// Plan assembly, persistence, and preview rendering.
//
// A plan is computed on the MUTATING (target) side: we capture the target's own
// current state, gather live row counts (so data-bearing drops are flagged
// accurately), diff against the source's desired state, fold in can_install_pack
// warnings, and persist the whole thing (plan + desired pack + a precondition hash
// of the target's current state) into _ss_plans under a plan_id. Apply later
// re-checks that precondition hash and refuses if the target drifted since preview
// (optimistic concurrency). Plans are raw/regenerable -- a lost plan just has to be
// re-previewed.

const db    = require("@saltcorn/data/db");
const Table = require("@saltcorn/data/models/table");

const capture = require("./capture");
const diff    = require("./diff");
const rows    = require("./rows");
const { randomUuid } = require("./ids");
const { escapeHtml, ADMIN_URLS } = require("./render");
const { PLAN_STATUS } = require("./constants");

// Keep at most this many recent plans (one row is written per preview).
const PLAN_RETENTION = 200;


// Count rows for every current (non-infra) table so the diff can flag which
// deletes / field-drops actually destroy data. COUNT(*) per table -- acceptable
// for a plan preview. A table that cannot be counted is reported as a warning
// (apply re-counts live before any drop, so the preview is never the last gate).
const gatherRowCounts = async (currentPack, warnings) => {
    const counts = {};
    for (const t of currentPack.tables) {
        const tbl = Table.findOne({ name: t.name });
        try {
            counts[t.name] = tbl ? await tbl.countRows() : 0;
        } catch (e) {
            counts[t.name] = 0;
            warnings.push(`could not count rows of "${t.name}" (${e.message}); its drop is re-checked at apply time`);
        }
    }
    return counts;
};


// Best-effort advisory warnings from Saltcorn's own pre-flight validator.
const collectWarnings = async (desired) => {
    const warnings = [];
    try {
        const pack = require("@saltcorn/admin-models/models/pack");
        const res = await pack.can_install_pack(desired);
        if (res && res.warning) {
            warnings.push(res.warning);
        }
    } catch (e) {
        warnings.push(`could not run pre-flight check: ${e.message}`);
    }
    return warnings;
};


// Compute + persist a plan for making THIS instance's state match `desired`.
// Returns { plan_id, plan }.
const buildPlan = async ({ peerRow, env, desired, desiredHash, sourceEnvId, direction, extraWarnings, sourceRows }) => {
    // NEVER trust the sender's sanitization: re-run it on the target before the
    // pack influences the diff or the persisted plan (drops infra tables the peer
    // may have injected, and any non-allow-listed config key).
    desired = capture.sanitizeDesired(desired);
    const current = await capture.buildDesiredState();
    const countWarnings = [];
    const rowCounts = await gatherRowCounts(current.pack, countWarnings);

    const plan = diff.computePlan(desired, current.pack, {
        syncMode:  env.sync_mode,
        onDelete:  env.on_delete,
        rowCounts: rowCounts
    });

    // Reference-row plan (opt-in managed/starter tables only). The counts feed the
    // preview; the source manifest is stashed on the plan so apply can replay it.
    // Note: install_pack must run before rows on apply, so the schema exists.
    const rowManifest = sourceRows || {};
    const rowPreview = await rows.previewRowSync(rowManifest);
    plan.rows = rowPreview;
    plan.sourceRows = rowManifest;
    const rowOps = Object.values(rowPreview.perTable || {}).reduce((a, t) => a + t.inserts + t.updates + t.deletes, 0);
    plan.summary.rows  = rowOps;
    plan.summary.total = (plan.summary.total || 0) + rowOps;

    plan.source_env_id     = sourceEnvId || (peerRow && peerRow.env_id) || null;
    plan.target_env_id     = env.env_id;
    plan.source_hash       = desiredHash;
    plan.precondition_hash = current.hash;
    plan.generated_at      = new Date().toISOString();
    plan.warnings          = plan.warnings.concat(countWarnings, rowPreview.warnings, extraWarnings || [], await collectWarnings(desired));

    const planId = randomUuid();
    const schema = db.getTenantSchemaPrefix();
    await db.query(
        `INSERT INTO ${schema}_ss_plans
            (plan_id, peer_id, source_env_id, direction, desired_pack, plan_json, precondition_hash, source_hash, status, created_at)
         VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10)`,
        [
            planId,
            peerRow ? peerRow.peer_id : null,
            plan.source_env_id,
            direction || "pull",
            JSON.stringify(desired),
            JSON.stringify(plan),
            plan.precondition_hash,
            plan.source_hash,
            PLAN_STATUS.PENDING,
            plan.generated_at
        ]
    );
    // Retention: _ss_plans gets a row on every preview, so cap it to the most recent
    // PLAN_RETENTION (the just-inserted plan is newest, so never pruned). A plan
    // whose restore point is still kept (_ss_rollback) stays too: rollback needs
    // both, so a burst of previews must never cost a recent apply its rollback.
    await db.query(
        `DELETE FROM ${schema}_ss_plans WHERE plan_id NOT IN ` +
        `(SELECT plan_id FROM ${schema}_ss_plans ORDER BY created_at DESC LIMIT ${PLAN_RETENTION}) ` +
        `AND plan_id NOT IN (SELECT plan_id FROM ${schema}_ss_rollback)`
    ).catch(() => {});
    return { plan_id: planId, plan };
};


const loadPlan = async (planId) => {
    const schema = db.getTenantSchemaPrefix();
    const rs = await db.query(`SELECT * FROM ${schema}_ss_plans WHERE plan_id = $1`, [planId]);
    if (rs.rows.length === 0) {
        return null;
    }
    const row = rs.rows[0];
    return {
        plan_id:           row.plan_id,
        peer_id:           row.peer_id,
        source_env_id:     row.source_env_id,
        direction:         row.direction,
        desired:           JSON.parse(row.desired_pack),
        plan:              JSON.parse(row.plan_json),
        precondition_hash: row.precondition_hash,
        source_hash:       row.source_hash,
        status:            row.status,
        claimed_from:      row.claimed_from,
        created_at:        row.created_at
    };
};


// The most recent plans (newest first), optionally only those in `status`: what
// a listing needs, without the (large) desired pack and plan JSON.
const listPlans = async ({ status, limit }) => {
    const schema = db.getTenantSchemaPrefix();
    const where  = status ? "WHERE status = $1" : "";
    const params = status ? [status, limit] : [limit];
    const rs = await db.query(
        `SELECT plan_id, peer_id, source_env_id, direction, precondition_hash, status, claimed_from, created_at ` +
        `FROM ${schema}_ss_plans ${where} ORDER BY created_at DESC LIMIT $${params.length}`,
        params
    );
    return rs.rows;
};


const setPlanStatus = async (planId, status) => {
    const schema = db.getTenantSchemaPrefix();
    await db.query(`UPDATE ${schema}_ss_plans SET status = $1 WHERE plan_id = $2`, [status, planId]);
};


// Atomically move a plan from one of `fromStatuses` to `toStatus`, recording the
// status it left in claimed_from (SET expressions read the row as it was, on
// SQLite and Postgres alike). Returns true only for the single caller that won the
// transition (RETURNING is used because Saltcorn's SQLite query() exposes no
// affected-row count), so a double-submitted apply/rollback cannot run twice.
const claimPlanStatus = async (planId, fromStatuses, toStatus) => {
    const schema = db.getTenantSchemaPrefix();
    const placeholders = fromStatuses.map((_, i) => `$${i + 3}`).join(",");
    const rs = await db.query(
        `UPDATE ${schema}_ss_plans SET status = $1, claimed_from = status WHERE plan_id = $2 AND status IN (${placeholders}) RETURNING plan_id`,
        [toStatus, planId].concat(fromStatuses)
    );
    return rs.rows.length === 1;
};


// The tables whose data a plan's apply drops (whole tables or fields of populated
// tables): each must be named in the apply's `prunable` allow-list to be dropped.
const dataDropTables = (plan) => {
    return [...new Set(plan.destructive.filter((x) => x.dataBearing).map((x) => x.table))];
};


// --- preview rendering (returns an HTML string; the route wraps it) ---

const kindRows = (title, bucket) => {
    const parts = [];
    const list = (label, arr, render) => {
        if (!arr || arr.length === 0) {
            return;
        }
        parts.push(`<div><span class="badge bg-${label === "delete" ? "danger" : label === "rename" ? "info" : label === "create" ? "success" : "secondary"}">${label} ${arr.length}</span> ` +
            arr.map(render).map((s) => `<code>${escapeHtml(s)}</code>`).join(" ") + `</div>`);
    };
    list("create", bucket.create, (e) => e.name || e.key || e.role || JSON.stringify(e).slice(0, 30));
    list("update", bucket.update, (e) => e.name || e.key || (e.to && (e.to.name || e.to.role)) || JSON.stringify(e).slice(0, 30));
    list("delete", bucket.delete, (e) => e.name || e.key || JSON.stringify(e).slice(0, 30));
    list("rename", bucket.rename, (e) => `${e.from} -> ${e.to}`);
    if (parts.length === 0) {
        return "";
    }
    return `<div class="mb-2"><strong>${escapeHtml(title)}</strong>${parts.join("")}</div>`;
};


const renderPlanHtml = (planId, plan, peerLabel) => {
    const s = plan.summary;
    let html = "";
    html += `<p>Plan <code>${escapeHtml(planId)}</code> to make this instance match <strong>${escapeHtml(peerLabel || plan.source_env_id || "source")}</strong> ` +
        `(sync mode <span class="badge bg-info">${escapeHtml(plan.sync_mode)}</span>).</p>`;

    if (diff.isEmptyPlan(plan)) {
        html += `<div class="alert alert-success">Already in sync -- nothing to apply.</div>`;
        return html;
    }

    const chip = (label, n) => n > 0 ? `<span class="badge bg-secondary me-1">${escapeHtml(label)}: ${n}</span>` : "";
    html += `<p>${diff.PLAN_KINDS.concat(["config"]).map((k) => chip(k, s[k])).join("")}</p>`;

    if (plan.destructive.length > 0) {
        const items = plan.destructive.map((x) =>
            `<li>${x.dataBearing ? '<span class="badge bg-danger">DATA</span> ' : ""}${escapeHtml(x.text)}</li>`).join("");
        html += `<div class="alert alert-warning"><strong>Destructive operations (${plan.destructive.length}, ${s.dataBearing} touch data):</strong><ul class="mb-0">${items}</ul></div>`;
    }
    if (plan.warnings.length > 0) {
        html += `<div class="alert alert-info"><strong>Warnings:</strong><ul class="mb-0">${plan.warnings.map((w) => `<li>${escapeHtml(w)}</li>`).join("")}</ul></div>`;
    }

    html += kindRows("Tables", plan.entities.tables);
    // Nested table field/constraint changes.
    for (const u of plan.entities.tables.update) {
        const bits = [];
        const counted = [
            [u.fields.create.length, "+", "field(s)"],
            [u.fields.update.length, "~", "field(s)"],
            [u.fields.delete.length, "-", "field(s)"],
            [u.constraints.add.length, "+", "constraint(s)"],
            [u.constraints.remove.length, "-", "constraint(s)"]
        ];
        if (u.propsChanged) {
            bits.push("table props");
        }
        for (const [n, sign, what] of counted) {
            if (n > 0) {
                bits.push(`${sign}${n} ${what}`);
            }
        }
        html += `<div class="ms-3 text-muted"><code>${escapeHtml(u.name)}</code>: ${escapeHtml(bits.join(", "))}</div>`;
    }
    for (const kind of diff.PLAN_KINDS.filter((k) => k !== "tables")) {
        html += kindRows(kind.replace(/_/g, " "), plan.entities[kind]);
    }
    if (s.config > 0) {
        html += `<div class="mb-2"><strong>Config</strong><div><span class="badge bg-secondary">overwrite ${s.config}</span> <code>${escapeHtml(Object.keys(plan.config.sets).join(", "))}</code></div></div>`;
    }
    if (plan.rows && plan.rows.perTable && Object.keys(plan.rows.perTable).length > 0) {
        const rowBits = Object.entries(plan.rows.perTable)
            .filter(([, c]) => c.inserts + c.updates + c.deletes > 0)
            .map(([name, c]) => `<div><code>${escapeHtml(name)}</code> <span class="badge bg-info">${escapeHtml(c.mode)}</span> ` +
                `+${c.inserts} ~${c.updates} -${c.deletes}</div>`).join("");
        if (rowBits) {
            html += `<div class="mb-2"><strong>Reference rows</strong>${rowBits}</div>`;
        }
    }
    return html;
};


// The apply form. Detected table renames are offered as UNCHECKED checkboxes
// (`confirm_rename`, value = old table name): an unconfirmed rename is applied as
// create + (gated) drop, so a false-positive structural match never moves data.
// Data-bearing drops are listed as text and the admin must TYPE each table name
// into `prunable` (deliberately never pre-filled -- the server matches the typed
// names exactly) and tick `confirm_data` before applyDeletes will drop them.
const renderApplyForm = (planId, plan, csrfHtml) => {
    const renames   = plan.entities.tables.rename;
    const dataDrops = plan.destructive.filter((x) => x.dataBearing);
    const dropNames = dataDropTables(plan);
    let form = `<form method="post" action="${ADMIN_URLS.APPLY}">`;
    form += csrfHtml || "";
    form += `<input type="hidden" name="plan_id" value="${escapeHtml(planId)}">`;
    renames.forEach((r, i) => {
        form += `<div class="form-check mb-2"><input class="form-check-input" type="checkbox" name="confirm_rename" value="${escapeHtml(r.from)}" id="ssRename${i}">` +
            `<label class="form-check-label" for="ssRename${i}">Rename table <code>${escapeHtml(r.from)}</code> to <code>${escapeHtml(r.to)}</code>, keeping its ${r.rowCount} row(s)</label></div>`;
    });
    if (dataDrops.length > 0) {
        form += `<div class="mb-2"><label class="form-label text-danger fw-bold" for="ssPrunable">` +
            `${dataDrops.length} data-bearing drop(s) in: ${dropNames.map((n) => `<code>${escapeHtml(n)}</code>`).join(", ")}. ` +
            `Type the names of the tables you allow to be dropped (comma-separated); their rows will be destroyed:</label>` +
            `<input class="form-control" name="prunable" id="ssPrunable" autocomplete="off"></div>`;
        form += `<div class="form-check mb-3"><input class="form-check-input" type="checkbox" name="confirm_data" value="1" id="ssConfirmData">` +
            `<label class="form-check-label" for="ssConfirmData">I understand this will permanently destroy data in the tables I typed above.</label></div>`;
    }
    form += `<button class="btn btn-danger" type="submit">Apply this plan</button></form>`;
    return form;
};


module.exports = {
    PLAN_RETENTION,
    buildPlan,
    loadPlan,
    listPlans,
    setPlanStatus,
    claimPlanStatus,
    dataDropTables,
    renderPlanHtml,
    renderApplyForm
};