandler) Start(c *gin.Context) {
	workflowID := c.Param("id")
	userID := c.GetString("user_id")

	var body struct {
		Data     json.RawMessage `json:"data"`
		Metadata json.RawMessage `json:"metadata"`
	}
	if err := c.ShouldBindJSON(&body); err != nil && err.Error() != "EOF" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid request body"})
		return
	}
	if len(body.Data) == 0 {
		body.Data = json.RawMessage(`{}`)
	}

	inst, err := h.engine.Start(c.Request.Context(), workflowID, body.Data, userID)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusCreated, inst)
}

// ListInstances returns instances for a workflow.
// GET /api/v1/workflows/:id/instances?status=&limit=&offset=
func (h *WorkflowInstanceHandler) ListInstances(c *gin.Context) {
	workflowID := c.Param("id")
	status := c.Query("status")

	opts := store.ListOptions{}
	if l := c.Query("limit"); l != "" {
		opts.Limit, _ = strconv.Atoi(l)
	}
	if o := c.Query("offset"); o != "" {
		opts.Offset, _ = strconv.Atoi(o)
	}

	result, err := h.stores.Workflows.ListInstances(c.Request.Context(), workflowID, status, opts)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to list instances"})
		return
	}
	if result == nil {
		c.JSON(http.StatusOK, gin.H{"data": []struct{}{}})
		return
	}
	c.JSON(http.StatusOK, gin.H{"data": result})
}

// GetInstance returns a single instance.
// GET /api/v1/workflows/:id/instances/:iid
func (h *WorkflowInstanceHandler) GetInstance(c *gin.Context) {
	inst, err := h.stores.Workflows.GetInstance(c.Request.Context(), c.Param("iid"))
	if err != nil {
		if err == sql.ErrNoRows {
			c.JSON(http.StatusNotFound, gin.H{"error": "instance not found"})
			return
		}
		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
		return
	}
	// Verify it belongs to the requested workflow
	if inst.WorkflowID != c.Param("id") {
		c.JSON(http.StatusNotFound, gin.H{"error": "instance not found"})
		return
	}
	c.JSON(http.StatusOK, inst)
}

// Advance moves an instance to the next stage.
// POST /api/v1/workflows/:id/instances/:iid/advance
func (h *WorkflowInstanceHandler) Advance(c *gin.Context) {
	userID := c.GetString("user_id")

	var body struct {
		Data json.RawMessage `json:"data"`
	}
	if err := c.ShouldBindJSON(&body); err != nil && err.Error() != "EOF" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid request body"})
		return
	}

	inst, err := h.engine.Advance(c.Request.Context(), c.Param("iid"), body.Data, userID)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, inst)
}

// ListTeamInstances returns enriched instances for all workflows owned by a team.
// GET /api/v1/teams/:teamId/workflow-instances?status=&limit=&offset=
func (h *WorkflowInstanceHandler) ListTeamInstances(c *gin.Context) {
	teamID := c.Param("teamId")
	status := c.Query("status")
	if status == "" {
		status = "active" // default to active for monitoring
	}

	opts := store.ListOptions{}
	if l := c.Query("limit"); l != "" {
		opts.Limit, _ = strconv.Atoi(l)
	}
	if o := c.Query("offset"); o != "" {
		opts.Offset, _ = strconv.Atoi(o)
	}
	if opts.Limit == 0 {
		opts.Limit = 50
	}

	result, err := h.stores.Workflows.ListInstancesByTeam(c.Request.Context(), teamID, status, opts)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to list instances"})
		return
	}
	if result == nil {
		c.JSON(http.StatusOK, gin.H{"data": []instanceView{}})
		return
	}
	c.JSON(http.StatusOK, gin.H{"data": h.enrichInstances(c.Request.Context(), result)})
}

// enrichInstances resolves workflow_name, stage_name, sla_breached, and age
// for each instance by looking up the workflow definition and version snapshot.
func (h *WorkflowInstanceHandler) enrichInstances(ctx context.Context, instances []models.WorkflowInstance) []instanceView {
	views := make([]instanceView, 0, len(instances))
	workflowCache := map[string]*models.Workflow{}

	for _, inst := range instances {
		v := instanceView{
			ID:           inst.ID,
			WorkflowID:   inst.WorkflowID,
			CurrentStage: inst.CurrentStage,
			StageName:    inst.CurrentStage, // default
			Status:       inst.Status,
			StartedBy:    inst.StartedBy,
			AgeSeconds:   int(time.Since(inst.CreatedAt).Seconds()),
			CreatedAt:    inst.CreatedAt.Format(time.RFC3339),
		}

		wf, ok := workflowCache[inst.WorkflowID]
		if !ok {
			wf, _ = h.stores.Workflows.GetByID(ctx, inst.WorkflowID)
			workflowCache[inst.WorkflowID] = wf
		}
		if wf != nil {
			v.WorkflowName = wf.Name
		}

		// SLA check from version snapshot
		ver, _ := h.stores.Workflows.GetVersion(ctx, inst.WorkflowID, inst.WorkflowVersion)
		if ver != nil {
			stages, _ := models.ParseSnapshotStages(ver.Snapshot)
			for _, s := range stages {
				if s.Name == inst.CurrentStage {
					v.StageName = s.Name
					if s.SLASeconds != nil && *s.SLASeconds > 0 {
						elapsed := time.Since(inst.StageEnteredAt)
						v.SLABreached = elapsed.Seconds() > float64(*s.SLASeconds)
					}
					break
				}
			}
		}

		views = append(views, v)
	}
	return views
}

// CancelTeamInstance cancels an instance belonging to a team workflow.
// POST /api/v1/teams/:teamId/workflow-instances/:iid/cancel
func (h *WorkflowInstanceHandler) CancelTeamInstance(c *gin.Context) {
	userID := c.GetString("user_id")
	instanceID := c.Param("iid")

	// Verify instance belongs to a workflow owned by this team
	inst, err := h.stores.Workflows.GetInstance(c.Request.Context(), instanceID)
	if err != nil {
		c.JSON(http.StatusNotFound, gin.H{"error": "instance not found"})
		return
	}
	wf, err := h.stores.Workflows.GetByID(c.Request.Context(), inst.WorkflowID)
	if err != nil || wf.TeamID == nil || *wf.TeamID != c.Param("teamId") {
		c.JSON(http.StatusForbidden, gin.H{"error": "instance does not belong to this team"})
		return
	}

	if err := h.engine.Cancel(c.Request.Context(), instanceID, userID); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}
	c.JSON(http.StatusOK, gin.H{"cancelled": true})
}

// Cancel terminates an active instance.
// POST /api/v1/workflows/:id/instances/:iid/cancel
func (h *WorkflowInstanceHandler) Cancel(c *gin.Context) {
	userID := c.GetString("user_id")

	if err := h.engine.Cancel(c.Request.Context(), c.Param("iid"), userID); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{"cancelled": true})
}