feat: introduce trigger functionality (#27644)

Signed-off-by: lyzno1 <yuanyouhuilyz@gmail.com>
Co-authored-by: Stream <Stream_2@qq.com>
Co-authored-by: lyzno1 <92089059+lyzno1@users.noreply.github.com>
Co-authored-by: zhsama <torvalds@linux.do>
Co-authored-by: Harry <xh001x@hotmail.com>
Co-authored-by: lyzno1 <yuanyouhuilyz@gmail.com>
Co-authored-by: yessenia <yessenia.contact@gmail.com>
Co-authored-by: hjlarry <hjlarry@163.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: WTW0313 <twwu@dify.ai>
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web/app/components/workflow/block-selector/hooks.ts

@@ -1,60 +1,123 @@
 import {
+  useCallback,
+  useEffect,
   useMemo,
   useState,
 } from 'react'
 import { useTranslation } from 'react-i18next'
+import { BLOCKS, START_BLOCKS } from './constants'
 import {
   TabsEnum,
   ToolTypeEnum,
 } from './types'
 
-export const useTabs = (noBlocks?: boolean, noSources?: boolean, noTools?: boolean) => {
+export const useBlocks = () => {
   const { t } = useTranslation()
+
+  return BLOCKS.map((block) => {
+    return {
+      ...block,
+      title: t(`workflow.blocks.${block.type}`),
+    }
+  })
+}
+
+export const useStartBlocks = () => {
+  const { t } = useTranslation()
+
+  return START_BLOCKS.map((block) => {
+    return {
+      ...block,
+      title: t(`workflow.blocks.${block.type}`),
+    }
+  })
+}
+
+export const useTabs = ({
+  noBlocks,
+  noSources,
+  noTools,
+  noStart = true,
+  defaultActiveTab,
+  hasUserInputNode = false,
+  forceEnableStartTab = false, // When true, Start tab remains enabled even if trigger/user input nodes already exist.
+}: {
+  noBlocks?: boolean
+  noSources?: boolean
+  noTools?: boolean
+  noStart?: boolean
+  defaultActiveTab?: TabsEnum
+  hasUserInputNode?: boolean
+  forceEnableStartTab?: boolean
+}) => {
+  const { t } = useTranslation()
+  const shouldShowStartTab = !noStart
+  const shouldDisableStartTab = !forceEnableStartTab && hasUserInputNode
   const tabs = useMemo(() => {
-    return [
-      ...(
-        noBlocks
-          ? []
-          : [
-            {
-              key: TabsEnum.Blocks,
-              name: t('workflow.tabs.blocks'),
-            },
-          ]
-      ),
-      ...(
-        noSources
-          ? []
-          : [
-            {
-              key: TabsEnum.Sources,
-              name: t('workflow.tabs.sources'),
-            },
-          ]
-      ),
-      ...(
-        noTools
-          ? []
-          : [
-            {
-              key: TabsEnum.Tools,
-              name: t('workflow.tabs.tools'),
-            },
-          ]
-      ),
-    ]
-  }, [t, noBlocks, noSources, noTools])
+    const tabConfigs = [{
+      key: TabsEnum.Blocks,
+      name: t('workflow.tabs.blocks'),
+      show: !noBlocks,
+    }, {
+      key: TabsEnum.Sources,
+      name: t('workflow.tabs.sources'),
+      show: !noSources,
+    }, {
+      key: TabsEnum.Tools,
+      name: t('workflow.tabs.tools'),
+      show: !noTools,
+    },
+    {
+      key: TabsEnum.Start,
+      name: t('workflow.tabs.start'),
+      show: shouldShowStartTab,
+      disabled: shouldDisableStartTab,
+    }]
+
+    return tabConfigs.filter(tab => tab.show)
+  }, [t, noBlocks, noSources, noTools, shouldShowStartTab, shouldDisableStartTab])
+
+  const getValidTabKey = useCallback((targetKey?: TabsEnum) => {
+    if (!targetKey)
+      return undefined
+    const tab = tabs.find(tabItem => tabItem.key === targetKey)
+    if (!tab || tab.disabled)
+      return undefined
+    return tab.key
+  }, [tabs])
+
   const initialTab = useMemo(() => {
-    if (noBlocks)
-      return noTools ? TabsEnum.Sources : TabsEnum.Tools
+    const fallbackTab = tabs.find(tab => !tab.disabled)?.key ?? TabsEnum.Blocks
+    const preferredDefault = getValidTabKey(defaultActiveTab)
+    if (preferredDefault)
+      return preferredDefault
 
-    if (noTools)
-      return noBlocks ? TabsEnum.Sources : TabsEnum.Blocks
+    const preferredOrder: TabsEnum[] = []
+    if (!noBlocks)
+      preferredOrder.push(TabsEnum.Blocks)
+    if (!noTools)
+      preferredOrder.push(TabsEnum.Tools)
+    if (!noSources)
+      preferredOrder.push(TabsEnum.Sources)
+    if (!noStart)
+      preferredOrder.push(TabsEnum.Start)
 
-    return TabsEnum.Blocks
-  }, [noBlocks, noSources, noTools])
+    for (const tabKey of preferredOrder) {
+      const validKey = getValidTabKey(tabKey)
+      if (validKey)
+        return validKey
+    }
+
+    return fallbackTab
+  }, [defaultActiveTab, noBlocks, noSources, noTools, noStart, tabs, getValidTabKey])
   const [activeTab, setActiveTab] = useState(initialTab)
 
+  useEffect(() => {
+    const currentTab = tabs.find(tab => tab.key === activeTab)
+    if (!currentTab || currentTab.disabled)
+      setActiveTab(initialTab)
+  }, [tabs, activeTab, initialTab])
+
   return {
     tabs,
     activeTab,