City-Lifeline-Cockpit/tools/city-massing/sample-terrain-offline.mjs

// Sample the original local quantized-mesh DEM directly through Cesium; no dev server or interpolated grid.
import { readFileSync, writeFileSync, existsSync } from 'node:fs'
import { resolve, relative } from 'node:path'
import { createHash } from 'node:crypto'
import { CesiumTerrainProvider, Cartographic, sampleTerrainMostDetailed } from 'cesium'

const planFile = resolve(process.argv[2] || 'tools/city-massing/city/regular-estate/plan.json')
const output = resolve(process.argv[3] || 'tools/city-massing/city/regular-estate/terrain-samples.json')
const dem = resolve(process.env.YUANLING_DEM || 'D:/GIS/GIS/yuanlingDEM')
const plan = JSON.parse(readFileSync(planFile, 'utf8'))
if (!Array.isArray(plan.samples) || !plan.samples.length) throw new Error('Plan has no footprint samples')
const origin = 'https://local-yuanling-dem.invalid/gis/dem/'
const originalFetch = globalThis.fetch
globalThis.fetch = (input, init) => {
    const url = String(input?.url || input)
    if (!url.startsWith(origin)) return originalFetch(input, init)
    const path = resolve(dem, decodeURIComponent(new URL(url).pathname.slice('/gis/dem/'.length)))
    if (relative(dem, path).startsWith('..')) throw new Error(`Unsafe local terrain path: ${url}`)
    if (!existsSync(path)) throw new Error(`Missing original terrain tile: ${path}`)
    return Promise.resolve(
        new Response(readFileSync(path), {
            status: 200,
            headers: { 'Content-Type': path.endsWith('.json') ? 'application/json' : 'application/octet-stream' },
        })
    )
}
try {
    const provider = await CesiumTerrainProvider.fromUrl(origin)
    const heights = []
    let missing = 0
    for (let i = 0; i < plan.samples.length; i += 128) {
        const points = plan.samples.slice(i, i + 128).map((p) => Cartographic.fromDegrees(p.lon, p.lat))
        const values = await sampleTerrainMostDetailed(provider, points, false)
        for (const value of values) {
            // A sample outside the DEM's coverage is recorded as null and reported, never guessed.
            // The seating stage then excludes the specific module instead of failing the whole city.
            if (!Number.isFinite(value.height) || value.height <= 1) {
                missing++
                heights.push(null)
            } else {
                heights.push(value.height)
            }
        }
    }
    const digest = createHash('sha256').update(JSON.stringify(plan.samples)).digest('hex')
    writeFileSync(
        output,
        JSON.stringify(
            {
                source: dem,
                layerJsonSha256: createHash('sha256')
                    .update(readFileSync(resolve(dem, 'layer.json')))
                    .digest('hex'),
                samplesSha256: digest,
                points: plan.samples,
                heights,
                missingSamples: missing,
            },
            null,
            2
        )
    )
    // Extremes by loop: spreading hundreds of thousands of values overflows the call stack.
    let minHeight = null
    let maxHeight = null
    for (const height of heights) {
        if (height === null) continue
        if (minHeight === null || height < minHeight) minHeight = height
        if (maxHeight === null || height > maxHeight) maxHeight = height
    }
    console.log(
        JSON.stringify({
            points: heights.length,
            missingSamples: missing,
            minHeight,
            maxHeight,
            output,
        })
    )
} finally {
    globalThis.fetch = originalFetch
}