package handlers

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

	"github.com/gin-gonic/gin"

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

// assignmentView is the enriched response for assignment list endpoints.
type assignmentView struct {
	models.WorkflowAssignment
	WorkflowID   string `json:"workflow_id"`
	WorkflowName string `json:"workflow_name"`
	StageName    string `json:"stage_name"`
	SLABreached  bool   `json:"sla_breached"`
}

// ── Assignment Handlers ─────────────────────

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

// NewWorkflowAssignmentHandler creates an assignment handler.
func NewWorkflowAssignmentHandler(engine *workflow.Engine, stores store.Stores) *WorkflowAssignmentHandler {
	return &WorkflowAssignmentHandler{engine: engine, stores: stores}
}

// Claim claims an assignment for the current user.
// POST /api/v1/assignments/:id/claim
func (h *WorkflowAssignmentHandler) Claim(c *gin.Context) {
	userID := c.GetString("user_id")
	assignmentID := c.Param("id")
	ctx := c.Request.Context()

	// Claim first, then verify role. Rollback if role check fails.
	if err := h.stores.Workflows.ClaimAssignment(ctx, assignmentID, userID); err != nil {
		c.JSON(http.StatusConflict, gin.H{"error": err.Error()})
		return
	}

	// Role check: find the assignment in user's claimed list and verify role
	claimed, _ := h.stores.Workflows.ListAssignmentsByUser(ctx, userID, models.AssignmentStatusClaimed)
	for _, a := range claimed {
		if a.ID == assignmentID {
			if rerr := workflow.CheckClaimRole(ctx, h.stores, &a, userID); rerr != nil {
				// Rollback: unclaim
				h.stores.Workflows.UnclaimAssignment(ctx, assignmentID)
				c.JSON(http.StatusForbidden, gin.H{"error": rerr.Error()})
				return
			}
			break
		}
	}

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

// Unclaim releases a claimed assignment back to the queue.
// POST /api/v1/assignments/:id/unclaim
func (h *WorkflowAssignmentHandler) Unclaim(c *gin.Context) {
	userID := c.GetString("user_id")
	assignmentID := c.Param("id")

	// Verify current user is the claimer
	userAssignments, err := h.stores.Workflows.ListAssignmentsByUser(c.Request.Context(), userID, models.AssignmentStatusClaimed)
	if err == nil {
		found := false
		for _, a := range userAssignments {
			if a.ID == assignmentID {
				found = true
				break
			}
		}
		if !found {
			c.JSON(http.StatusForbidden, gin.H{"error": "assignment not claimed by you"})
			return
		}
	}

	if err := h.stores.Workflows.UnclaimAssignment(c.Request.Context(), assignmentID); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

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

// Complete marks a claimed assignment as completed.
// POST /api/v1/assignments/:id/complete
func (h *WorkflowAssignmentHandler) Complete(c *gin.Context) {
	userID := c.GetString("user_id")
	assignmentID := c.Param("id")

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

	// Verify current user is the claimer
	userAssignments, err := h.stores.Workflows.ListAssignmentsByUser(c.Request.Context(), userID, models.AssignmentStatusClaimed)
	if err == nil {
		found := false
		for _, a := range userAssignments {
			if a.ID == assignmentID {
				found = true
				break
			}
		}
		if !found {
			c.JSON(http.StatusForbidden, gin.H{"error": "assignment not claimed by you"})
			return
		}
	}

	if err := h.stores.Workflows.CompleteAssignment(c.Request.Context(), assignmentID, body.ReviewData); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	// If the stage has auto_transition, advance the instance.
	// Look up the assignment's instance to get context.
	userAssignments, _ = h.stores.Workflows.ListAssignmentsByUser(c.Request.Context(), userID, models.AssignmentStatusCompleted)
	for _, a := range userAssignments {
		if a.ID == assignmentID {
			// Try to advance — engine will handle validation
			h.engine.Advance(c.Request.Context(), a.InstanceID, body.ReviewData, userID)
			break
		}
	}

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

// Cancel cancels an open assignment.
// POST /api/v1/assignments/:id/cancel
func (h *WorkflowAssignmentHandler) Cancel(c *gin.Context) {
	assignmentID := c.Param("id")

	if err := h.stores.Workflows.CancelAssignment(c.Request.Context(), assignmentID); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

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

// ListByTeam returns enriched assignments for a team.
// GET /api/v1/teams/:teamId/assignments?status=
func (h *WorkflowAssignmentHandler) ListByTeam(c *gin.Context) {
	teamID := c.Param("teamId")
	status := c.Query("status")

	result, err := h.stores.Workflows.ListAssignmentsByTeam(c.Request.Context(), teamID, status)
	if err != nil {
		if err == sql.ErrNoRows {
			c.JSON(http.StatusOK, gin.H{"data": []assignmentView{}})
			return
		}
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to list assignments"})
		return
	}
	if result == nil {
		c.JSON(http.StatusOK, gin.H{"data": []assignmentView{}})
		return
	}
	c.JSON(http.StatusOK, gin.H{"data": h.enrichAssignments(c.Request.Context(), result)})
}

// Assign lets a team admin assign an unassigned assignment to a specific user.
// POST /api/v1/assignments/:id/assign
func (h *WorkflowAssignmentHandler) Assign(c *gin.Context) {
	assignmentID := c.Param("id")
	ctx := c.Request.Context()

	var body struct {
		UserID string `json:"user_id"`
	}
	if err := c.ShouldBindJSON(&body); err != nil || body.UserID == "" {
		c.JSON(http.StatusBadRequest, gin.H{"error": "user_id is required"})
		return
	}

	// Verify the target user exists
	targetUser, err := h.stores.Users.GetByID(ctx, body.UserID)
	if err != nil || targetUser == nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "user not found"})
		return
	}

	// ClaimAssignment sets assigned_to and status=claimed — works for admin assignment
	if err := h.stores.Workflows.ClaimAssignment(ctx, assignmentID, body.UserID); err != nil {
		c.JSON(http.StatusConflict, gin.H{"error": err.Error()})
		return
	}

	c.JSON(http.StatusOK, gin.H{"assigned": true, "assigned_to": body.UserID})
}

// ListMine returns enriched assignments claimed by or assigned to the current user.
// GET /api/v1/assignments/mine?status=
func (h *WorkflowAssignmentHandler) ListMine(c *gin.Context) {
	userID := c.GetString("user_id")
	status := c.Query("status")

	result, err := h.stores.Workflows.ListAssignmentsByUser(c.Request.Context(), userID, status)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to list assignments"})
		return
	}
	if result == nil {
		c.JSON(http.StatusOK, gin.H{"data": []assignmentView{}})
		return
	}
	c.JSON(http.StatusOK, gin.H{"data": h.enrichAssignments(c.Request.Context(), result)})
}

// enrichAssignments resolves workflow_name, stage_name, and sla_breached
// for each assignment by looking up instance → workflow → stage snapshot.
func (h *WorkflowAssignmentHandler) enrichAssignments(ctx context.Context, assignments []models.WorkflowAssignment) []assignmentView {
	views := make([]assignmentView, 0, len(assignments))

	// Cache lookups to avoid repeated DB hits for the same workflow/instance
	instanceCache := map[string]*models.WorkflowInstance{}
	workflowCache := map[string]*models.Workflow{}

	for _, a := range assignments {
		v := assignmentView{WorkflowAssignment: a}

		// Resolve instance → workflow
		inst, ok := instanceCache[a.InstanceID]
		if !ok {
			inst, _ = h.stores.Workflows.GetInstance(ctx, a.InstanceID)
			instanceCache[a.InstanceID] = inst
		}

		if inst != nil {
			v.WorkflowID = inst.WorkflowID

			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
			}

			// Resolve stage name and SLA from the published version snapshot
			ver, _ := h.stores.Workflows.GetVersion(ctx, inst.WorkflowID, inst.WorkflowVersion)
			if ver != nil {
				stages := parseSnapshotStagesForEnrich(ver.Snapshot)
				for _, s := range stages {
					if s.Name == a.Stage {
						v.StageName = s.Name
						if s.SLASeconds != nil && *s.SLASeconds > 0 {
							elapsed := time.Since(a.CreatedAt)
							v.SLABreached = elapsed.Seconds() > float64(*s.SLASeconds)
						}
						break
					}
				}
			}
		}

		// Fallback: use stage field as stage_name if not resolved
		if v.StageName == "" {
			v.StageName = a.Stage
		}

		views = append(views, v)
	}

	return views
}

// parseSnapshotStagesForEnrich is a lightweight stage parser for enrichment.
func parseSnapshotStagesForEnrich(snapshot json.RawMessage) []models.WorkflowStage {
	var wrapped struct {
		Stages []models.WorkflowStage `json:"stages"`
	}
	if err := json.Unmarshal(snapshot, &wrapped); err == nil && len(wrapped.Stages) > 0 {
		return wrapped.Stages
	}
	var stages []models.WorkflowStage
	json.Unmarshal(snapshot, &stages)
	return stages
}