chore(coderd/database/migrations): migrate tasks to new data model (#20434)

Updates coder/internal#976
Closes coder/internal#1078

coderd/database/migrations/000387_migrate_task_workspaces.up.sql

@@ -0,0 +1,113 @@
+-- Migrate existing task workspaces to the new tasks data model. This migration
+-- identifies workspaces that were created as tasks (has_ai_task = true) and
+-- populates the tasks and task_workspace_apps tables with their data.
+
+-- Step 1: Create tasks from workspaces with has_ai_task TRUE in their latest build.
+INSERT INTO tasks (
+	id,
+	organization_id,
+	owner_id,
+	name,
+	workspace_id,
+	template_version_id,
+	template_parameters,
+	prompt,
+	created_at,
+	deleted_at
+)
+SELECT
+	gen_random_uuid() AS id,
+	w.organization_id,
+	w.owner_id,
+	w.name,
+	w.id AS workspace_id,
+	latest_task_build.template_version_id,
+	COALESCE(params.template_parameters, '{}'::jsonb) AS template_parameters,
+	COALESCE(ai_prompt.value, '') AS prompt,
+	w.created_at,
+	CASE WHEN w.deleted = true THEN w.deleting_at ELSE NULL END AS deleted_at
+FROM workspaces w
+INNER JOIN LATERAL (
+	-- Find the latest build for this workspace that has has_ai_task = true.
+	SELECT
+		wb.template_version_id
+	FROM workspace_builds wb
+	WHERE wb.workspace_id = w.id
+		AND wb.has_ai_task = true
+	ORDER BY wb.build_number DESC
+	LIMIT 1
+) latest_task_build ON true
+LEFT JOIN LATERAL (
+	-- Find the latest build that has a non-empty AI Prompt parameter.
+	SELECT
+		wb.id
+	FROM workspace_builds wb
+	WHERE wb.workspace_id = w.id
+		AND EXISTS (
+			SELECT 1
+			FROM workspace_build_parameters wbp
+			WHERE wbp.workspace_build_id = wb.id
+				AND wbp.name = 'AI Prompt'
+				AND wbp.value != ''
+		)
+	ORDER BY wb.build_number DESC
+	LIMIT 1
+) latest_prompt_build ON true
+LEFT JOIN LATERAL (
+	-- Extract the AI Prompt parameter value from the prompt build.
+	SELECT wbp.value
+	FROM workspace_build_parameters wbp
+	WHERE wbp.workspace_build_id = latest_prompt_build.id
+		AND wbp.name = 'AI Prompt'
+	LIMIT 1
+) ai_prompt ON true
+LEFT JOIN LATERAL (
+	-- Aggregate all other parameters (excluding AI Prompt) from the prompt build.
+	SELECT jsonb_object_agg(wbp.name, wbp.value) AS template_parameters
+	FROM workspace_build_parameters wbp
+	WHERE wbp.workspace_build_id = latest_prompt_build.id
+		AND wbp.name != 'AI Prompt'
+) params ON true
+WHERE
+	-- Skip deleted workspaces because of duplicate name.
+	w.deleted = false
+	-- Safe-guard, do not create tasks for workspaces that are already tasks.
+	AND NOT EXISTS (
+		SELECT 1
+		FROM tasks t
+		WHERE t.workspace_id = w.id
+	);
+
+-- Step 2: Populate task_workspace_apps table with build/agent/app information.
+INSERT INTO task_workspace_apps (
+	task_id,
+	workspace_build_number,
+	workspace_agent_id,
+	workspace_app_id
+)
+SELECT
+	t.id AS task_id,
+	latest_build.build_number AS workspace_build_number,
+	sidebar_app.agent_id AS workspace_agent_id,
+	sidebar_app.id AS workspace_app_id
+FROM tasks t
+INNER JOIN LATERAL (
+	-- Find the latest build for this tasks workspace.
+	SELECT
+		wb.build_number,
+		wb.ai_task_sidebar_app_id
+	FROM workspace_builds wb
+	WHERE wb.workspace_id = t.workspace_id
+	ORDER BY wb.build_number DESC
+	LIMIT 1
+) latest_build ON true
+-- Get the sidebar app (optional, can be NULL).
+LEFT JOIN workspace_apps sidebar_app
+	ON sidebar_app.id = latest_build.ai_task_sidebar_app_id
+WHERE
+	-- Safe-guard, do not create for existing tasks.
+	NOT EXISTS (
+		SELECT 1
+		FROM task_workspace_apps twa
+		WHERE twa.task_id = t.id
+	);