import { path, FileSystem, type Logger } from '@servicenow/sdk-build-core'
import { getAttachmentContent } from '../source-artifact-utils'

export type ProjectSourceFiles = {
    // Project-relative paths whose content is read from disk.
    sourceFiles: string[]
}

/**
 * Reads the source-file inputs from `_project.json` for the app source artifact.
 *
 * @returns an empty list when `_project.json` is absent.
 * @throws {Error} if `_project.json` is present but cannot be read or parsed — a corrupt file
 *   fails hard rather than silently producing a build with no editable source, which would
 *   otherwise look identical to the legitimate case where no source files exist.
 */
export function readProjectJsonSourceFiles(fs: FileSystem, metadataDir: string): ProjectSourceFiles {
    const projectJsonPath = path.join(metadataDir, '_project.json')
    if (!FileSystem.existsSync(fs, projectJsonPath)) {
        return { sourceFiles: [] }
    }

    const content = fs.readFileSync(projectJsonPath, { encoding: 'utf-8' }).toString()
    const parsed = JSON.parse(content) as {
        sourceFiles?: string[]
    }
    return {
        sourceFiles: parsed.sourceFiles ?? [],
    }
}

export type SourceArtifactFiles = {
    files: Map<string, Buffer>
    totalSize: number
    skippedFiles: string[]
}

/**
 * Assembles the set of files for the AIUX source artifact from _project.json.
 *
 * Reads `sourceFiles` (project-relative paths) from disk under `projectDir`.
 *
 * @returns the file map, total size, and skipped-file warnings — or `null` when there are
 *   no source files to attach at all.
 * @throws {Error} if the combined size would exceed `MAX_TOTAL_SIZE`, or if `_project.json` is
 *   present but cannot be read or parsed (see {@link readProjectJsonSourceFiles}).
 */
export async function collectSourceArtifactFiles(
    fs: FileSystem,
    {
        metadataDir,
        projectDir,
        useNowPackIgnore = false,
        logger,
    }: { metadataDir: string; projectDir: string; useNowPackIgnore?: boolean; logger?: Logger }
): Promise<SourceArtifactFiles | null> {
    const { sourceFiles } = readProjectJsonSourceFiles(fs, metadataDir)
    if (sourceFiles.length === 0) {
        return null
    }

    return getAttachmentContent(fs, projectDir, sourceFiles, useNowPackIgnore, logger)
}