/**
 * Svelte Stage 2 — Generates stores from Stage 1 output.
 */

function pascalCase(str) {
    return str.split(/[.\-_]/).map(p => p.charAt(0).toUpperCase() + p.slice(1)).join('')
}

export function generateSvelteAdapter(schema) {
    const functions = schema['x-mizan-functions'] || []
    const contextGroups = schema['x-mizan-contexts'] || {}
    const mutations = functions.filter(fn => !fn.isContext && !fn.isForm && fn.affects)
    const plainFns = functions.filter(fn => !fn.isContext && !fn.isForm && !fn.affects)

    const lines = [
        '// AUTO-GENERATED by mizan — do not edit',
        '',
        "import { writable, derived, type Readable } from 'svelte/store'",
        "import { registerContext } from '@mizan/runtime'",
        '',
    ]

    // Stage 1 imports
    const stage1Imports = []
    for (const [ctxName] of Object.entries(contextGroups)) {
        const p = pascalCase(ctxName)
        stage1Imports.push(`fetch${p}Context`, `type ${p}ContextData`, `type ${p}ContextParams`)
    }
    for (const fn of [...mutations, ...plainFns]) {
        stage1Imports.push(`call${pascalCase(fn.camelName)}`)
    }
    if (stage1Imports.length > 0) {
        lines.push(`import { ${stage1Imports.join(', ')} } from '../index'`)
        lines.push('')
    }

    // ── Context stores ──────────────────────────────────────────────────

    for (const [ctxName, ctxMeta] of Object.entries(contextGroups)) {
        const p = pascalCase(ctxName)
        const ctxFunctions = functions.filter(fn => fn.isContext === ctxName)
        const paramEntries = Object.entries(ctxMeta.params || {})

        lines.push(`// ${p} context`)

        if (paramEntries.length > 0) {
            lines.push(`export function create${p}Context(params: ${p}ContextParams) {`)
        } else {
            lines.push(`export function create${p}Context() {`)
        }

        lines.push(`    const data = writable<${p}ContextData | null>(null)`)
        lines.push(`    const loading = writable(true)`)
        lines.push('')
        lines.push(`    const refetch = async () => {`)
        lines.push(`        loading.set(true)`)
        if (paramEntries.length > 0) {
            lines.push(`        const result = await fetch${p}Context(params)`)
        } else {
            lines.push(`        const result = await fetch${p}Context({} as any)`)
        }
        lines.push(`        data.set(result)`)
        lines.push(`        loading.set(false)`)
        lines.push(`    }`)
        lines.push('')
        lines.push(`    refetch()`)
        if (paramEntries.length > 0) {
            lines.push(`    const unregister = registerContext('${ctxName}', params, refetch)`)
        } else {
            lines.push(`    const unregister = registerContext('${ctxName}', {}, refetch)`)
        }
        lines.push('')

        // Derived stores for each function
        lines.push(`    return {`)
        lines.push(`        data,`)
        lines.push(`        loading,`)
        for (const fn of ctxFunctions) {
            const camel = fn.camelName
            lines.push(`        ${camel}: derived(data, $d => $d?.${fn.name} ?? null) as Readable<${fn.outputType} | null>,`)
        }
        lines.push(`        destroy: unregister,`)
        lines.push(`    }`)
        lines.push('}')
        lines.push('')
    }

    // ── Mutation + function exports ─────────────────────────────────────

    for (const fn of [...mutations, ...plainFns]) {
        const p = pascalCase(fn.camelName)
        lines.push(`export { call${p} } from '../${fn.affects ? 'mutations' : 'functions'}/${fn.camelName}'`)
    }
    lines.push('')

    return lines.join('\n')
}